Thermomechanical Fatigue Behavior of a Quasi-lsotropic SCS-6/Ti-15-3 Metal Matrix Composite

1995 ◽  
Vol 117 (1) ◽  
pp. 109-117 ◽  
Author(s):  
K. A. Hart ◽  
S. Mall
Keyword(s):  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Stress Level ◽  
Metal Matrix ◽  
Maximum Stress ◽  
Fatigue Behavior ◽  
Thermomechanical Fatigue ◽  
Fatigue Tests ◽  
Microscopic Evaluation ◽  
Observed Damage

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.

Fatigue Behavior of a Cross-Ply Metal Matrix Composite at Elevated Temperature Under the Strain Controlled Mode

1997 ◽  
Vol 119 (4) ◽  
pp. 422-428
Author(s):  
B. P. Sanders ◽  
S. Mall ◽  
L. B. Dennis
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Metal Matrix Composite ◽  
Failure Mode ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Fatigue Behavior ◽  
Matrix Cracking ◽  
Maximum Strain ◽  
Damage Mechanisms

A study was conducted to investigate the fatigue behavior of a cross-ply metal matrix composite subjected to fully-reversed, strain-controlled fatigue cycling at elevated temperature. The stress-strain response, maximum and minimum stresses, and modulus during cycling were analyzed to characterize the macro-mechanical behavior. Additionally, microscopy and fractography were conducted to identify damage mechanisms. Damage always initiated in the 90 deg plies, but the governing factor in the fatigue life was damage in the 0 deg plies. The dominant failure mode was fracturing of fibers in the 0 deg plies when the maximum strain was greater than 0.55 percent, but the dominant failure mode was matrix cracking when the maximum strain was less than 0.55 percent. Combining the fatigue life data with the macro-mechanical and microscopic observations, a fatigue life diagram was developed and partitioned into three regions. These regions showed relationships between the maximum applied strain and the dominant damage mechanisms. Also, on a strain range basis, the fatigue lives of the specimens tested under the strain-controlled mode in this study were compared with its counterpart under the load-controlled mode of the previous study. It was found that the fatigue lives for these two conditions were the same within the experimental scatter.

Stiffness Degradation in Metal Matrix Composites Caused by Thermomechanical Fatigue Loading

1993 ◽  
Author(s):  
Sait Aksoy
Keyword(s):  
Metal Matrix Composite ◽  
Elastic Properties ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Transversely Isotropic ◽  
Fatigue Loading ◽  
Thermomechanical Fatigue ◽  
Matrix Composites ◽  
Stiffness Properties ◽  
Cycles To Failure

Damage during thermomechanical fatigue loading of a metal matrix composite is represented by a vector. The undamaged material is characterized by the generalized Hooke’s law for transversely isotropic materials. The residual elastic properties of metal matrix composite are related to the initial elastic properties by the damage vector. The residual stiffness properties are then correlated with the number of fatigue cycles to failure. The ability to use this concept to determine the safe strength requirement for a given cyclic life is discussed.

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