Investigation Of Tensile Strength Of UHMWPE Fibers Extracted From Composite Panels

• Adam Higazi, Computer Engineering, University of Delaware
• Tyler Phommachanh, Mechanical Engineering, University of Delaware

• Ahmad Abu Obaid, Center for Composite Materials, University of Delaware
• Joseph Deitzel, Center for Composite Materials, University of Delaware

Ultra-High Molecular Weight Polyethylene (UHMWPE) panels are the next evolution in protective materials following the success of Kevlar. The processing of the panels can adversely affect the strength of individual fibers. The UHMWPE based composites evaluated in this work were processed at 125℃ under a pressure of 3 ksi (equivalent to an American alligator bite) for 30 minutes. Two strips of fiber are taken from the consolidated panel: one from the edge and another at the center location. These composites strips were fully immersed in Tetrahydrofuran (THF) for 27 days enabling us to extract single fibers without inducing any damage. In terms of micro-damage and strength properties, extracted fibers were compared to virgin fiber.

Using a micro-Instron machine, tension tests were conducted on extracted and virgin fibers, where the fiber is pulled from both fixed fiber ends until breakage occurs. The data from the tension test results for both types were compared. Based on the strength value (4.8 GPa) measured for virgin fibers, the strength reduction for extracted fibers from center and edge locations were estimated. When comparing the bottom layer of each strip, the fibers from the center location exhibit a 14% strength reduction, while the fibers from the edge location showed a 22% strength reduction. From Scanning Electron Microscope (SEM) images, the microdamage modes (such as kinking, cracks and flattening) were captured. Fibers from the bottom-edge location exhibit significantly more damage compared to the bottom-center location, while fibers from the middle-center location exhibit less damage compared to the middle-edge location. Overall, these results reveal that the distribution of processing parameters (temperature and pressure) were not uniform through entire panel during consolidation, compromising the protection performance of the panel. Future research will focus on optimizing the processing parameters of UHMWPE composites to obtain panels with superior performance.