Long-term life prediction of woven CFRP laminates under three point flexural fatigue

This technical contribution reports details of an investigation of the long-term flexural fatigue life behavior of plain weave carbon 3K-70P/epoxy (CFRP) laminates using accelerated testing methodology (ATM) coupled with time temperature superposition principle (TTSP). Initially, dynamic mechanical analysis (DMA) tests were performed on the CFRP laminates to determine the time-temperature shift factors followed by constant strain rate (CSR) tests at different temperatures to construct the creep strength master curve. The time-temperature shift factors were computed using an automated curve shifting programme. Horizontal shift factors were found to follow Arrhenius linear relationship for both above and below glass transition temperatures with different gradients. The scatter in the strength data was considered using Weibull analysis. Flexural fatigue tests were then conducted at different temperatures and loads. Finally, the master curves of flexural fatigue strength were constructed to predict the life of the CFRP laminates at arbitrary frequencies and load cycle ratios. Predicted fatigue behavior at non-default test parameters was found to be in good agreement with experimental data.