Predicting Fatigue Life of Composite Laminates Subjected to Tension-Tension Fatigue

Abstract

A recent two-parameter model, successfully employed to predict the flexural fatigue lifetime of randomly oriented glass fibre reinforced plastics, is applied to experimental data available in the literature, concerning carbon fibre reinforced plastic-laminates subjected to tension-tension fatigue. It is shown that the model accurately reproduces not only the classical S-N curve, but also the probability of failure under assigned loading conditions, if its constants are calculated by a minimum number of experimental tests. However, the results also demonstrated that the proposed method fails in describing the residual strength decay with cycle evolution, resulting in very conservative estimates. This was unexpected, because the formula for fatigue life directly derives from a precise assumption on the law governing the strength degradation. From the results presented, it is concluded that the model must be considered as an empirical formula, yet efficient in predicting fatigue life.