Fatigue life prediction for GRP subjected to variable amplitude loading

A method of predicting lifetime to failure for any glass fibre reinforced composite system subjected to a complex load-time history has been developed. The prediction first requires the generation of a model to characterize the general fatigue response of the particular composite system. Once the models are derived they can be used to predict lifetimes to failure for any load-time history using a modified Miner's damage summation rule and rainflow analysis. Variable amplitude fatigue testing of different GRP materials, using the same load-time history, allowed a comparison to be made between predicted and actual lifetimes to failure and was useful in verifying the accuracy and robustness of the life prediction methodology employed. The results from the life prediction models for three very different GRP systems showed themselves to be accurate predictors of fatigue behaviour for the variable amplitude loading condition investigated.