Quantitative analysis of debris clouds from SiC-fiber-reinforced silicon nitride bumpers

In order to investigate the dynamic response of lightweight ceramic matrix bumpers against hypervelocity projectile impact, silicon carbide continuous-fiber-reinforced silicon nitride matrix composite plates were prepared and subjected to the impact experiments using duralumin projectiles in the velocity range of 2.2 to 3.6 km/s. The debris clouds of the composites were taken by flash, soft X-ray radiography, and the fragmentation of the bumpers and the spatial distribution of the main parts of the debris clouds were quantified in mass, velocity and kinetic energy and compared with those of monolithic duralumin bumpers and monolithic silicon nitride ceramic bumpers. Almost all the average mass and kinetic energy of the in-flight fragments of the composite were smaller than those of the duralumin and monolithic ceramics. The composite provided thinner distributions of the mass and kinetic energy densities of its debris in an area extending farther from the ballistic line for higher impact velocity, while the monolithic ceramics gave massive and energetic debris distributions in a narrow area around the ballistic line. Total mass and kinetic energy of the composite debris were smaller than those of the duralumin, and for impacts over 3 km/s the volumetric energy density of the composite debris was comparable to that of the duralumin. Embedding the fibers to a ceramic matrix was thought to give the composite the heterogeneous microstructure to result in a non-uniform dynamic response of the composite, followed by the bumper fragmentation and the debris dispersion.