Auxetics: From Foams to Composites and Beyond

Fabrizio Scarpa, f.scarpa@bristol.ac.uk

www.bris.ac.uk/composites

Contents

Introduction

Foams

Honeycombs and truss-cores

Composites

Nano-auxetics

Conclusions

Acknowledgements

A. Bezazi, M. Bianchi, P. Pastorino, M. Ruzzene, C. Lira, C. D. L. Remillat, L. G. Ciffo, M. R. Hassan, T. L. Lew, A. Spadoni, K.

Saito, C. W. Smith, W. H. Bullough, H. Abramovitch, M. Burgard, M. Hoffmeister, M. Celuch, K. E. Evans, F. C. Smith, R. Neville, C. Coconnier, S. Jacobs, J. Martin, M. Bruckner, A. Alderson, K.

Alderson, P. Innocenti, A. Lorato, Y. H. Tai,J. Yates, K. Worden, A. B. Spencer and G. Tomlinson

Special thanks for their contribution to:Special thanks for their contribution to:

Introduction• From the Greek auxetos: “that can expand”• Indicates Negative Poisson’s ratio (NPR) materials

5.01 Homogeneous, isotropic solid

122211 EE Special orthotropic solid

3

22

1613Et

FR

Central deflection of a clamped circular plate

32211

HHardness – increase with NPR – the material wraps around the indenter

Synclastic curvature – easy manufacturing of dome-shaped structures

(University of Bolton, 2008)

Introduction

Fibril Hinging(microporous UHMWPE and PFTE - GoreTex©)

(courtesy of Azon.com)A. Alderson, K. E. Evans, J. Mater. Sci. 1997, 32, 2797.

Introduction

Rotating rectangles

J.N. Grima et al., Adv. Mater., 12 (2000)1912; A. Alderson et al., International Patent No. PCT/GB98/03281 (1998).

Used to prototype “smart” filters for chemical processes.Possible explanation of auxetic behaviour in some forms of a-crystobalite

(Courtesy of Professor Joseph Grima, http://home.um.edu.mt/auxetic/properties.htm)

Introduction

x

RL

ry

t

(D. Prall and R. Lakes, Int. J. Mech. Sci., 39, 305-314, 1996)

•Rotations of the nodes induce bending of the ligaments•Isotropic in-plane properties ( = -1)

LbrtrLo 30

LR

Foams

Strain dependent tensile PoissonStrain dependent tensile Poisson’’s ratios ratio

(Scarpa, et al. Phys. Stat. Solidi B, 242(3) 2005, 681-694 )

Foams

1. Multiaxial compression

ConventionalPU based foam

4. Relaxation of

the sample2. Annealing

3. Cooling

FoamsConventional PU foam

Non-auxetic iso-density

Auxetic ( = -0.26)

Foams

Compression is the mostsignificant manufacturing parameter forauxetic foams.

(M. Bianchi, F Scarpa, C W Smith. J. Mat. Sci. 43(17), 5851)

Foams

r = 0.95

0

10

20

30

40

50

60

70

80

0 25000 50000 75000 100000

Number of cycles N

Ene

rgy

U [m

j/cm

3]

Conventional

Iso density

Auxetic

Smart auxetic foams

(F. Scarpa, W. A. Bullough and P. Lumley, IMechE Proc. Part C, 216, 2004)

Doping auxetic foams with magnetorheological fluids can provide a tuned acoustic absorber with shift peak varying with the intensity of an external magnet

Shape Memory effect

Auxetic Sample

ReturnedSample

Shape Memory effect

(a) (b)

(c) (d)

SEM images of (a)conventional, (b )1st auxetic, (c)returned from auxetic and (d) 2nd auxetic open-cell PU based foam

(Bianchi M., Scarpa F, Smith C. W., 2010. Acta Mater. 58(3), 858)

Foams – New manufacturing process

New manufacturing process for Auxetic foams

(Bianchi M., Scarpa F. Banse M. Smith C. W., 2011. Acta Mater. 59(2), 686)

Foams – Vibration transmissibility

50 100 150 2000

1

2

3

4

5

6

7

8

9

ω [Hz]

|XR

|

AuxeticConventional

Centre-symmetric honeycombs

sin2sincoscos2224

c

Flexible topology to enhance the mechanical and thermal conductivity performance

Centre-symmetric honeycombsINCONEL 617 coreConduction – radiation problem

Point A

Point BTime 0 s – uniform 273 KTime 20 s – 1400 K at upper face

In upper surfaces, temperatures are lower for auxetic configurations

NPR configurations

PPR configurations

(Innocenti P., Scarpa F, 2009. J. Comp. Mat. 43(21), 2419)

Centre-symmetric honeycombs

Shape memory alloy honeycombsShape memory alloy honeycombs

Centre-symmetric honeycombs

Nonlinear in-plane properties – SMA honeycombs

(Hassan MR, Scarpa F, Mohamed NA. Journal of Intelligent Material Systems and Structures 2009 20: 897-905 )

