Effect of coupon geometry and preload on flexural properties of oxide ceramic matrix composites

Oxide ceramic matrix composites (O-CMCs) have a high potential for usage in thermal protection systems or combustion chambers because of their low weight, temperature- and corrosion stability as well as non-brittle failure behavior. Mechanical property changes over their lifetime due to operational loads are not well understood. Moreover, mechanical properties from planar samples under laboratory conditions often differ substantially from upscaled components with complex geometries. In this work, the influences of curvature and preloading conditions were investigated experimentally using modeling to determine boundary conditions. Effects of curvature and trends among preload conditions were determined, with high-cycle-fatigue-preload (HCF) reducing strength and Young’s Modulus by 15% compared to their original values where low-cycle-fatigue-preload (LCF) had smaller effect. The low impacts of high temperatures and small-to-medium loads on the properties of O-CMCs makes them an interesting choice for high-temperature combustive environments.