Prediction of Fatigue Life of Composite Laminates using Micromechanics of Failure

TL;DR: In this paper, a methodology was presented to predict fatigue life of composite laminates based on fatigue life prediction of constituents, i.e., the fiber, matrix and interface, using micromechanics of failure.

Abstract: Many tests are required to predict the fatigue life of composite laminates made of various materials and having different layup sequences. Aiming at reducing the number of tests, a methodology was presented in this paper to predict fatigue life of composite laminates based on fatigue life prediction of constituents, i.e. the fiber, matrix and interface, using micromechanics of failure. For matrix, the equivalent stress model which is generally used for isotropic materials was employed to take care of multi-axial fatigue loading. For fiber, a maximum stress model considering only stress along fiber direction was used. The critical plane model was introduced for the interface of the fiber and matrix, but fatigue life prediction was ignored for the interface since the interface fatigue strength was presumed high enough. The modified Goodman equation was utilized to take into account the mean stress effect. To check the validity of the theory, the fatigue life of three different GFRP laminates, UDT[], BX[]S and TX[]S was examined experimentally. The comparison between predictions and test measurements showed good agreement.