## 3 Results and Discussion
A typical front and side view of the sample after ballistic impact was taken for the pure-matrix sample after the SA test and is shown in Figure 8.  
Generally, three stages occur during the projectile impact [21]: shattering, erosion, and catching. Shattering is the primary stage in defending the hard-core projectile. During the shattering stage, the projectile impacts the ceramic surface. A shock wave is generated and reflected from the back of the ceramic/backing interface. The reflected tensile wave initiates the damage accumulation and cracking in the ceramic. The interaction between projectile and ceramic also results in deforming, shattering, or eroding of the projectile. During the erosion stage, the ceramic is already cracked but still prevents the projectile or fragments from penetration by the erosion mechanism. In the last catching stage, the ceramic and its back-plate stops the projectile and fragments by momentum transfer. The interaction between projectile and ceramic that results in the deforming or shattering of the projectile is a key process in defeating the projectile because the deformed, or even shattered, projectile dissipates its kinetic energy to a larger area and reduces the stress generated. To effectively deform or shatter the projectile, the ceramic needs to have sufficient hardness. [PERSON] et al. [22] reported that the hardness was negatively related  
Figure 8: The images for the pure-matrix sample after the SA test; (**a**) front view (the ballistic hitting sequence was labeled); (**b**) side view. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample Type**} & \multicolumn{3}{c}{**CA Test Results**} & \multicolumn{3}{c}{**SA Test Results**} \\ \cline{2-6}  & \multirow{2}{*}{**Hit Result**} & \multirow{2}{*}{**BFS Depth of Hits (mm)**} & \multicolumn{3}{c}{**Hit Result(s)**} & \multirow{2}{*}{**The Maximum BFS Depth (mm)**} \\ \cline{3-3} \cline{5-6}  & & & **1 st** & **2 nd** & **3 rd** \\ \hline Uniform-layered & **PP a** & **7.2** & PP & PP & PP & 16.4 \\ Gradual-layered & **PP** & **5.6** & PP & PP & PP & 15.7 \\ Pure-matrix & **PP** & **9.1** & PP & PP & PP & 15.7 \\ SSIC & **PP** & **11.2** & - & - & - & - \\ \hline \hline \end{tabular}  
a: The bullet was partially penetrated. - Not measured  
\end{table} 
Table 3: Ballistic test results of the laminated SiC ceramics tested in conjunction with a flexible armor jacket (the CA test) and stand-alone (the SA test). to the depth of penetration (DOP) for several SiC ceramics, including solid-state sintered SiC and liquid-phase sintered SiC. [PERSON] et al. [12] reported a decrease in the penetration resistance of the laminated ceramics with low-hardness interface layers and found that introducing the interface layer at the backside affected penetration resistance less. The interface layer in this study had very low Vickers hardness due to the 50 wt.% of BN, thus the interface layer may not provide an effective projectile-fracturing effect. To guarantee the projectile-fracturing effect of the laminated ceramics, no interface layer was introduced to the first 0.8 mm in the strike face side. As a result, the uniform-layered and gradual-layered samples both successfully defeated the 5.8 mm bullet, indicating a sufficient hardness of the sample to deform or shatter the bullet. In this study, the laminated SiC was found to provide better energy absorption ability under the ballistic impact compared to the solid-state sintered SiC when used in conjunction with a flexible armor jacket. The BFS depths of the four types of the samples in the CA test were in the following sequences: gradual-layered \(<\) uniform-layered \(<\) pure-matrix \(<\) SSIC. The laminated SiC, even with no interface layer, had a BFS depth of 20% less than that of the SSIC. As can be seen in Table 2, the pure-matrix sample had a higher strength and a higher toughness but a slightly lower hardness than that of SSIC. [PERSON] et al.