Modelling of the energy absorption by polymer composites upon ballistic impact

In this paper we report on the development of a simple model for calculatin g the energy absorption by polymer composites upon ballistic impact. Three major components were identified as contributing to the energy lost by the projectile during ballistic impact, namely the energy absorbed in tensile f ailure of the composite, the energy converted into elastic deformation of t he composite and the energy converted into the kinetic energy of the moving portion of the composite. These three contributions are combined in the mo del to determine a value for the ballistic limit of the composite, V-0. The required input parameters for the model were determined by a combination o f physical characterisation (for the physical and mechanical properties of the composites and the characteristics of the projectile) and from high-spe ed photography (for the size of the deformed region and the cone velocity). As the failure event usually occurred between two of a relatively small nu mber of frames from the high-speed camera, the model predicted a range for V-0. This range of V-0 was compared with experimentally determined values f or three composite systems: woven Nylon-66 fibres in a 50:50 mixture of phe nol formaldehyde resin and polyvinyl butyral resin, woven aramid fibres in a similar matrix and Dyneema UD66 (straight gel-spun polyethylene fibres la id in a 0/90 fibre arrangement in a thermoplastic matrix). In all cases, th e experimentally measured values of V-0 were found to lie within the range predicted by the model. The size of the deformed region, formed through she ar deformation, on the back face of the composite was found to relate direc tly to the in-plane shear modulus of the material. Perhaps the most surpris ing result was that the dominant energy absorbing mechanism was found to be the kinetic energy of the moving portion of the composites. Crown Copyrigh t (C) 2000 Published by Elsevier Science Ltd. All rights reserved.