Zero honeycombs (SILICOMB)

(Lira C, Scarpa F, Tai Y H, Yates J R, 2011. Comp. Sci. Tech. In press)(Lira C, Scarpa F, M. Olszewska and M. Celuch, 2009. Phys Status Solidi B 246, 2055)

Gradient honeycombs

(Lira C, Scarpa F., 2010. Comp. Sci. Tech. 70(6), 930)(Lira C., Scarpa F. Rajasekaran R., 2011. J. Int. Mat. Syst. Struct. In press)

Kirigami/Origami honeycombs

(Saito K,. Neville R. Scapa F., ICCS16 Porto, 28-30 June 2011)(Saito K., Agnese F., Scarpa F, 2011. J. Int. Mat. Syst. Struct. In press)

Chiral structures

(Scarpa F., 2010. Comp. Sci. Tech. 70. CHISMACOMB Special Issue)

•Developed using RTM techniques for maritime sandwich applications•Core with polyester/glass fibre•Superior specific compressive and shear strength compared to analogous cores in marine constructions •Possibility of embedding sensors (PZT, MFCs) for SHM or other monitoring applications•Flat or curved panels easily manufactured with no in-plane buckling stresses•Developed and commercialised by CHISMATECH (Catania, I)

Chiral structures

(Spadoni A,. Ruzzene M., Scarpa F, 2006. J. Int. Mat. Syst. Struct. 17(11), 941)

Applied torque

Truss-core beam

1150 Hz1120 Hz

Deformed configurations for excitation at resonant frequencies:Numerical

Experimental

Localized deformationsLocalized deformations

Chiral structures

(Bornengo D., Scarpa F., Remillat C D L., 2005. IMechE Part G: J. Aerospace Eng. 219,185)(Martin J. et al, 2008. Physica Status Solidi B 245(3), 570)

Eppler420 for racecar wing design

Deflection vs Velocity at 15º

0

0.5

1

1.5

2

2.5

0 10 20 30 40 50 60 70Velocity (m/s)

Verti

cal D

efle

ctio

n (m

m) Experimental

FEA InviscidFEA Viscous

Chiral wingbox provides continuous camber variation with a stiff bending

airfoil

Deployable SMA antenna demonstrator

ESA Astr

ium ULR Ø

3mSSBR Ø

6m

Foldable Tips

Ø6m

Thin Shell Pan

el Ø

6mSMART Ø

6mAstr

omesh Ø

9mAstr

omesh Ø

12m

Chiral D

eployab

le Ø3m

Chiral D

eployab

le Ø6m

Chiral D

eployab

le Ø9m

Chiral D

eploy

able Ø

12m

Packed to Deployed Area RatioWeight to Area Ratio

Auxetic composite laminates

Static load/displacement curves

= -0.156

= 0.086

Carbon

-0.9

-0.6

-0.3

0

0.3

0.6

0 20 40 60 80 100

[Degrees]

13

ST 8ST 10ST 12ST 14ST 15ST 16ST 17ST 18ST 19ST 3

Name0 Stacking sequence Name Stacking sequence Name Stacking sequence

ST 1 [±

θ2

]s ST 11 [±

33 /±

θ

]s ST 21 [±

10 /±

θ

]s

ST 2 [02 /±

θ

]s ST 12 [±

35 /±

θ

]s ST 22 [±

15 /±

θ

]s

ST 3 [902 /±

θ

]s ST 13 [±

37 /±

θ

]s ST 23 [±16 /±

θ

]s

ST 4 [-

θ/+ θ/-

θ/+θ/]s ST 14 [±

40 /±

θ

]s ST 24 [±

17 /±

θ

]s

ST 5 [±

θ/ 02

]s ST 15 [±

45 /±

θ

]s ST 25 [±

18 /±

θ

]s

ST 6 [±

θ/902

]s ST 16 [±

50 /±

θ

]s ST 26 [±

19 /±

θ

]s

ST 7 [±

20 /±

θ

]s ST 17 [±

60 /±

θ

]s ST 27 [±

21 /±

θ

]s

ST 8 [±

25 /±

θ

]s ST 18 [±

70 /±

θ

]s ST 28 [±

22 /±

θ

]s

ST 9 [±

27 /±

θ

]s ST 19 [±

80 /±

θ

]s ST 29 [±

23 /±

θ

]s

ST 10 [±

30 /±

θ

]s ST 20 [±

5 /±

θ

]s ST 30 [±24 /±

θ

]s

(K Anderson, V R Simkins, V L Coenen, P J Davies, A Alderson, K Evans. Phys. Stat Solidi B, 242(3), 509 (2005) )

