Long-term fatigue strength prediction of CFRP structure based on micromechanics of failure

Abstract

A prediction method for the fatigue strength of polymer composites under arbitrary frequency, load ratio and temperature was developed with the combined method of the micromechanics of failure (MMF) developed by Ha and the accelerated testing methodology (ATM) developed by Miyano and Nakada. The time- temperature dependent master curves of MMF/ATM critical parameters were constructed by tensile and compressive static and fatigue tests for the longitudinal and transverse directions of unidirectional CFRP under various temperatures based on the three-dimensional micromechanics of fibers and matrix resin and the time- temperature superposition principle which holds for the viscoelastic behavior of matrix resin. These master curves can be used to predict the fatigue strength of composite structures with multi-directional laminations at any time, temperature, and number of cycles to failure. The applicability of MMF/ATM combined method to predict the long term strength of CFRP structures was experimentally confirmed by prediction of the open hole compression fatigue strength of the quasi-isotropic CFRP laminates.