Effects of Target Size on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Steel Ball Projectiles

Foreign object-damage (FOD) phenomena of an N720/alumina oxide/oxide ceramic matrix composite (CMC), impacted by 1.59-mm spherical chrome steel projectiles up to Mach 1, were assessed at ambient temperature at a normal incidence angle in both partial and full supports. The impact damage was in the form of craters, matrix/fiber tow breakage, compaction of the material, delamination and cone cracks, and their occurrence and degree depended on both impact velocity and type of target supports. The partial support resulted in significant damage with increasing impact velocity, accompanying substantial strength degradation. The presence of tensile stress and presumably stress wave interaction at the backside of a target could have been responsible for greater impact damage in partial support. Although the CMC targets impacted at 340 m/s were on the verge of being penetrated, the targets still survived catastrophic failure retaining about 68% of the as-received strength, indicative of relatively superior FOD resistance as compared to monolithic ceramic counterparts. A quasi-static analysis of impact force prediction was made based on the energy balance principle and was validated indirectly using the experimental data on frontal impact damage size. F. Zok-contributing editor Manuscript No. 34997.

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Restitution of Impacting Projectiles in Ceramic Matrix Composites Subject to Foreign Object Damage

Faucett

Mattison

Choi

2022

Journal of Engineering for Gas Turbines and Power

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Accurate assessments of rebound velocity of a projectile in impact events for ceramic matrix composites (CMCs) are important since the rebound velocity affects the degree of resultant impact damage in both CMC targets and projectiles. A series of in-depth characterizations of coefficients of restitution (COR), which is defined as rebound velocity divided by impact velocity of a projectile, was made using various types of gas-turbine grade ceramic matrix composites (CMCs) in conjunction with dynamic imaging and data-acquisition systems. Both the impact aspects and the coefficients of restitution were characterized as a function of impact velocities ranging from 150 m/s to Mach 1 and were analyzed with respect to materials' key properties. An important experimental observation was that regardless of types of CMCs employed, the corresponding CORs at an impact velocity of 350 m/s (i.e., Mach 1) yielded consistently the same value close to 0.1-0.2. The temperature effect in COR was found to be minor to 1100oC as assessed with the specialty SiC/SiCs, also independent of environmental barrier coatings. The coefficients of restitution were also determined in other materials systems such as advanced monolithic ceramics and some metallic materials in an attempt to construct an overall COR map in response to related foreign object damage (FOD) events.

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Effects of Target Size on Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Steel Ball Projectiles

Cited by 3 publications

References 26 publications

Foreign Object Damage in Ceramic Matrix Composites

Foreign Object Damage in Ceramic Matrix Composites

Foreign Object Damage by Spherical Steel Projectiles in an N720/Alumina Oxide/Oxide Ceramic Matrix Composite

Restitution of Impacting Projectiles in Ceramic Matrix Composites Subject to Foreign Object Damage

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