indentation tests of aluminium honeycombs

12
Journal of Physics: Conference Series OPEN ACCESS Indentation tests of aluminium honeycombs To cite this article: A Ashab et al 2013 J. Phys.: Conf. Ser. 451 012003 View the article online for updates and enhancements. You may also like Band gap analysis of star-shaped honeycombs with varied Poisson’s ratio J Meng, Z Deng, K Zhang et al. - Doubly unusual 3D lattice honeycomb displaying simultaneous negative and zero Poisson’s ratio properties Yu Chen, Bin-Bin Zheng, Ming-Hui Fu et al. - Study of a zero Poisson’s ratio honeycomb used for flexible skin Jiaxin Rong and Li Zhou - This content was downloaded from IP address 83.249.211.238 on 17/11/2021 at 03:06

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Journal of Physics Conference Series

OPEN ACCESS

Indentation tests of aluminium honeycombsTo cite this article A Ashab et al 2013 J Phys Conf Ser 451 012003

View the article online for updates and enhancements

You may also likeBand gap analysis of star-shapedhoneycombs with varied Poissonrsquos ratioJ Meng Z Deng K Zhang et al

-

Doubly unusual 3D lattice honeycombdisplaying simultaneous negative and zeroPoissonrsquos ratio propertiesYu Chen Bin-Bin Zheng Ming-Hui Fu etal

-

Study of a zero Poissonrsquos ratio honeycombused for flexible skinJiaxin Rong and Li Zhou

-

This content was downloaded from IP address 83249211238 on 17112021 at 0306

Indentation tests of aluminium honeycombs

A Ashab1 Y C Wong1 G Lu2 and D Ruan1 3 1Faculty of Engineering and Industrial Sciences Swinburne University of Technology Hawthorn VIC 3122 Australia 2School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore 639798 Email druanswineduau

Abstract Aluminium honeycomb is a type of cellular material which has high strength to weigh ratio and is a good energy absorber They are used as structural components in various engineering applications Comprehensive study has been conducted on the compressive behavior of aluminium honeycombs However the research of aluminium honeycombs subjected to other type of loading such as indentation is still limited In this paper quasi-static and dynamic indentation tests were conducted to study the deformation and energy absorption of three types of HEXCELLreg aluminium honeycombs with different cell sizes and cell wall thicknesses Quasi-static tests were conducted by using a universal MTS machine at velocities of 005 mms 05 mms and 5 mms respectively Dynamic tests were conducted by using a high speed INSTRON machine at a velocity of 5 ms Force-displacement curves were plotted in which the total energy absorbed was calculated The deformation of aluminium honeycombs in indentation tests includes the compression of honeycomb cells under the indenter and tearing of honeycomb cell walls along the indenter edges The energy dissipated in compression and tearing were calculated and discussed The effects of cell size cell wall thickness and loading velocity or strain rate on the plateau stress and energy absorption were analyzed

1 Introduction Aluminium honeycombs are lightweight and have good energy absorption capabilities They are widely used as core materials in various fields of engineering such as aerospace and automotive because of their extensive engineering properties Some of the applications of aluminium honeycombs are landing gear door and flaps of aircraft For example crushable aluminium honeycombs had been used in the Apollo 11 lading module The large plastic deformation in hexagonal honeycombs is the main energy absorption region It has been demonstrated that the plastic deformation and energy absorption characteristics of aluminium honeycombs depends on both the geometrical configuration and mechanical properties of cell wall materials [1 2] Cell size cell wall thickness and strain rate are important parameters that affect plateau stress as well as impact response of aluminium honeycombs Gibson and Ashby [1] pointed out that the deformation pattern and compressive strength varied with the direction of loads for example aluminium honeycombs strength is higher in the out-of plane direction compared with the two in-plane directions A schematic diagram of aluminum honeycomb structure is shown in Figure 1 The cell wall thickness t and 2t are known as single wall and double wall respectively The cell edge length is denoted as l while h is the thickness of honeycomb ______________________________ 3 To whom any correspondence should be addressed

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

Content from this work may be used under the terms of the Creative Commons Attribution 30 licence Any further distributionof this work must maintain attribution to the author(s) and the title of the work journal citation and DOI

Published under licence by IOP Publishing Ltd 1

Buckling folding stretching de-bonding and tearing are the major failure mechanisms of aluminium honeycombs Many researchers [3-6] studied aluminium honeycombs experimentally numerically and theoretically to characterize their crushing behaviour and failure mechanism under both quasi-static and dynamic compression Zhou and Mayer [7] conducted compressive and indentation punch tests on two types of aluminium honeycombs with different cell sizes (64 mm and 191 mm respectively) In compression the honeycomb with larger cell size was found to be strain rate dependent while the 3honeycomb with smaller cell size did not show evident strain rate sensitivity Quasi-static tearing strength of honeycomb was defined measured and calculated from the indentation punch tests Two types of honeycombs deformed differently However since no dynamic indentation punch test was conducted the strain rate sensitivity is still unknown

