Influence of Boundary Conditions on Ceramic/Metal Plates under Ballistic Loads

Nadda Jongpairojcosit

doi:10.4236/msce.2015.37012

Abstract

Ceramic/metal plate is one of the most widely used light weight armors, especially to protect armor piercing (AP) bullet. Experimental investigation of projectile penetration mechanism into the ceramic/metal plate requires costly sensitive equipment to capture impact phenomenon that completes within microseconds. Alternatively, the impact mechanism can be efficiently investigated using numerical simulations. Among recent investigations on the protective capability of this ceramic/metal plates, few only discussed the influence of the boundary effects on the ballistic protection. This study thus aims to examine the effect of boundary conditions by changing shapes of the plate, border constraints and bounded materials in numerical simulation. Material models of the ceramic and the backing metal plate made of aluminium 2017-T6 are selected. The 7.62 AP projectile’s core was modeled by a solid cylinder. The initial projectile velocity was 940 m/s. The plates are represented by either a square or a hexagonal tile. The edges of the plates were fixed or enclosed by a soft epoxy. To investigate the effect of backing plate, a small gap was introduced between some of the ceramic and aluminum interfaces. The results showed that the hexagonal tiles reduce the deformation of the backing plate. The plates bounded by the epoxy exhibit inferior performances compared to the fixed plates. Finally, the small gap between the ceramic and the aluminum interfaces significantly increases the time to stop the projectile.

Highlights

One classical armor material is monolithic steel i.e. Rolled Homogeneous Armor (RHA)
The hexagonal tile can reduce the aluminium deformation compared with the square tile
This can be the result from the shorter distance from the center of the hexagonal tile to its boundary which gives the smaller tile’s deflection

Summary

Introduction

One classical armor material is monolithic steel i.e. Rolled Homogeneous Armor (RHA) This material disperses the impact energy from projectile through its plastic deformation. The limitations of steel armors are their high density, maximum deformation and low protection against Armor-piercing (AP) bullet. At the connecting surface between the ceramic and the backing plate, some of the shock wave will continue moving into the steel and the remaining shock wave will reflect back to the ceramic This wave reflection creates tensile wave in the material. Since brittle materials have low tensile strength, the ceramic starts to crack under the tensile wave The crack from this impact has conical shape which is called conoid. Ceramic fracture under impact has different physical characteristic compare to other armor steel materials because of its brittleness. CL is the longitudinal wave speed in the material and Vrad,crack is the speed of radial crack growth

Numerical Model

Results and Discussion

Conclusion