MULTIAXIAL FATIGUE BEHAVIOR OF UNIDIRECTIONAL PLIES BASED ON EXPERIMENTS UNIAXIAL FATIGUE .1. MODELING

The fatigue behaviour of a unidirectional composite lamina is examined from theoretical and experimental viewpoints. The goal is to establis h a technique to use experimental data from a unidirectional ply under uniaxial fatigue to simulate the behaviour of that ply in multiaxial fatigue loading. Traditional polynomial failure criteria for fatigue a re of limited use because fatigue strength is a function of number of cycles and applied fatigue stress ratio. In practice, a problem such a s a fatigue-loaded complex composite structure containing stress conce ntrations, is subjected to varying stress ratios at different points, especially if material or geometric nonlinearities are involved. Howev er, fatigue testing under a wide range of stress ratios is time consum ing and expensive. Therefore it is important to establish a technique to consider fatigue damage due to arbitrary stress ratio without havin g to perform excessive amounts of testing. Here the theoretical basis of a new model, called the generalized residual material property degr adation model is explained in detail. Copyright (C) 1997 Elsevier Scie nce Limited.