Life prediction of composite materials subjected to long term mechanical/environmental loading condition

A multi-scale mechanism-based life prediction model is developed for high-temperature polymer matrix composites (HTPMC) under thermo-oxidative aging conditions. Life prediction model is based on stiffness and strength degradation in unidirectional HTPMC under accelerated thermo-oxidative aging condition. A multi-scale model based on continuum damage mechanics to predict stiffness degradation and progressive failure due to degradation of inter-laminar shear strength is developed for unidirectional composite. Using continuum damage mechanics one can relate the behavior of composites at micro-level (representative volume element) to the macrolevel (structural element). Thermo-oxidative aging is simulated with diffusion-reaction model in which temperature, oxygen concentration and weight loss effects are considered. For fiber/matrix debond growth simulation, a model based on Darcy's laws for oxygen permeation in the fibermatrix interface is employed, that, when coupled with polymer shrinkage, provides a mechanism for permeation-controlled debond growth in HTPMC. Viscoelastic regularization in the constitutive equations of the cohesive layer used in this model not only mitigates numerical instability, but also enables the analysis to follow load-deflection behavior beyond the point of peak failure load. Benchmark of model prediction with experiment was carried out to establish proof-of-concept.