A Modified Iosipescu Method to Study In-Plane Shear Strength of C/SiC Composites at Elevated Temperatures in Air

Background: Accurate evaluation of life-limiting failure behavior is a prerequisite to ensure the successful design and application of ceramic matrix composites (CMCs). Objective: To investigate life-limiting failure behavior of CMCs, it is necessary to evaluate the in-plane shear strength. Methods: In this paper, the in-plane shear strength (IPSS) of two-dimensional carbon fiber reinforced silicon carbide matrix (2D C/SiC) composites at elevated temperatures in air was studied by a modified Iosipescu method. A simplified Iosipescu loading configuration without mechanical connections or a fastening assembly was proposed. Results: According to finite element analysis, an almost pure in-plane shear stress field and an in-plane shear failure mode were obtained. The modified Iosipescu method was adopted to evaluate the IPSS of 2D C/SiC at room temperature (RT), 800 °C, and 1000 °C. The in-plane shear failure mode was observed, and the IPSSs were obtained. Based on the microstructure analysis, the release of the tensile stress at elevated temperatures can account for the increase in the IPSS from RT to 800 °C. The decrease in the IPSS from 800 °C to 1000 °C may have resulted from the oxidation of carbon fibers. Conclusions: The modified Iosipescu method can be used to measure the in-plane properties of CMCs. This study may be beneficial to reveal the failure mechanisms and guide the design of CMCs.