Interfacial Debonding and Slipping of Carbon Fiber-Reinforced Ceramic-Matrix Composites Subjected to Different Fatigue Loading Sequences

摘要

In this paper, the interface debonding and slipping of carbon fiber-reinforced ceramic-matrix composites (CMCs) subjected to different fatigue loading sequences have been investigated using the micromechanics approach. There are two different types of fatigue loading sequences considered: (1) cyclic loading under low peak stress for N1 cycles, and then high peak stress for N2 cycles; and (2) cyclic loading under high peak stress for N1 cycles, and then low peak stress for N2 cycles. Based on the fatigue damage mechanism of fiber slipping relative to matrix upon unloading /reloading, the interface debonded and slip lengths are determined by fracture mechanics approach. The relationships between interface debonding, interface slipping, interface wear, cycle number, fatigue peak stress, and fatigue loading sequence have been determined. The effects of peak stress level, interface wear, cycle number, and loading sequence on the interface debonding and slipping of fiber-reinforced CMCs have been analyzed. With increasing cycle number and the peak stress level, the interface debonding and slipping range increase, leading to the increase of unloading residual strain and hysteresis loops area, and the decrease of hysteresis loops modulus of fiber-reinforced CMCs. The cyclic fatigue hysteresis loops of unidirectional C/SiC composite under multiple fatigue peak stress levels of sigma(max) = 200, 220, and 240 MPa have been predicted. (C) 2016 American Society of Civil Engineers.