AMC: high wear (particles seem not to reduce wear), high friction (with high noise) TISICS: fibres reduce wear from Ti to Ti-MMC, but then high wear on steel ball lower wear on both after polishing (SiC-fibres no more abrasive) low in vacuum and in CO2 when sliding along fibres

high friction (with noise) in all environments

Testing Earth – Results: Tensile Testing

SCC Test CTE Measurement

Goal: The main objective of the presented study was to select the most promising metallic based composites (MMC) which have a high specific stiffness (> 34 x106 m2/s2 ) to be used on planetary spacecraft such as for Mars surface missions.

Aerospace & Advanced Composites GmbH – AAC GmbH 2700 Wiener Neustadt, Austria, Viktor-Kaplan-Straße 2, T +43 (0) 2622 90550-500, F +43 (0) 2622 90550-99, grazyna.mozdzen@aac-research.at, www.aac-research.at

NOVEL  HIGH  SPECIFIC  STIFFNESS  MATERIALS  FOR  SPACE  APPLICATIONS  

G. Mozdzen1, M. Scheerer1, V. Liedtke1, A. Merstallinger1 , A. Norman2 , E. Neubauer3 , H.G. Wulz4

(1) Aerospace & Advanced Composites GmbH, Viktor Kaplan Strasse 2, 2700 Wiener Neustadt, Austria,Email: Grazyna.Mozdzen@aac-research.at (2) ESA (ESTEC), 2200 AG Noordwijk, The Netherlands, 3) RHP-Technology GmbH, 2444 Seibersdorf, Austria, (4) RTBV GmbH, 1230 Wien, Austria

AluCf: highest spec. stiffness, highest anisotropy, spec. strength below the expectation Ti64-TiB2: sufficient spec. stiffness, low anisotropy, low spec. strength, very low A value, AMC: sufficient spec. stiffness, low anisotropy, medium spec. strength, TiSiC: sufficient spec. stiffness, high spec. strength (L), anisotropy- better then AluCf, highest A value

Introduction: Newly developed materials with significantly improved levels of specific stiffness are aimed to reduce the mass of the structure of the entry modules by a large percentage whilst maintaining the performance. This could also allow some additional room to be gained within the body of the entry capsule, or lander / rover. Furthermore, by carefully selecting high specific stiffness materials, it should be possible to better tune the other material properties such as coefficient of thermal expansion (CTE), thermal conductivity or strength toward specific values.

References:

[1] J.T.Blucher, U.Narusawa, M.Katsumata, A.Nemeth - Continuous manufacturing of fiber-reinforced metal matrix composite wires – Technology and Product Characteristics Composites PART A 32(2001) 1759-1766

[2] J.D. Forest and J.L. Christian, Development and Application of Aluminium-Boron Composite Material. Journal of Aircraft Vol 7, Nr 2, March-April 1970

[3] Suraj Rawal, Metal Matrix Composites for Space Applications, JOM 53 (4) (2001), pp 14-17 [4] ESA 13th Symposium on Advanced Space Technologies in Robotics and Automation, ASTRA 2015, 11-13 May, ESA/ESTEC, Noordwijk, the Netherlands,

http://www.congrexprojects.com/2015-events/15a07/proceedings

Acknowledgment: The study presented has been carried out in the project founded by ESA in the frame of ESA Basic Technology Research Programme (TRP)

AMC: high wear (particles seem not to reduce wear), high friction (with high noise) TISICS: fibres reduce wear from Ti to Ti-MMC, but then high wear on steel ball lower wear on both after polishing (SiC-fibres no more abrasive) low in vacuum and in CO2 when sliding along fibres

high friction (with noise) in all environments

Ti64-TiB2: sufficient spec. stiffness, low anisotropy, low spec. strength, very low A value, Ti64-TiB2: sufficient spec. stiffness, low anisotropy, low spec. strength, very low A value, Ti64-TiB2: sufficient spec. stiffness, low anisotropy, low spec. strength, very low A value,

Testing Mars – Results: After exposures, no visible degradation of the samples had been observed

Tensile Testing

No statistical relevant degradation of the mechanical properties – specific young´s modulus, specific ultimate strength or total fracture strain due to the different thermal treatments; thermal cycling in vacuum, thermal cycling under martial environment or cryogenic immersion in LN2 – has been observed

Fatigue

Wear

Materials Selected for Testing Earth: Al Matrix Materials 1. Al-MMCp - AMC 640xa ( AA6061 + 40vol% SiC) 2. Al-MMCf (Al 99,85 + 60vol% C/M40 fibres) Ti Matrix Materials 3. Ti-MMCp (Ti6Al4V + 30-35vol% TiB2) 4. Ti-MMCf (Ti3Al2.5V + 33-35vol% SiC fibres) Reference Material: Ti6Al4V – ELI / grade 5.