Figure 1 Schematic diagram of an aluminium honeycomb structure

In the present paper out-of-plane quasi-static and dynamic indentations and compressive tests have been conducted using MTS and high speed INSTRON machines to investigate tearing and compressive strengths Three types of aluminium honeycombs having different cell sizes and wall thicknesses have been used in the experiment For quasi-static tests velocities of 005 mms 05 mms and 5 mms were used and for dynamic tests a velocity of 5 ms was used The tearing and compressive strengths were calculated from the experimental results and the dependency of the dissipated energy on the loading speed was also discussed

2 Experiments 21 Specification of materials and specimens HEXCELLreg aluminium honeycombs with different cell sizes and wall thicknesses were used in the experiments The specific material used is aluminium alloy 5052 with an H39 temper The properties of three types of honeycombs are listed in Table 1 Each of the hexagonal honeycomb cell contain four single walls and two adjacent double walls of which all the cells are inter-connected to each other The thickness of the double walls is twice of the single wall thickness In compressive tests honeycomb specimens used were 90 mm times 90 mm In indentation tests honeycomb specimens used were 180 mm times 180 mm All honeycomb specimens were 50 mm in height

The dimension of the indenter used in the indentation tests was a 90 mm times 90 mm which covers at least 9 times 9 cells of all types of honeycombs studied This cross-section of the indenter used was to ensure almost uniform compression of honeycomb cells A circular plate with holes was used as fixed

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

2

platen where the honeycomb specimen was placed In order to avoid specimen dis-connected with the platen rubber bands double sided tape was used to fasten the specimen in the platen The holes in the circular plate are for the entrapped air to escape during testing Therefore in this experiment the effect of entrapped air could be ignored

Table 1 HEXCELLreg 5052 aluminium hexagonal honeycomb Name Material Cell

size D (mm)

Cell wall thickness t

(mm)

Nominal Density 120646 (kgm3)

Modulus (GPa)

Crush Strength (MPa)

No of cells

covered by

Indenter A 31-316-5052-001N 4763 00254 4966 052 090 19times19

B 42-38-5052-003N 9525 00762 6728 093 152 9times9

C 45-18-5052-001N 3175 00254 7209 103 179 28times28

22 Quasi-static tests

Figure 2 Out-of-plane quasi-static indentation tests conducted on the 50 kN MTS machine

Out-of-plane quasi-static tests were conducted on an MTS machine (Model LPS504) which had a load capacity of 50 kN that could reach a velocity of 10 mms In the quasi-static tests the specimens were placed on the lower fixed circular platen The fixed platen consisted of holes around the centre to allow the entrapped air to escape during testing Figure 2 shows the experimental setup of the MTS machine for quasi-static tests The indenter was connected to the upper load cell which moved downwards to crush the specimens Fixed position of the specimens on the circular platen was maintained for all the tests Both indentation and compressive tests were conducted using the MTS machine at velocities of 005 mms 05 mms and 5 mms respectively The corresponding nominal strain rates were 10-3 10-2 and 10-1 s-1 respectively for the specimen with a thickness of 50 mm Compressive force 119865119888 was measured in the compressive tests The total force measured in the

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

3

indentation tests 119865119879 was the sum of the compressive force 119865119888 and tearing force 119865119905 Thus the tearing force could be calculated as 119865119905 = 119865119879 minus 119865119888

23 Dynamic Tests

Figure 3 Out-of-plane dynamic indentation tests conducted on the high speed INSTRON machine Out-of-plane dynamic tests were conducted on a high speed INSTRON (VHS8800) machine which has capacity to generate a maximum velocity of 10 ms Both indentation and compressive tests were conducted at a velocity of 5 ms Figure 3 shows the experimental setup of the INSTRON machine for dynamic indentation tests In the experiment the circular fixed platen was connected to the upper load cell The specimens were attached to the fixed upper platen by using rubber bands for the indentation tests and specimens were fasten to the indenter by double-sided tape in compressive tests The indenter was connected to the lower piston of the machine which moved upwards to apply the impact force to the specimens

3 Results and Discussions The force-displacement curves of three types of aluminium honeycombs subjected to indentation and compressive loads at velocities of 005 mms 05 mms 5 mms and 5 ms are shown in Figures 4-7 respectively It can be seen from Figures 4-7 that the plateau forces in the quasi-static tests (Figures 4-6) for all types of honeycomb specimens are generally constant While in the dynamic tests (5 ms Figure 7) the transient forces fluctuate significantly in the plateau region

