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The ballistic performance of state-of-the-art silicon carbide armor material can exhibit a fairly wide variability in certain test configurations, which, it is proposed, may be due to the presence of large (>0.1 mm), rare defects, termed, herein, "anomalous" defects. SiC rubble resulting from ballistic tests was examined, as were quasi-static test samples. Ballistic fragment fracture surfaces revealed large carbonaceous defects that seemed to affect fracture path and mode. Low-strength biaxial flexure samples demonstrated similar defects (>0.1 mm) as failure origins. Carbonaceous defects similar in appearance but smaller in size were also found at the fracture origins of SiC bend bars. Frequently, alumina inclusions were found within the carbonaceous discontinuities. These alumina inclusions may cause the graphitic regions to form during sintering. The random distribution of such large, rare carbonaceous discontinuities from sample-to-sample, as well as batch-to-batch variability, may explain high ballistic variability for SiC armor ceramics. [ABSTRACT FROM AUTHOR]

Several hot-pressed and sintered SiC variants were impacted with tungsten-carbide (WC) spheres at velocities up to 1700 m/s. Ballistic response curves of areal density penetrated as a function of impact velocity were generated to compare ceramics for ballistic applications. Observed response curve features are shown to be similar to those observed for metal impacts. Ballistics penetration models that captured these features for metal targets were utilized to analyze the ceramic data. Visual examination of damage type and extent suggested that cavity expansion expressions for target resistance might help to quantify the strength of fully confined, damaged, comminuted ceramics. The experimental results, visual observations, and preliminary analysis using a ballistics penetration model are presented. [ABSTRACT FROM AUTHOR]