Edge effects may cause reduced ballistic performance close to the edge of armoring parts. When a ballistic test of an armor sample is performed, it is important to define whether this test is aimed to the main area (MA) of the sample or to the structurally weak areas (SWA) near its edges. Some standards define excluded zone (EZ) to avoid test within SWA, but for transparent armor (TA) the available data regarding the extent of the SWA is rather limited, resulting in possibly insufficient EZ. In this work, typical TA samples were tested against Kinetic Energy (KE) and Fragment Simulating Projectile (FSP) threats, at both MA and edge related SWA, and the differences in the ballistic performance were examined. The obtained results suggest that the edge effect extends to at least 100-150 mm from the edges. Finally, we recommend that for ballistic performance purposes, explicit definitions of sample size, impact location and shooting sequence, should be considered to be incorporated into ballistic standards to ensure repeatability of the tests.
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