PNNL

Abstract

High recyclability is one of the important features in sustainable composites. Thus, this work explores a type of composite — thermoplastic matrix reinforced by thermoplastic fibers — that can be fully recycled through melting both fibers and matrix, and then reshaped into fibers and matrix again to maximize the efficiency in material re-use. Such composites are often called self-reinforced composites (SRCs) or polymer-fiber-reinforced polymers (PFRPs), simplifying the implementation of closed-loop recycling, re-manufacturing, and re-use to support sustainability in composites. In this work, a representative PFRP was exemplified using unidirectional (UD) ultra-high-molecular-weight polyethylene (UHMWPE) fibers embedded in a high-density polyethylene (HDPE) matrix. The effects of compression modeling temperature and pressure on the mechanical and morphological behaviors of the filament-wound PFRPs with various fiber volume fractions (Vf) were experimentally investigated, and this data was never comprehensively provided in the literature. The results elucidate the evolution of cross-sectional morphologies, axial tensile properties, and failure progression of the PFRPs due to temperature-induced thermal melting, pressure-induced misalignment of polymer fibers, as well as Vf-induced structural variance. Moreover, their highest specific tensile strength and modulus in this work can be 600 MPa/(g/cm3) and 31 GPa/(g/cm3), respectively. These properties not only can be comparable to carbon-/glass-/aramid-fiber-reinforced thermoset or thermoplastic polymers (CFRPs, CFRTPs, GFRPs, GFRTPs, AFRPs, AFRTPs), but also the PFRPs can exhibit outperforming ductility (specific strain at peak load ˜ 4 %/(g/cm3)) compared to other composites. This work aims to contribute to advancing fully-recyclable thermoplastic PFRPs for their potential applications in automotive, aerospace, and various other industries