Numerical Modelling of Ultra-High Molecular Weight Polyethylene Composite under Impact Loading

Numerical models are investigated and refined for analysis of ultra-high molecular weight polyethylene (UHMW-PE) composite under ballistic and hypervelocity impact. An existing non-linear orthotropic continuum model implemented in a commercial hydrocode (ANSYS® AUTODYN®) was evaluated using a previously published material data set. It was found that the material through-thickness shear performance was artificially degraded as a result of coupling to the through-thickness tensile properties, significantly affecting the model accuracy for impact velocities in the ballistic regime. In order to correct for this, the composite laminate was discretized into sub-laminates joined by bonded contacts breakable through a combined tensile and shear stress failure criterion. The sub-laminate method allows the through-thickness tension and shear failure to be decoupled in the bulk material. This method was investigated and validated against experimental ballistic and hypervelocity impact tests. Simulations showed improvement in ballistic limit predications for thin targets under low velocity impact. Prediction of target deflection is also significantly improved compared to the baseline model in terms back face deformation. Under hypervelocity impact, good agreement with the experimental ballistic limit and residual velocities is still maintained, with a small variation between the new and baseline models. A third validation case was performed to investigate the model performance with thicker targets (50 mm) for impact velocities between the two baseline studies. Accuracy for this condition is poor and remains a challenge for the numerical model.