The average plateau force was calculated by taking the average force within a displacement range of 3 - 38 mm The mean plateau stress was calculated as the ratio of average force to the cross-sectional area of the honeycomb specimen The mean plateau stresses of three different honeycomb materials at different velocities 005 mms 05 mms 5mms and 5ms are listed in Table 2 It has been observed that the mean plateau stress in both indentation and compressive tests increases with the increase in velocity However the tearing strength 119865119905 = 119865119879 minus 119865119888 did not show any trend with the change of the velocity The area under the force-displacement curve is the total energy absorbed by honeycombs The energy absorbed by honeycombs in compression 119864119888 is the area under the force-displacement curves recorded in compressive tests

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

4

(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

0

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kN

Distance mm

A1 B1 C1

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kN

Distance mm

A2 B2 C2

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

5

(a)

(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

0

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0 10 20 30 40 50 60

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A3 B3 C3

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A4 B4 C4

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

6

(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A5 B5 C5

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kN

Distance mm

A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A7 B7 C7

-10

0

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60

0 10 20 30 40 50

Load

kN

Distance mm

A8 B8 C8

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

8

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

9

C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

Indentation tests of aluminium honeycombs

A Ashab1 Y C Wong1 G Lu2 and D Ruan1 3 1Faculty of Engineering and Industrial Sciences Swinburne University of Technology Hawthorn VIC 3122 Australia 2School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore 639798 Email druanswineduau

Abstract Aluminium honeycomb is a type of cellular material which has high strength to weigh ratio and is a good energy absorber They are used as structural components in various engineering applications Comprehensive study has been conducted on the compressive behavior of aluminium honeycombs However the research of aluminium honeycombs subjected to other type of loading such as indentation is still limited In this paper quasi-static and dynamic indentation tests were conducted to study the deformation and energy absorption of three types of HEXCELLreg aluminium honeycombs with different cell sizes and cell wall thicknesses Quasi-static tests were conducted by using a universal MTS machine at velocities of 005 mms 05 mms and 5 mms respectively Dynamic tests were conducted by using a high speed INSTRON machine at a velocity of 5 ms Force-displacement curves were plotted in which the total energy absorbed was calculated The deformation of aluminium honeycombs in indentation tests includes the compression of honeycomb cells under the indenter and tearing of honeycomb cell walls along the indenter edges The energy dissipated in compression and tearing were calculated and discussed The effects of cell size cell wall thickness and loading velocity or strain rate on the plateau stress and energy absorption were analyzed

1 Introduction Aluminium honeycombs are lightweight and have good energy absorption capabilities They are widely used as core materials in various fields of engineering such as aerospace and automotive because of their extensive engineering properties Some of the applications of aluminium honeycombs are landing gear door and flaps of aircraft For example crushable aluminium honeycombs had been used in the Apollo 11 lading module The large plastic deformation in hexagonal honeycombs is the main energy absorption region It has been demonstrated that the plastic deformation and energy absorption characteristics of aluminium honeycombs depends on both the geometrical configuration and mechanical properties of cell wall materials [1 2] Cell size cell wall thickness and strain rate are important parameters that affect plateau stress as well as impact response of aluminium honeycombs Gibson and Ashby [1] pointed out that the deformation pattern and compressive strength varied with the direction of loads for example aluminium honeycombs strength is higher in the out-of plane direction compared with the two in-plane directions A schematic diagram of aluminum honeycomb structure is shown in Figure 1 The cell wall thickness t and 2t are known as single wall and double wall respectively The cell edge length is denoted as l while h is the thickness of honeycomb ______________________________ 3 To whom any correspondence should be addressed

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

Content from this work may be used under the terms of the Creative Commons Attribution 30 licence Any further distributionof this work must maintain attribution to the author(s) and the title of the work journal citation and DOI

Published under licence by IOP Publishing Ltd 1

Buckling folding stretching de-bonding and tearing are the major failure mechanisms of aluminium honeycombs Many researchers [3-6] studied aluminium honeycombs experimentally numerically and theoretically to characterize their crushing behaviour and failure mechanism under both quasi-static and dynamic compression Zhou and Mayer [7] conducted compressive and indentation punch tests on two types of aluminium honeycombs with different cell sizes (64 mm and 191 mm respectively) In compression the honeycomb with larger cell size was found to be strain rate dependent while the 3honeycomb with smaller cell size did not show evident strain rate sensitivity Quasi-static tearing strength of honeycomb was defined measured and calculated from the indentation punch tests Two types of honeycombs deformed differently However since no dynamic indentation punch test was conducted the strain rate sensitivity is still unknown

Figure 1 Schematic diagram of an aluminium honeycomb structure

In the present paper out-of-plane quasi-static and dynamic indentations and compressive tests have been conducted using MTS and high speed INSTRON machines to investigate tearing and compressive strengths Three types of aluminium honeycombs having different cell sizes and wall thicknesses have been used in the experiment For quasi-static tests velocities of 005 mms 05 mms and 5 mms were used and for dynamic tests a velocity of 5 ms was used The tearing and compressive strengths were calculated from the experimental results and the dependency of the dissipated energy on the loading speed was also discussed

