Foreign Object Damage in an Oxide/Oxide Composite at Ambient Temperature

Foreign object damage behavior of an oxide/oxide (N720/AS) ceramic matrix composite was determined at ambient temperature using impact velocities ranging from 100 m/s to 400 m/s by 1.59 mm diameter steel-ball projectiles. Two different support configurations of target specimens were used: fully supported and partially supported. The degree of post-impact strength degradation increased with increasing impact velocity and was greater in a partially supported configuration than in a fully supported one. For the fully supported configuration, frontal contact stress played a major role in generating composite damage, while for the partially supported case, both frontal contact and backside flexure stresses were the combined sources of damage generation. The oxide/oxide composite was able to survive high energy (similar to 1.3 J) impacts without complete structural failure. The degree of relative post-impact strength degradation of the oxide/oxide composite was similar to that of an advanced SiC/SiC composite observed from a previous study, regardless of the type of specimen support. Like the SiC/SiC composite, impact-damage tolerance was greater in the oxide/oxide than in monolithic silicon nitride ceramics for impact velocities >300 m/s.