Nanoindentation on peeled high-performance polymeric fibers reveals failure mechanisms

High-performance fibers are key to many structural and lightweight applications as they are the main reinforcing components of continuous fiber-reinforced composites and fabrics. These fibers are drawn from synthetic polymers such as poly(p-phenylene terephthalamide) (PpPTA) or ultrahigh-molecular-weight polyethylene (UHMWPE). During the drawing process, highly oriented and crystalline nanofibrils of 10–50 nm width form and assemble into larger bundles of 100–500 nm width, thereby creating a hierarchical microstructure. Although it is known that hierarchy generally improves the properties of materials, its role in the failure of synthetic fibers has not been studied. In particular, measuring properties at the intermediate submicrometric scale is challenging. To better understand the role of this organization in the mechanical performance of fibers, the research groups of Yuris Dzenis at the University of Nebraska–Lincoln and Kenneth Strawhecker at the US Army Research Laboratory have taken up the challenge and studied the mechanical interactions between the bundles. Their results were published in ACS Applied Materials and Interfaces (doi:10.1021/acsami.9b23459).