2 Experiments 21 Specification of materials and specimens HEXCELLreg aluminium honeycombs with different cell sizes and wall thicknesses were used in the experiments The specific material used is aluminium alloy 5052 with an H39 temper The properties of three types of honeycombs are listed in Table 1 Each of the hexagonal honeycomb cell contain four single walls and two adjacent double walls of which all the cells are inter-connected to each other The thickness of the double walls is twice of the single wall thickness In compressive tests honeycomb specimens used were 90 mm times 90 mm In indentation tests honeycomb specimens used were 180 mm times 180 mm All honeycomb specimens were 50 mm in height

The dimension of the indenter used in the indentation tests was a 90 mm times 90 mm which covers at least 9 times 9 cells of all types of honeycombs studied This cross-section of the indenter used was to ensure almost uniform compression of honeycomb cells A circular plate with holes was used as fixed

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

2

platen where the honeycomb specimen was placed In order to avoid specimen dis-connected with the platen rubber bands double sided tape was used to fasten the specimen in the platen The holes in the circular plate are for the entrapped air to escape during testing Therefore in this experiment the effect of entrapped air could be ignored

Table 1 HEXCELLreg 5052 aluminium hexagonal honeycomb Name Material Cell

size D (mm)

Cell wall thickness t

(mm)

Nominal Density 120646 (kgm3)

Modulus (GPa)

Crush Strength (MPa)

No of cells

covered by

Indenter A 31-316-5052-001N 4763 00254 4966 052 090 19times19

B 42-38-5052-003N 9525 00762 6728 093 152 9times9

C 45-18-5052-001N 3175 00254 7209 103 179 28times28

22 Quasi-static tests

Figure 2 Out-of-plane quasi-static indentation tests conducted on the 50 kN MTS machine

Out-of-plane quasi-static tests were conducted on an MTS machine (Model LPS504) which had a load capacity of 50 kN that could reach a velocity of 10 mms In the quasi-static tests the specimens were placed on the lower fixed circular platen The fixed platen consisted of holes around the centre to allow the entrapped air to escape during testing Figure 2 shows the experimental setup of the MTS machine for quasi-static tests The indenter was connected to the upper load cell which moved downwards to crush the specimens Fixed position of the specimens on the circular platen was maintained for all the tests Both indentation and compressive tests were conducted using the MTS machine at velocities of 005 mms 05 mms and 5 mms respectively The corresponding nominal strain rates were 10-3 10-2 and 10-1 s-1 respectively for the specimen with a thickness of 50 mm Compressive force 119865119888 was measured in the compressive tests The total force measured in the

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

3

indentation tests 119865119879 was the sum of the compressive force 119865119888 and tearing force 119865119905 Thus the tearing force could be calculated as 119865119905 = 119865119879 minus 119865119888

23 Dynamic Tests

Figure 3 Out-of-plane dynamic indentation tests conducted on the high speed INSTRON machine Out-of-plane dynamic tests were conducted on a high speed INSTRON (VHS8800) machine which has capacity to generate a maximum velocity of 10 ms Both indentation and compressive tests were conducted at a velocity of 5 ms Figure 3 shows the experimental setup of the INSTRON machine for dynamic indentation tests In the experiment the circular fixed platen was connected to the upper load cell The specimens were attached to the fixed upper platen by using rubber bands for the indentation tests and specimens were fasten to the indenter by double-sided tape in compressive tests The indenter was connected to the lower piston of the machine which moved upwards to apply the impact force to the specimens

3 Results and Discussions The force-displacement curves of three types of aluminium honeycombs subjected to indentation and compressive loads at velocities of 005 mms 05 mms 5 mms and 5 ms are shown in Figures 4-7 respectively It can be seen from Figures 4-7 that the plateau forces in the quasi-static tests (Figures 4-6) for all types of honeycomb specimens are generally constant While in the dynamic tests (5 ms Figure 7) the transient forces fluctuate significantly in the plateau region

The average plateau force was calculated by taking the average force within a displacement range of 3 - 38 mm The mean plateau stress was calculated as the ratio of average force to the cross-sectional area of the honeycomb specimen The mean plateau stresses of three different honeycomb materials at different velocities 005 mms 05 mms 5mms and 5ms are listed in Table 2 It has been observed that the mean plateau stress in both indentation and compressive tests increases with the increase in velocity However the tearing strength 119865119905 = 119865119879 minus 119865119888 did not show any trend with the change of the velocity The area under the force-displacement curve is the total energy absorbed by honeycombs The energy absorbed by honeycombs in compression 119864119888 is the area under the force-displacement curves recorded in compressive tests

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

4

(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

0

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30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A1 B1 C1

