Life prediction in continuous fiber metal matrix composites subjected to environmental degradation

A model is discussed herein for predicting damage evolution in continuous fiber metal matrix composites subjected to environmental degradation. Due to multiple nonlinearities, the model utilizes a finite element framework derived from thermodynamics and continuum mechanics. Matrix inelasticity, damage evolution, and degradation of mechanical properties due to oxidation-related effects are also included within the model. Matrix inelasticity is modelled with the Bodner anisotropic hardening viscoplastic model. Damage growth such as surface cracking, matrix cracking, fiber-matrix debonding, and fiber cracking is modelled via the inclusion of cohesive zone elements in the unit cell. The locations of these elements are chosen to correspond with experimentally observed damage. Environmental degradation is accounted for by including degraded material properties which result from oxygen-induced changes in microstructure. The current paper briefly summarizes the formulation utilized by the authors to solve this problem, and recent results are discussed. Specifically, results are given for a four-ply unidirectional SCS-6/Ti-21S composite subjected to elevated temperature isothermal monotonic and fatigue loading cases.

Life prediction in continuous fiber metal matrix composites subjected to environmental degradation Conference Paper