Paper number 915

MODELLING AND EXPERIMENTAL INVESTIGATION OF THE BALLISTIC BEHAVIOUR OF AN ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE)/THERMOPLASTIC RUBBER MATRIX COMPOSITE

Nikhil Sharma¹,² Debbie Carr¹ Pippa Kelly¹ Christopher Viney²

1Science and Technology Division, Defence Clothing and Textiles Agency, Ministry of Defense, Flagstaff Road, Colchester, CO2 7SS, UK
2Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK

Summary

A finite difference modelling package was employed to determine the ballistic performance and the mechanisms of failure of a 0°/90° ultra high molecular weight polyethylene/thermoplastic rubber matrix composite. NATO standard ballistic testing was completed using fragment simulating projectiles for 4 kg.m-2 to 10 kg.m-2 laminates. The material model, developed at DCTA, when combined with an orthotropic equation of state and a mesh density of 17 mm-2 yielded good correlation with the ballistic data. Post failure analysis, using optical microscopy and ultrasonic c-scan combined with the modelling have shown that the major failure modes for the laminate were: trans-laminar shear, delamination, and tensile failure along the yarn. The delamination size was investigated using an ultrasonic c-scan in the through transmission mode, which compared well with the modelling results. Stress wave investigation, using the model subsequently showed that superposition of elastic waves gives rise to delamination initiation. More than 50% of the energy absorbed by the laminate was due to transfer of momentum by the stress waves.

Keywords

ballistics, body armour, finite difference modelling, ultra high molecular weight polyethylene, post failure analysis, composite failure, delamination, fibre pull-out.