0

10

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0 10 20 30 40 50

Load

kN

Distance mm

A2 B2 C2

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

5

(a)

(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

0

10

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30

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0 10 20 30 40 50 60

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kN

Distance mm

A3 B3 C3

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Distance mm

A4 B4 C4

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

6

(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A5 B5 C5

0

10

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0 10 20 30 40 50

Load

kN

Distance mm

A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A7 B7 C7

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A8 B8 C8

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

8

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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Buckling folding stretching de-bonding and tearing are the major failure mechanisms of aluminium honeycombs Many researchers [3-6] studied aluminium honeycombs experimentally numerically and theoretically to characterize their crushing behaviour and failure mechanism under both quasi-static and dynamic compression Zhou and Mayer [7] conducted compressive and indentation punch tests on two types of aluminium honeycombs with different cell sizes (64 mm and 191 mm respectively) In compression the honeycomb with larger cell size was found to be strain rate dependent while the 3honeycomb with smaller cell size did not show evident strain rate sensitivity Quasi-static tearing strength of honeycomb was defined measured and calculated from the indentation punch tests Two types of honeycombs deformed differently However since no dynamic indentation punch test was conducted the strain rate sensitivity is still unknown

Figure 1 Schematic diagram of an aluminium honeycomb structure

In the present paper out-of-plane quasi-static and dynamic indentations and compressive tests have been conducted using MTS and high speed INSTRON machines to investigate tearing and compressive strengths Three types of aluminium honeycombs having different cell sizes and wall thicknesses have been used in the experiment For quasi-static tests velocities of 005 mms 05 mms and 5 mms were used and for dynamic tests a velocity of 5 ms was used The tearing and compressive strengths were calculated from the experimental results and the dependency of the dissipated energy on the loading speed was also discussed

2 Experiments 21 Specification of materials and specimens HEXCELLreg aluminium honeycombs with different cell sizes and wall thicknesses were used in the experiments The specific material used is aluminium alloy 5052 with an H39 temper The properties of three types of honeycombs are listed in Table 1 Each of the hexagonal honeycomb cell contain four single walls and two adjacent double walls of which all the cells are inter-connected to each other The thickness of the double walls is twice of the single wall thickness In compressive tests honeycomb specimens used were 90 mm times 90 mm In indentation tests honeycomb specimens used were 180 mm times 180 mm All honeycomb specimens were 50 mm in height

The dimension of the indenter used in the indentation tests was a 90 mm times 90 mm which covers at least 9 times 9 cells of all types of honeycombs studied This cross-section of the indenter used was to ensure almost uniform compression of honeycomb cells A circular plate with holes was used as fixed

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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platen where the honeycomb specimen was placed In order to avoid specimen dis-connected with the platen rubber bands double sided tape was used to fasten the specimen in the platen The holes in the circular plate are for the entrapped air to escape during testing Therefore in this experiment the effect of entrapped air could be ignored

Table 1 HEXCELLreg 5052 aluminium hexagonal honeycomb Name Material Cell

size D (mm)

Cell wall thickness t

(mm)

Nominal Density 120646 (kgm3)

Modulus (GPa)

Crush Strength (MPa)

No of cells

covered by

Indenter A 31-316-5052-001N 4763 00254 4966 052 090 19times19

B 42-38-5052-003N 9525 00762 6728 093 152 9times9

C 45-18-5052-001N 3175 00254 7209 103 179 28times28

22 Quasi-static tests

Figure 2 Out-of-plane quasi-static indentation tests conducted on the 50 kN MTS machine

Out-of-plane quasi-static tests were conducted on an MTS machine (Model LPS504) which had a load capacity of 50 kN that could reach a velocity of 10 mms In the quasi-static tests the specimens were placed on the lower fixed circular platen The fixed platen consisted of holes around the centre to allow the entrapped air to escape during testing Figure 2 shows the experimental setup of the MTS machine for quasi-static tests The indenter was connected to the upper load cell which moved downwards to crush the specimens Fixed position of the specimens on the circular platen was maintained for all the tests Both indentation and compressive tests were conducted using the MTS machine at velocities of 005 mms 05 mms and 5 mms respectively The corresponding nominal strain rates were 10-3 10-2 and 10-1 s-1 respectively for the specimen with a thickness of 50 mm Compressive force 119865119888 was measured in the compressive tests The total force measured in the

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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indentation tests 119865119879 was the sum of the compressive force 119865119888 and tearing force 119865119905 Thus the tearing force could be calculated as 119865119905 = 119865119879 minus 119865119888

