Single Curvature Preforming of Ultra-high Molecular Weight Polyethylene (UHMWPE) Composites

Report No. ARL-TR-8778
Authors: Michael Yeager and Travis Bogetti
Date/Pages: September 2019; 33 pages
Abstract: Ultra-high molecular weight polyethylene (UHMWPE) composites are highly oriented fiber-reinforced materials commonly used in ballistic protective applications, where the as-manufactured quality and performance of the finished part are closely related. UHMWPE composites, commercially available as flat sheets, require a multistep process to be transformed into compound curvature parts. A commonly used process involves preforming a UHMWPE stack at elevated temperature (i.e., thermoforming) followed by high-pressure consolidation between matched metal tooling. In this process, the individual sheets often wrinkle due to the large in-plane shear deformation necessary to conform them into complex shapes. Wrinkling obscures the relationship between the process parameters and individual deformation mechanisms of the preforming because wrinkling and shear are coupled with compound curvature geometries. A single curvature preforming apparatus (i.e., preformer) is developed here to isolate wrinkling from the material response and study the complex deformation mechanics during processing. A finite-element model of the preformer is also developed and used to gain further insight into how various processing parameters influence material response during preforming. Understanding the influence of processing parameters on material deformation will facilitate processing and design strategies to manufacture complex shape UHMWPE parts with improved performance.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2019