Damage and fracture of fiber-reinforced ceramic-matrix composites under thermal fatigue loading in oxidizing atmosphere

Abstract

In this paper, the damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) subjected to thermal cyclic fatigue loading at elevated temperatures in oxidizing atmosphere are investigated. The temperature/cyclic dependent fiber/matrix interface shear stress is determined as a function of testing temperature, applied cycle number and material properties, which affects multiple thermal fatigue damage mechanisms. The microstress field of the thermal fatigue damaged composite is analyzed using the Budiansky-Hutchinson-Evans shear-lag model, considering matrix stochastic cracking, fiber/matrix interface debonding/sliding and fibers fracture. The matrix stochastic cracking, fiber/matrix interface debonding and sliding, fibers fracture in the interface damage zones are determined using the micromechanical approach. The relationships between the thermal fatigue cycling, multiple thermal fatigue damage mechanisms, fatigue hysteresis-based damage parameters and thermal fatigue lifetime are established. The effects of fiber/matrix interface properties, fiber radius, fiber volume fraction, matrix crack spacing and fatigue peak stress on thermal fatigue damage evolution in fiber-reinforced CMCs are analyzed. The thermal fatigue damage evolution and lifetime prediction of two different fiber-reinforced CMCs, i.e., cross-ply SiC/MAS and 2D SiC/SiC composites, subjected to thermal cycling fatigue in oxidizing atmosphere are predicted.