Materials Selected for Testing Mars - based on the results obtained in test campaign Earth and material maturity 1.  Al-MMCp - AMC 640xa ( AA6061 + 40vol% SiC), 2.  TiMMCf (Ti3Al2.5V + 33-35vol% SiC fibres)

Conclusions: The study performed enabled to identify a high potential of an Al-alloy reinforced by SiC particles and a Ti-alloy reinforced by SiC fibres for space applications. These materials provide besides a high specific stiffness, also adequately high mechanical and physical properties. The decisive selection factor was finally the maturity of the candidates both of which are currently in production. Hence these materials can be considered as a replacement for the metallic parts on future Mars rovers, e.g. locomotion system, robotic arm and mast [4].

The materials have been evaluated to establish their performance in both Earth and Martian environments. In this connection a wide ranging review which included more than 150 candidates followed by a trade-off study considering the different technical properties, manufacturing and economic issues as well as environmental impact have been carried out [1,2,3].

Testing Earth: Incoming inspection (Microstructure, Hardness, Ultrasonic) Tensile Testing at RT [L, LT, 45°], - 100°C, + 100°C [L] SCC acc. to ECSS-Q-70-37C, Galvanic Corrosion, CTE; [-150;- +300]°C

TiSiC exhibits the best performance of all three composites tested . AluCf shows severe corrosion of Al-matrix. Ti64-TiB2 – too brittle for testing

AluCf exhibits the lowest CTE from all materials tested. It is followed by TiSiC, Ti64-TiB2, Ti64 and AMC materials.

Testing Mars: Incoming Inspection (Microstructure,Ultrasonic) Exposures; Thermal Cycling under Vacuum; [-120; +125] °C, 100 cycles Thermal Cycling under 6 mbar CO2; [-120; +40] °C, 100 cycles Cryo-Immersion into liquid nitrogen for 8 days duration Tensile Testing, Fatigue, Wear , Damping-Vibration

AMC TiSiCEL/ρ  as  received 50.27 49.94EL/ρ  cryo  immersion 46.32 52.90EL/ρ  vacuum  cycled 49.87 51.17EL/ρ  CO2  cycled 48.20 48.72

0

10

20

30

40

50

60

70

E/ρ

[GPa

/(g/

cm³)]

AMC TiSiCRm/ρ  as  received 180.58 382.38Rm/ρ  cryo  immersion 184.96 374.62Rm/ρ  vacuum  cycled 182.74 376.59Rm/ρ  CO2  cycled 166.22 383.40

0

50

100

150

200

250

300

350

400

450

Rm/ρ

[MPa/(g/cm

³)]

AMC TiSiCA  as  received 1.82 1.17A  cryo  immersion 2.04 1.10A  vacuum  cycled 1.82 0.98A  CO2  cycled 2.51 0.96

0.0

0.5

1.0

1.5

2.0

2.5

3.0

A  [%

]

The specific S-N curve for TiSiC shows higher specific fatigue levels in L-direction compared to AMC at the same cycles to failure, which is expected as the specific static strength of TiSiC is more than a factor of 2 higher

The slope of the specific S-N curve is higher for TiSiC materials indicating a higher sensitivity to fatigue compared to AMC.

PoD and Bush tests (against hard steel, uncoated, no lubrication) in air, vacuum and CO2 CO2

Vac.

AMC

Ti64-TiB2

TiSiC

Alu-Cf

Total strain at fracture

0

50

100

150

200

250

300

350

400

1000 10000 100000

stress  /  den

sity  [M

Pa/g/cm³]

cycles  to  failure

TiSiCAMC