EFFECT OF COMPLIANT PRESSURE PADS ON MICROSTRUCTURE AND PERFORMANCE OF THERMOPLASTIC COMPOSITES

摘要

Ultra-high Molecular Weight Polyethylene (UHMWPE) composite materials are widely used for ballistic protection applications due to their high mass efficiency. The performance of these thermoplastic materials is known to be significantly dependent on processing conditions, including the molding temperature and pressure. It is common in the industry for compliant press pads to be incorporated into the molding process in order to more evenly distribute mold pressure over the surface of the part. This effort examines processing state changes and performance improvements brought about by use of the compliant pads, in the context of previous US Army work to characterize performance gains of select materials with other processing changes, particularly temperature and pressure. The pressure distribution with and without compliant pads is quantified using complementary numerical model and experimental methods. Ballistic results are also presented, and demonstrate a significant performance gain with pressure pad use for a commercial UHMWPE composite material with a polyurethane matrix. Another UHMWPE composite material with rubber-modified matrix is seen to experience more modest performance enhancement. These results are discussed in relation to the measured and modeled local and global applied stress states during processing.