Foreign Object Damage in an Oxide/Oxide Ceramic Matrix Composite Under Prescribed Tensile Loading

Abstract

Foreign object damage (FOD) behavior of an N720/alumina oxide/oxide ceramic matrix composite (CMC) was characterized at ambient temperature by using spherical projectiles impacted at velocities ranging from 100 to 350 m/s. The CMC targets were subject to ballistic impact at a normal incidence angle while being loaded under different levels of tensile loading in order to simulate conditions of rotating aeroengine airfoils. The impact damage of frontal and back surfaces was assessed with respect to impact velocity and load factor. Subsequent postimpact residual strength was also estimated to determine quantitatively the severity of impact damage. Impact force was predicted based on the principles of energy conservation.

Tensile and fatigue behavior of oxide/oxide ceramic matrix composite with simulated foreign object damage in combustion environment

“…Although surviving catastrophic failure, most CMCs on the verge of full penetration by impact show about 40%-60% reduction in their tensile strength. [8][9][10]15 In this regard, a 66% reduction in strength for the CMC with the deeper dent is not surprising. The stress-strain plots in Figure 8 also show that the dented test coupons, i.e., test coupons with pre-existing damage, behave slightly less stiffly upon loading than the undamaged test coupon.…”

“…A number of studies have been previously performed on FOD evaluation of CMCs. [8][9][10][11][12][13][14][15] Overall, CMCs exhibit slightly greater resilience to FOD in comparison to monolithic ceramics. Although not failing catastrophically, most CMCs on the verge of full penetration by impact show about 40%-60% strength degradation.…”

“…The extent of FOD in a CMC depends on several variables including impact velocity, impact angle, impactor shape, material type, and environmental conditions. A recent study by Kedir et al investigated damage both as a function of impact velocity and preload in tension, the latter expected in actual rotating aeroengine foils. It was observed that the extent of damage and overall strength reduction depended both on the amount of preload as well as the impact velocity.…”

“…Although not failing catastrophically, most CMCs on the verge of full penetration by impact show about 40%-60% strength degradation. [8][9][10]15 The extent of FOD in a CMC depends on several variables including impact velocity, impact angle, impactor shape, material type, and environmental conditions. A recent study by Kedir et al 8 investigated damage both as a function of impact velocity and preload in tension, the latter expected in actual rotating aeroengine foils.…”

“…Impact by foreign particles like flying debris can damage the CMCs and result in a significant loss in their load carrying capacity. A number of studies have been previously performed on FOD evaluation of CMCs . Overall, CMCs exhibit slightly greater resilience to FOD in comparison to monolithic ceramics.…”