Emerging Liquid Thermoplastic Resin-based Fibrous Composites for Structural Applications: A comparison with conventional Glass/Epoxy

Abstract

Despite offering superior mechanical performance and excellent chemical resistance, thermoset-based fibrous composites come along with a few drawbacks, such as brittle failure, non-biodegradability, difficulty in recycling, and difficulty in joining. These challenges can be addressed by a novel polymer matrix, Liquid Thermoplastic Resin (LTR). Unlike other thermoplastic polymers, LTR offers recyclability, weldability, and easy processing to fabricate composites through Vacuum Assisted Resin Transfer Molding (VARTM) without compromising their mechanical performance. This study focuses on the systematic evaluation of the flexural behaviour of glass/LTR composites compared to conventional glass/epoxy composites at room temperature, aiming to offer a sustainable solution. Before mechanical and thermal characterization, the volume fractions of fibers and voids were determined through a resin burn-off test at 500 °C. The flexural tests revealed that the strength of glass/LTR is significantly higher (~18%) and the flexural modulus is marginally higher (~7%) than that of glass/epoxy composites. More importantly, the strain at the peak of glass/LTR is ~17% higher than glass/epoxy composites, which indicates that the failure is more ductile in the case of glass/LTR composites. In addition to flexural characterization, thermal and thermo-mechanical analysis were also performed for both glass/LTR and glass/epoxy composites by employing differential scanning calorimetry and standard dynamic mechanical thermal analysis techniques. Further, the fractography performed using scanning electron microscopy revealed typical failure modes like fiber pull-out, interfacial debonding, and fiber breakage.