Foreign Object Damage in an Oxide/Oxide CMC Subjected to Tensile Preloading

Abstract

Foreign object damage (FOD) phenomenon of an N720/alumina oxide/oxide ceramic matrix composite (CMC) was determined previously using 1.59 mm-diameter hardened steel ball projectiles using impact velocities ranging from 150 to 350 m/s at a normal incidence angle. Target specimens were impacted under tensile preloading with three different levels of load factors of 0, 30, and 50%. Difference in impact damage between no-preload and pre-load was significant particularly at 350 m/s with the highest load factor of 50%. A fracture mechanics approach was used to predict post-impact strength as a function of load factor and was assessed its applicability using the experimental data.