Effect of BoundaryConditions on the Back Face Deformations of Flat UHMWPE Panels

Report No. ARL-RP-0514
Authors: Timothy G Zhang; Sikhanda S Satapath y; Lionel R Vargas-Gonzalez; Shawn M Walsh
Date/Pages: December 2014; 18 pages
Abstract: The back face deformation (BFD) characteristics are important in assessing the load transfer from the helmet to the head due to blunt impact. We carried out a series of ballistic experiments to investigate the BFD in flat panels made of Ultra-High-Molecular-Weight-Polyethylene (UHMWPE). Spherical projectiles were used at velocities in which the panels were not perforated. In our study, we used three different boundary conditions, namely, clamped-corners, clamped-edges and free boundary condition (the panels are suspended by two strings). The experiments were modeled in LS-DYNA. Existing composite material models were found not to be adequate in capturing the observations. Therefore, we calibrated the constitutive parameters of a composite material model to the experimental conditions. Tiebreak contacts were used to model the delaminations in the composites. The calculation showed reasonable agreement with the experimental data for the clamped-corners and free boundary condition cases for the peak BFD, remaining thickness of the composite and the delamination behavior. The model is useful to assess the size-effects and boundary proximity effects under blunt impact scenarios.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2014