Thermal-mechanical behavior of a SiC/SiC CMC subjected to laser heating

With ceramic matrix composites (CMCs) being targeted for use as hot section components in gas turbine engines, it is important to understand the thermal-mechanical behavior of these materials within extreme application environments. This work focused on characterization of the in-situ response of a melt-infiltrated (MI) composite (i.e., a laminated Hi-Nicalon™, BN-interphase, melt-infiltrated (MI) SiC matrix composite) subjected to combined thermal-mechanical loads representative of intended operational environments. Laboratory scale test specimens were loaded in uniaxial tension at room temperature and at elevated temperature under both isothermal and non-isothermal conditions. During laser heating experiments, a number of in-situ techniques enabled monitoring of damage formation, strain evolution, and temperature up to failure at 1150 °C. Results indicate that applying mechanical loads axially in the presence of thermal gradients may induce interply delamination cracks not observed after CMC test specimens are loaded axially under isothermal conditions.