Ballistic Resistance of Multi-Layered Sandwich Composites

Abstract

In this paper, an armor structure consisting of hybrid sandwich composites is studied. The ballistic resistance of hybrid sandwich composites is investigated by ballistic events with high velocities of armor piercing projectiles. For analyzing the ballistic phenomena, the multi-layered structure composed of aluminum alloy layer, ceramic seam, 2-D plain woven textile composite skins is considered. To get the high-speed photographs of ballistic penetration and developing, a high-speed camera is used. And also to get a better understanding of the dynamic behavior of multi-layered targets, the three-parameters; velocity, displacement and acceleration are considered. The dynamic response of hybrid sandwich targets is calculated by a simple empirical modeling and experimental data of target and bullet in the impacted bodies. As widely used in armor structures, silica (SiO2) and alumina (Al2O3) ceramics are often used as a backing material of hybrid composition to improve the ballistic resistance of the structure. We used silica ceramics as backing materials in this study. To absorb the shock of the hybrid structure, Kevlar, ceramics and high density materials with reduced weight have been used as backing materials. Heavy materials with high strength such as Berlium can't be used because of its high cost and rareness. The importance of the core materials in the hybrid composites shows higher by its essential role of armored structure. A various materials have been used as core materials because of its high strengths, but the susceptibility to impact damage limited its application. Woven fiber composites are one of best candidates to armor materials because of its low weight and high strengths. Hybrid composites enables the composite structure to armor the ballistic impact and reduces more real weight than using single composite material. To reduce the number of tests and effectiveness of protecting from impact damage is better than using single woven planar composites. From aforementioned multi-layered composites, we can see that the hybrid sandwich composite has been continuously interested as armor structures due to their high impact resistance. So, there is needed a better understanding of impact behavior and a numerical modeling on this multi-phase structure. With this structural good point, the main objective of this paper is to develop a more effective impact modeling with the use of the empirical and numerical methods considered together. Another objective of this paper focuses on the ballistic resistance of hybrid sandwich composite materials comparing the single use of planar woven textile for ballistic survivability. In addition the present study has tried to solve the impact problems by using the empirical equations and the experimental data together. All these problems are assessed by comparing our predictions with those are table in the literature. 2. Computational Methodology To solve the impact and penetration problems 1-3 , this study uses the cohesive element modeling and two simple contact separation algorithms for un-cracked or cracked elements that are formed between the target and the projectile during the high speed impact. For an appropriate time step for calculations, this study introduces an explicit integration method, i.e. the central difference method, that is very useful for studied in which loading at high rates are expected, such cohesive elements. The present research uses an analytical impact modeling presented in Ref. (4) and the cohesive element method to find the dynamic response of thin plates subjected to various values of impact velocity. This study shows that one simple analytical impact modeling based on empirical equations, a numerical scheme and the cohesive element modeling can predict the projectile position, velocity and forces. To understand the dynamic response of thin plates, this study uses a simple empirical approach suggested by Ref.