Effect of Gap Condition Between Two Composite Plates in Ballistic Resistance Tests

There is a great need to improve the efficiency of bulletproof vests, especially those, which made from composite materials for many reasons including protecting lives of individuals and finding the best materials and arrangements that keeps the environment clean and other technical and economic reasons. Researches that included the above needs are divided into several topics including development of crystalline structure of the composite materials, studying the use of additives to composite materials or hybrid composite materials, and there are researches on the type of materials used and the number of layers and geometry. In this work, plates of Kevlar 29/Epoxy with 30, 40 and 60% fiber volume fractionsare manufactured using 4 layers of Kevlar. Samples are assembled from two plates gathered within a frame leaving a gap between them. Three types of samples are used depending on gap condition, the first with free gap, the second kept with pressurized gap, and the third was vacuumed. The pressure level reached ±35 kPa. The samples are exposed to ballistic test with 9mm bullets. The bullet speeds before and after impacts are recorded. It is noticed that 39% speed reduction is gained from the 30% Vf when the sample is pressurized by 35 KPa. This value increased to 42% for Vf 40% about 46% for Vf 60%.