(E H Harkati, A Bezazi, F Scarpa, K Alderson, A Alderson. Phys. Stat Solidi B, 244(3), 883 (2007) )

Auxetic composite laminates

(Bezazi A., Boukharouba W., Scarpa F, 2009. Physica Status Solid B 246(9), 2102)

3-point bending (T300-914 prepreg)

Auxetic composite laminates

(Bezazi A., Boukharouba W., Scarpa F, 2009. Physica Status Solid B 246(9), 2102)

3-point bending (T300-914 prepreg)

Nano-auxetics in carbon structures

Weakening of C-C bonds strength → NPR in SWCNTs

(Jindal P., Jindal VK, 2006. J. Comp. Theor. Nanosci. 3(1), 148)

NPR effect when bond angle variation dominant deformation mechanism modification of force constants and bond length equilibrium

(Yao, YT, Alderson A, Alderson K., 2007. Paper presented at Auxetics 2007 @ Malta)

Evidence of in-plane NPR in buckypapers when mixing SWCNTs and MWCNTs

(Hall, LJ et al, 2008. Science, 320, 504)

Other possible mechanisms?

Nano-auxetics in carbon structures

Missing rib model (MRM) to explain NPR in open cell foams

Vacancy defects induced by electronic or ion irradiation

(Telling, R. H. et al, 2003. Nature Mat. 2, 333)

(Ajayan, PM, Ravikumar, V, Charlier, JC, 1998. Phys. Rev. Lett. 81, 1437)

(Mielke, SL, et al, 2004. Chem. Phys. Lett. 390, 413)

(Sammalkorpi M et al. 2004. Phys. Rev. B 70, 245416)

Uniaxial mechanical properties depending on % of vacant atoms

(C. W. Smith, J. N. Grima and K E Evans, 2000. Acta Mater. 48, 4349)

CNT and graphene mechanical properties

(F Scarpa and S Adhikari, 2008. J. Phys. D: App. Phys., 41, 085306)(Scarpa F., Adhikari S., Phani A S, 2009. Nanotechnology 20 065709)(Scarpa, FL, L. Boldrin, Peng, H-X, Remillat, CDL & Adhikari, S., 2010. Applied Physics Letters, 97, 151903)(R. Chowdhury, Adhikari, S, CY Wang & Scarpa, FL., 2010 Comp. Mat. Sci., 48, 730)(E.I. Saavedra Flores, Adhikari, S, Friswell, MI & Scarpa, FL, 2011. Comp.Mat. Sci., 50, 1083)(Scarpa, FL, J. W. Narojczyk & K. W. Wojciechowski., 2011., Physica Status Solidi B, 1, 82(Chowdhury R, Adhikari S, Rees P., Wilks S. P., Scarpa F., 2010. Phys. Rev. B 83, 045401)

Nano-auxetics in carbon structures

•FE nonlinear tensile loading simulations – applied strain 1.e-3•Random generation for vacancies•Elements attached to vacant atoms desactivated (ekill utility)•Combinations of SWCNT aspect ratio, radius and % of vacant atoms considered•12800 MC simulations

(F Scarpa, S Adhikari, C Y Wang 2009. J. Phys. D: App. Phys., 42(14), 142002)

Nano-auxetics in carbon structures

Mean Young’s modulus ratio and standard deviation Young’s modulus ratio for armchair (n,n). ●

= 2 % NRV; ■

= 1.5 % NRV; ▲= 1 % NRV; ◊

= 0.5 % NRV

(F Scarpa, S Adhikari, C Y Wang 2009. J. Phys. D: App. Phys., 42(14), 142002)

Nano-auxetics in carbon structures

Probability density functions for nrz in (n,n) tubes (R = 0.426 nm, AR=5)

Distribution of the standard deviations for (n,n) configurations (pristine nrz

between 0.29 and 0.16)

(F Scarpa, S Adhikari, C Y Wang 2009. J. Phys. D: App. Phys., 42(14), 142002)

Nano-auxetics in carbon structures

(6,0) rz = -0.41

Evidence on NPR in defective Evidence on NPR in defective CNTsCNTs found in NIfound in NI--CNT systemsCNT systems

(F Scarpa, S Adhikari, C Y Wang 2009. J. Phys. D: App. Phys., 42(14), 142002)

(Smolyanitsky A, Twari V K, 2011. Nanotechnology 22 085703)

Nano-auxetics in carbon structures

(Ma Y et al, 2010. App. Phys. Lett. 97 061909)

Nano-auxetics in carbon structures

(Chen L et al, 2009. App. Phys. Lett. 94 253111)

Conclusions

Auxetics and NPR can be engineered at different scales

Use of auxetic materials and structures needs lateral thinking

multidisciplinary research

There is scope for R&D activities at different TRLs – from blue sky to manufacturing of commercial prototypes

Conclusions

Thank you for Thank you for your attention!your attention!