Role of pre-stressing on anti-penetration properties for Kevlar/Epoxy composite plates

Abstract

Bulletproof vest capability improvement is considered an important issue, especially for vests made from composite materials. Composite materials consisting of Kevlar 29/Epoxy at different volume fractions of 30, 40, and 60% were made to produce the test samples used in this work. These samples consisted of two plates; the plates were gathered within a frame, making a gap of 10 mm between them. Two sets of test samples were used. The first set consisted of two plates in their normal state (set A). In contrast, the second set (set B) was exposed to bending load generating pre-bending stress in the plates before the ballistic test. A 9 mm handgun was used to shoot the bullets. Chronographs were used to detect the projectiles' speed before and after hitting the samples. The samples were labeled according to the fiber volume fraction (A30 , A40 , A60 , B30 , B40 , and B60). Each sample was exposed to three successive shots. The results showed that B30 decreases the final velocity of the projectile by 45% compared to set A30 when the plates were loaded with 120 MPa stress. Increasing the stress value in sample B30 from 50 MPa to 120 MPa causes an increase in the sample's absorbed energy value of about 47%, 22%, and 1% for first, second, and third shots, respectively. A similar pattern of results has been obtained for other volume fractions.