LIFE PREDICTION FOR FATIGUE OF T800/5245 CARBON-FIBER COMPOSITES .2. VARIABLE-AMPLITUDE LOADING

This is the second of two papers describing the fatigue response of a [(+/-45,0(2))2]s laminate of the T800/5245 composite system, a modern aerospace material consisting of high-failure-strain, intermediate-modulus carbon fibres in a toughened bismaleimide resin system. In the first paper, the fatigue response in repeated tension, repeated compression, and mixed tension-compression was determined at constant stress levels over a wide range of R values. The results of those constant-amplitude experiments were then used to define a programme of four- and two-block variable-loading experiments in an attempt to derive predictive methods for such loading conditions. Formulae have been developed to predict life under non-linear cumulative damage conditions and empirical data derived to validate the procedures.