The response of a quasi-isotropic laminate of metal matrix composite, SCS-6/Ti-15-3 in a thermomechanical fatigue (TMF) environment was investigated. To achieve this, three sets of fatigue tests were conducted: 1) in-phase TMF (IP-TMF), 2) out-of-phase TMF (OP-TMF), and 3) isothermal fatigue (IF). The fatigue response was dependent on the test condition and the maximum stress level during cycling. The IF, IP-TMF, and OP-TMF conditions yielded shortest fatigue life at higher, intermediate and lower stress levels, respectively. Examination of the failure mode through the variation of strain or modulus during cycling, and post-mortem microscopic evaluation revealed that it was dependent on the fatigue condition and applied stress level. Higher stresses, mostly with IP-TMF and IF conditions, produced a primarily fiber dominated failure. Lower stresses, mostly with the OP-TMF condition, produced a matrix dominated failure. Also, an empirical model based on the observed damage mechanisms was developed to represent the fatigue lives for the three conditions examined here.

Issue Section:
Technical Papers
Topics:
Fatigue, Metal matrix composites, Thermomechanics, Stress, Failure, Damage, Failure mechanisms, Fatigue life, Fatigue testing, Fibers, Laminates
1.
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2.
Castelli, M. G., Ellis, J. R., and Bartolotta, P. A., “Thermomechanical Testing Techniques for High Temperature Composites: TMF Behavior of SiC (SCS6) Ti-15–3,” NASA Technical Memorandum 103171, 1990.
3.
Mall
 
S.
, and
Ermer
 
P. G.
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Thermal Fatigue Behavior of a Unidirectional SCS-6/Ti-15–3 Metal Matrix Composite
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25
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1668
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86
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4.
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T. P.
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R. A.
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Isothermal and Nonisothermal Fatigue Behavior of a Metal Matrix Composite
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686
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5.
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6.
Mall
 
S.
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Schubbe
 
J. J.
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Thermomechanical Fatigue Behavior of a Cross-Ply SCS-6/Ti-15–3 Metal Matrix Composite
,”
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7.
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B.
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Characterization of Fatigue Behavior in Cross Ply Laminate of SCS-6/Ti-15–3 Metal Matrix Composite at Elevated Temperature
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8.
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9.
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10.
Russ, S. M., Nicholas, T., Bates, M., and Mall, S., “Thermomechanical Fatigue of SCS-6/Ti-24Al-11Nb Metal Matrix Composite,” Proc. of the ASME Symposium, Failure Mechanisms in High Temperature Composite Materials, AD-Vol. 22/AMD-Vol. 122, Dec. 1991, pp. 37–43.
11.
Mall
 
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D. G.
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S. M.
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Thermomechanical Fatigue Behavior of a Cross-ply SCS-6/β21-S Metal Matrix Composite
,”,
Constitutive Behavior of High-Temperature Composites
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12.
Johnson, W. S., Lubowinski, S. J., and Highsmith, A. L., “Mechanical Characterization of SCS-6/Ti-15-3 Metal Matrix Composites at Room Temperature,” Thermal and Mechanical Behavior of Ceramic and Metal Matrix Composites, ASTM STP 1080, 1990, pp. 193–218.
13.
Hart, K., “Behavior of a Quasi-Isotropic Ply Metal Matrix Composite Under Thermomechanical and Isothermal Fatigue Loading,” MS thesis, AFIT/GAE/ENY/92D-05, School of Engineering, Air Force Institute of Technology (AU), Wright-Patterson AFB OH, Dec. 1992.
14.
Majumdar
 
B. S.
, and
Newaz
 
G. M.
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Inelastic Deformation in Metal Matrix Composites: Plasticity and Damage Mechanisms
,”
Philosophical Magazine
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2
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15.
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D. D.
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Mall
 
S.
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Micromechanical Relations for Fiber-Reinforced Composites Using the Free Transverse Shear Approach
,”
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16.
Bates, Mark A., “Thermo-Mechanical Fatigue of a Fiber Reinforced Titanium Aluminide Composite,” MS thesis, AFIT/GAE/ENY-91S-1, School of Engineering, Air Force Institute of Technology (AU), Wright-Patterson AFB OH, Mar. 1991.
17.
Hopkins, D. A., and Chamis, C. C, “A Unique Set of Micromechanics Equations for High Temperature Metal Matrix Composites,” NASA TM-87154, Nov. 1985.
18.
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19.
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