A method for identifying the interface shear stress of unidirectional ceramic matrix composites

A method for identifying the interface shear stress of unidirectional ceramic matrix composites (CMCs) under fatigue loading was proposed. A functional relationship between the interface shear stress and the area of the hysteresis loop, the slip strain of the hysteresis loop was established based on the shear lag model by the method of symbolic-graphic combination. A fatigue test of SiC/SiC mini-composites was performed and the hysteresis curves were obtained. Then the interface shear stress under a different number of cycles was identified by inserting the experimental data of the area and slip strain of the hysteresis curves into the functional relation-ship. The identification results using previously introduced methods based on the area or the secant modulus of the hysteresis loop were also examined. To verify these methods, the interface shear stress identified by the three different methods was entered into the shear lag model to simulate the hysteresis curves for the different number of cycles. A comparison between the simulated results and experimental data shows that the proposed method is more appropriate for the composites used in this paper.