Enabling multi-stage high-temperature strength evolution prediction of ceramizable composites using a novel multi-field coupled model

Strength varies significantly under high-temperature environment, due to the inherent thermomechanical behavior of the ceramizable material and its coupling with possible chemical reactions. The complexity amplifies for composite materials, considering their multi-phase and multi-scale features, and more importantly, their complicated chemical reactions under high-temperature service conditions. This study proposes an innovative multi-field coupling theory framework for predicting the multi-stage evolution behavior of high-temperature mechanical properties of a ceramizable composite, through incorporating an extended chemical kinetics method, coupled deformation, mass diffusion and heat conduction. The developed model enables direct coupling and simultaneous solving of physical, chemical and thermal variables. It captures well the degradation of mechanical properties for the initial stage and the increase of strength for the later stage, along with the increasing of temperature. The validated model also enables well prediction of time-dependent mechanical properties at high service temperature, with an average error of 8.67% against experimental measured results. The developed method can serve as a general method for the prediction of high-temperature mechanical property of thermal protection composites and structures.