Ballistic impact behaviour of unidirectional fibre reinforced composites

In order to establish the survivability of a composite structure under an impact load, it is important to be able to predict the impact behaviour of composite laminate. In this work, a modified analytical model is proposed to study the impact process of different nose projectiles penetrating into a unidirectional glass fibre reinforced cross ply laminate. This model is based on energy conservation law, where the energy possessed by the projectile is absorbed by the composite laminate by different energy absorbing mechanisms. The energy absorbing mechanisms considered are cone formation of the back face of the composite laminate, deformation of the secondary yarns, tensile failure of the primary yarns, delamination, matrix cracking and friction between the projectile and the laminate during penetration. Analytical formulation is presented for all the energy absorbing mechanism. Using the analytical formulation, ballistic limit, energy absorption and the damage area have been predicted for unidirectional cross ply laminates. The analytical results are compared with the experimental results and found that they are in good agreement.