23 Dynamic Tests

Figure 3 Out-of-plane dynamic indentation tests conducted on the high speed INSTRON machine Out-of-plane dynamic tests were conducted on a high speed INSTRON (VHS8800) machine which has capacity to generate a maximum velocity of 10 ms Both indentation and compressive tests were conducted at a velocity of 5 ms Figure 3 shows the experimental setup of the INSTRON machine for dynamic indentation tests In the experiment the circular fixed platen was connected to the upper load cell The specimens were attached to the fixed upper platen by using rubber bands for the indentation tests and specimens were fasten to the indenter by double-sided tape in compressive tests The indenter was connected to the lower piston of the machine which moved upwards to apply the impact force to the specimens

3 Results and Discussions The force-displacement curves of three types of aluminium honeycombs subjected to indentation and compressive loads at velocities of 005 mms 05 mms 5 mms and 5 ms are shown in Figures 4-7 respectively It can be seen from Figures 4-7 that the plateau forces in the quasi-static tests (Figures 4-6) for all types of honeycomb specimens are generally constant While in the dynamic tests (5 ms Figure 7) the transient forces fluctuate significantly in the plateau region

The average plateau force was calculated by taking the average force within a displacement range of 3 - 38 mm The mean plateau stress was calculated as the ratio of average force to the cross-sectional area of the honeycomb specimen The mean plateau stresses of three different honeycomb materials at different velocities 005 mms 05 mms 5mms and 5ms are listed in Table 2 It has been observed that the mean plateau stress in both indentation and compressive tests increases with the increase in velocity However the tearing strength 119865119905 = 119865119879 minus 119865119888 did not show any trend with the change of the velocity The area under the force-displacement curve is the total energy absorbed by honeycombs The energy absorbed by honeycombs in compression 119864119888 is the area under the force-displacement curves recorded in compressive tests

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

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0 10 20 30 40 50

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Distance mm

A1 B1 C1

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Distance mm

A2 B2 C2

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

0

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40

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0 10 20 30 40 50 60

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A3 B3 C3

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Load

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Distance mm

A4 B4 C4

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

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kN

Distance mm

A5 B5 C5

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Load

kN

Distance mm

A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

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A7 B7 C7

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kN

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A8 B8 C8

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honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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platen where the honeycomb specimen was placed In order to avoid specimen dis-connected with the platen rubber bands double sided tape was used to fasten the specimen in the platen The holes in the circular plate are for the entrapped air to escape during testing Therefore in this experiment the effect of entrapped air could be ignored

Table 1 HEXCELLreg 5052 aluminium hexagonal honeycomb Name Material Cell

size D (mm)

Cell wall thickness t

(mm)

Nominal Density 120646 (kgm3)

Modulus (GPa)

Crush Strength (MPa)

No of cells

covered by

Indenter A 31-316-5052-001N 4763 00254 4966 052 090 19times19

B 42-38-5052-003N 9525 00762 6728 093 152 9times9

C 45-18-5052-001N 3175 00254 7209 103 179 28times28

22 Quasi-static tests

Figure 2 Out-of-plane quasi-static indentation tests conducted on the 50 kN MTS machine

Out-of-plane quasi-static tests were conducted on an MTS machine (Model LPS504) which had a load capacity of 50 kN that could reach a velocity of 10 mms In the quasi-static tests the specimens were placed on the lower fixed circular platen The fixed platen consisted of holes around the centre to allow the entrapped air to escape during testing Figure 2 shows the experimental setup of the MTS machine for quasi-static tests The indenter was connected to the upper load cell which moved downwards to crush the specimens Fixed position of the specimens on the circular platen was maintained for all the tests Both indentation and compressive tests were conducted using the MTS machine at velocities of 005 mms 05 mms and 5 mms respectively The corresponding nominal strain rates were 10-3 10-2 and 10-1 s-1 respectively for the specimen with a thickness of 50 mm Compressive force 119865119888 was measured in the compressive tests The total force measured in the

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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indentation tests 119865119879 was the sum of the compressive force 119865119888 and tearing force 119865119905 Thus the tearing force could be calculated as 119865119905 = 119865119879 minus 119865119888

23 Dynamic Tests

Figure 3 Out-of-plane dynamic indentation tests conducted on the high speed INSTRON machine Out-of-plane dynamic tests were conducted on a high speed INSTRON (VHS8800) machine which has capacity to generate a maximum velocity of 10 ms Both indentation and compressive tests were conducted at a velocity of 5 ms Figure 3 shows the experimental setup of the INSTRON machine for dynamic indentation tests In the experiment the circular fixed platen was connected to the upper load cell The specimens were attached to the fixed upper platen by using rubber bands for the indentation tests and specimens were fasten to the indenter by double-sided tape in compressive tests The indenter was connected to the lower piston of the machine which moved upwards to apply the impact force to the specimens

3 Results and Discussions The force-displacement curves of three types of aluminium honeycombs subjected to indentation and compressive loads at velocities of 005 mms 05 mms 5 mms and 5 ms are shown in Figures 4-7 respectively It can be seen from Figures 4-7 that the plateau forces in the quasi-static tests (Figures 4-6) for all types of honeycomb specimens are generally constant While in the dynamic tests (5 ms Figure 7) the transient forces fluctuate significantly in the plateau region

