Cycle jump technique combined with mean-field micromechanics towards predicting the cyclic response of PA66/GF composites under viscoelastic- viscoplastic regime and damage mechanisms

Abstract

This work proposes a probabilistic micromechanics damage framework to predict the uniaxial and cyclic stress-strain response and progressive damage in random glass-reinforced polyamide composites. Motivated by different microscopic degradation modes observed experimentally, the damage mechanism in the vicinity of the fibers is characterized by the onset and the coalescence of voids, whose evolution can be formulated through a Weibull probabilistic density function. In contrast, the ductile progressive degradation of matrix initial stiffness is analyzed via the continuum damage theory. Towards this end, a 2N+1-phase Mori-Tanaka (MT) method combined with the transformation field analysis approach (TFA) is established within a unified framework. Moreover, the rate-dependent viscoelastic and viscoplastic response of the polymer matrix phase is formulated through a phenomenological model consisting of four Kelvin-Voigt branches and a viscoplastic branch under the thermodynamics framework. Comparison of numerical predictions with experimental data demonstrates the model’s capabilities. In a second step of this work, the micromechanics scheme is combined with the cycle-jump technique in order to simulate moderate and high cycle fatigue tests. This modeling strategy is validated through comparison with experimental results.