Combination of mean-field micromechanics and cycle jump technique for cyclic response of PA66/GF composites with viscoelastic–viscoplastic and damage mechanisms

An accelerated micromechanics framework based on the extended Mori–Tanaka transformation field analysis (TFA) and cycle jump technique is proposed to predict the homogenized response of short glass fiber-reinforced polyamide 66 composites (PA66/GF) under a large number of loading cycles (> 100,000 cycles). The extended theory accounts for microscopic viscoelastic–viscoplastic and damage mechanisms, and realistic microstructures induced by the injection molding process. Toward this end, a number of training cycles are first conducted using the extended Mori–Tanaka TFA to obtain the global evolution functions of material state-dependent variables ( SDVs ) for each phase. These SDVs are extrapolated linearly to a certain jump length with the help of global evolution functions such that direct numerical simulation of the cycles during this interval can be skipped, leading to a large computational cost reduction. After the cycle jump, a set of complete cycles are performed based on the extrapolated SDVs using the Mori–Tanaka TFA simulation to re-establish the global evolution functions. The implementation of the cycle jump procedure is facilitated by introducing an extrapolation control function to allow adaptive jump size control as well as to minimize the extrapolating error. The capabilities of the extended theory with the cycle jump technique have been validated extensively vis-à-vis cycle-by-cycle benchmark calculations under various loading conditions. It has been further verified with the experimental results of actual PA66/GF composites under high-cycle loading beyond which the cycle-by-cycle simulations can achieve.