The average plateau force was calculated by taking the average force within a displacement range of 3 - 38 mm The mean plateau stress was calculated as the ratio of average force to the cross-sectional area of the honeycomb specimen The mean plateau stresses of three different honeycomb materials at different velocities 005 mms 05 mms 5mms and 5ms are listed in Table 2 It has been observed that the mean plateau stress in both indentation and compressive tests increases with the increase in velocity However the tearing strength 119865119905 = 119865119879 minus 119865119888 did not show any trend with the change of the velocity The area under the force-displacement curve is the total energy absorbed by honeycombs The energy absorbed by honeycombs in compression 119864119888 is the area under the force-displacement curves recorded in compressive tests

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A1 B1 C1

0

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0 10 20 30 40 50

Load

kN

Distance mm

A2 B2 C2

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

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0 10 20 30 40 50 60

Load

kN

Distance mm

A3 B3 C3

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Load

kN

Distance mm

A4 B4 C4

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A5 B5 C5

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Load

kN

Distance mm

A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A7 B7 C7

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50

60

0 10 20 30 40 50

Load

kN

Distance mm

A8 B8 C8

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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indentation tests 119865119879 was the sum of the compressive force 119865119888 and tearing force 119865119905 Thus the tearing force could be calculated as 119865119905 = 119865119879 minus 119865119888

23 Dynamic Tests

Figure 3 Out-of-plane dynamic indentation tests conducted on the high speed INSTRON machine Out-of-plane dynamic tests were conducted on a high speed INSTRON (VHS8800) machine which has capacity to generate a maximum velocity of 10 ms Both indentation and compressive tests were conducted at a velocity of 5 ms Figure 3 shows the experimental setup of the INSTRON machine for dynamic indentation tests In the experiment the circular fixed platen was connected to the upper load cell The specimens were attached to the fixed upper platen by using rubber bands for the indentation tests and specimens were fasten to the indenter by double-sided tape in compressive tests The indenter was connected to the lower piston of the machine which moved upwards to apply the impact force to the specimens

3 Results and Discussions The force-displacement curves of three types of aluminium honeycombs subjected to indentation and compressive loads at velocities of 005 mms 05 mms 5 mms and 5 ms are shown in Figures 4-7 respectively It can be seen from Figures 4-7 that the plateau forces in the quasi-static tests (Figures 4-6) for all types of honeycomb specimens are generally constant While in the dynamic tests (5 ms Figure 7) the transient forces fluctuate significantly in the plateau region

The average plateau force was calculated by taking the average force within a displacement range of 3 - 38 mm The mean plateau stress was calculated as the ratio of average force to the cross-sectional area of the honeycomb specimen The mean plateau stresses of three different honeycomb materials at different velocities 005 mms 05 mms 5mms and 5ms are listed in Table 2 It has been observed that the mean plateau stress in both indentation and compressive tests increases with the increase in velocity However the tearing strength 119865119905 = 119865119879 minus 119865119888 did not show any trend with the change of the velocity The area under the force-displacement curve is the total energy absorbed by honeycombs The energy absorbed by honeycombs in compression 119864119888 is the area under the force-displacement curves recorded in compressive tests

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

(a)

(b)

Figure 4 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 005 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

8

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

(a)

(b)

Figure 5 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading velocity of 05 mms in (a) indentation tests (b) compressive tests

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Distance mm

A3 B3 C3

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A4 B4 C4

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

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0 10 20 30 40 50

Load

kN

Distance mm

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A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

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10

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kN

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A7 B7 C7

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Distance mm

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D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

8

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

(a)

(b)

Figure 6 Quasi-static force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 mms in (a) indentation tests (b) compressive tests

0

10

20

30

40

50

0 10 20 30 40 50

Load

kN

Distance mm

A5 B5 C5

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Load

kN

Distance mm

A6 B6 C6

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

7

(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

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0

10

20

30

40

50

60

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Load

kN

Distance mm

A7 B7 C7

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Load

kN

Distance mm

A8 B8 C8

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

8

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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(a)

(b) Figure 7 Dynamic force-displacement curves of three types of aluminium honeycombs at a loading

velocity of 5 ms in (a) indentation tests (b) compressive tests

The total energy absorbed by honeycombs in indentation 119864119879 is the area under the force-displacement curves recorded in indentation tests and listed in Table 3 Since both compression of

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A7 B7 C7

-10

0

10

20

30

40

50

60

0 10 20 30 40 50

Load

kN

Distance mm

A8 B8 C8

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

honeycomb cells and tearing along the 4 edges of honeycomb specimen occurred simultaneously in the indentation of honeycombs the total energy dissipated in tearing 119864119905 is calculated by the difference of 119864119879 and 119864119888

