Rw. Neu, A MECHANISTIC-BASED THERMOMECHANICAL FATIGUE LIFE PREDICTION MODEL FOR METAL-MATRIX COMPOSITES, Fatigue & fracture of engineering materials & structures, 16(8), 1993, pp. 811-828
The framework for developing a mechanistic-based life prediction model
for metal matrix composites is described. For a composite consisting
of unidirectional silicon carbide fibers in a titanium aluminide matri
x, SCS-6/Ti-24Al-11Nb (at%) [0]8, three dominant damage mechanisms wer
e identified: (1) matrix fatigue damage, (2) surface-initiated environ
mental damage, and (3) fiber-dominated damage. Damage expressions were
developed for each mechanism along with a method for determining the
constants. The damage is summed to obtain the total life. The model is
capable of making predictions for a wide range of histories, includin
g isothermal fatigue at different frequencies and stress-ratios, therm
omechanical fatigue (TMF) under in-phase and out-of-phase cycling cond
itions, thermal cycling at constant stress, and stress holds at either
maximum or minimum stress. Considering the wide range of cyclic condi
tions, the predictions compare favorably with experiments. In addition
, the controlling damage mechanism for each history is predicted.