New Approaches to Modeling and Simulation of Ultra High Molecular Weight Polyethylene

Abstract

This work deals with numerical simulations of impact problems on fiber-based composite armor using the commercial finite-element-code ANSYS AUTODYN. Having presented some basic knowledge on the theory of numerical simulation in AUTODYN, two recently published approaches for modeling impact on the selected composite (Dyneema® HB26) are explained. While both of them make use of a nonlinear-orthotropic material model implemented in the AUTODYN-code, they differ in the way how the highly inhomogeneous microstructure of HB26 is represented geometrically. Lässig chooses a fully homogeneous description, whereas Nguyen discretizes the composite into sublaminates, which are kinematically joined at the surfaces and breakable when a certain contact-stress is reached. In order to validate the two approaches, the response of HB26- samples impacted by handgun-projectiles was determined experimentally and compared to the corresponding numerical results. Unfortunately, a poor agreement between experimental and numerical results was found, which gave rise to the development of an alternative modeling approach. In doing so, the composite was subdivided into alternating layers of two different types. While the first type of layers was modeled with open-literature properties of UHMWPEfibers, polymer-matrix-behavior was assigned to the second type. Having adjusted some of the parameters, good agreement between experiment and simulation was found with respect to residual velocity and depth of penetration for the considered impact situations.