The percentages of compressive energy 119864119888 and tearing energy 119864119905 at different strain rates are listed in the Table 3 For honeycombs material 31-316-5052-001N (A1 A3 A5 A7) the percentage of compression and tearing energies varied in the range of 83 - 87 and 13 - 17 respectively For the honeycomb material 45-18-5052-001N (B1 B3 B5 B7) the percentages for compression energy and tearing energies were similar to those for honeycombs material 31-316-5052-001N However for honeycombs material 42-38-5052-003N the percentages of compression and tearing energies varied in the range of 70 - 74 and 26 - 30 respectively ie the tearing energy was higher than that of the other two types honeycomb materials This is mainly due to the thicker cell walls of honeycomb material (42-38-5052-003N) compared with the other two types of honeycomb materials However the tearing energy 119864119905 = 119864119879 minus 119864119888 did not change significantly with loading velocity

Table 2 Summary of experimental results

Test no

Material Test type 119957119949 Velocity (ms)

Mean plateau

stress 120648119953119949lowast (MPa)

Total Dissipated

energy (J)

A1 31-316-5052-001N Indentation 000924 5times10-5 107 304

A2 31-316-5052-001N Compression 089 252

A3 31-316-5052-001N Indentation 000924 5times10-4 108 305

A4 31-316-5052-001N Compression 093 264

A5 31-316-5052-001N Indentation 000924 5times10-3 112 323

A6 31-316-5052-001N Compression 089 268

A7 31-316-5052-001N Indentation 000924 5 12 338

A8 31-316-5052-001N Compression 104 295

B1 42-38-5052-003N Indentation 00139 5times10-5 195 546

B2 42-38-5052-003N Compression 135 382

B3 42-38-5052-003N Indentation 00139 5times10-4 209 586

B4 42-38-5052-003N Compression 144 409

B5 42-38-5052-003N Indentation 00139 5times10-3 201 598

B6 42-38-5052-003N Compression 153 444

B7 42-38-5052-003N Indentation 00139 5 227 643

B8 42-38-5052-003N Compression 174 460

C1 45-18-5052-001N Indentation 00139 5times10-5 218 616

C2 45-18-5052-001N Compression 184 522

C3 45-18-5052-001N Indentation 00139 5times10-4 219 619

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

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C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

C4 45-18-5052-001N Compression 176 526

C5 45-18-5052-001N Indentation 00139 5times10-3 228 661

C6 45-18-5052-001N Compression 198 553

C7 45-18-5052-001N Indentation 00139 5 242 683

C8 45-18-5052-001N Compression 203 576

Table 3 Effect of strain rate on the dissipated energy

Test no

Strain rate (s-1)

Compression energy

Tearing energy

A1 10minus3 83 17

A3 10minus2 86 14

A5 10minus1 83 17

A7 100 87 13

B1 10minus3 70 30

B3 10minus2 70 30

B5 10minus1 74 26

B7 100 71 29

C1 10minus3 84 16

C3 10minus2 84 16

C5 10minus1 83 17

C7 100 84 16

4 Conclusions The out-of-plane indentation and compression behaviours of three types of aluminium honeycombs were investigated experimentally by using an MTS machine and a high speed INSTRON machine In both quasi-static and dynamic tests constant velocity was achieved in all tests Force-displacement curves were recorded in all tests and presented Mean plateau stress and energy absorbed in compression and indentation of honeycombs were calculated Results indicated that both mean plateau stress and total energy absorbed in compression and indentation increased with the density of honeycombs and loading velocity or strain rate The tearing strength and tearing energies increased with the cell wall thickness of honeycomb no trend was observed with the change of loading velocity or strain rate in this study Further detailed study will be carried out in the near future with a focus on the strain rate effect on tearing strength and energy

Acknowledgements The authors are grateful to Swinburne University of Technology for the financial support through a postgraduate scholarship the Australia Research Council for the financial support through a Discovery grant and Dr Shanqing Xu for his help in the experiments

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

10

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11

References [1] Gibson L J and Ashby M F 1997 Cellular solids structure and properties 2nd ed (Cambridge

Cambridge University Press) [2] Yamashita M and Gotoh M 2005 Int J of Impact Eng 32 618 [3] Zhang J and Ashby M F 1992 Int J of Mech Sci 34 475 [4] Xu S Beynon J H Ruan D and Lu G 2012 Compos Struct 94 2326 [5] Masters I G and Evans K E 1996 Compos Struct 35 403 [6] Wierzbicki T 1983 Int J of Impact Eng 1 157 [7] Zhou Q and Mayer R R 2002 J Eng Mater-T ASME 124 412

D2FAM 2013 IOP PublishingJournal of Physics Conference Series 451 (2013) 012003 doi1010881742-65964511012003

11