Tensile, Impact, and Post-Repair Behavior of Self-Reinforced PET Composites: Influence of Service Conditions

Low-velocity impact (LVI) can introduce barely visible damage in fiber-reinforced thermoplastic composites during service, leading to a reduction in structural strength. Although repair strategies are increasingly applied to composite components, the post-impact tensile behavior of repaired thermoplastic composites remains a critical consideration. Accordingly, this study investigates the tensile, impact, post-impact, and post-repair behaviors of self-reinforced polyethylene terephthalate (srPET) composites. Laminates consolidated at 210 °C exhibited a 16% higher tensile strength (93 MPa) and 22% greater strain-to-failure compared to those processed at 220 °C, owing to improved interfacial consolidation and reduced thermal degradation. Temperature-dependent tensile testing showed that specimens tested at −40 °C achieved a 25% increase in elastic modulus and an 18% increase in tensile strength relative to room temperature, whereas testing at 80 °C resulted in a 30% reduction in stiffness due to polymer chain relaxation and matrix softening. LVI testing revealed a clear progression of damage mechanisms with increasing impact energy, transitioning from matrix yielding and fibrillation at 10 J to interfacial debonding, delamination, and fiber fracture at 30–40 J. Residual tensile strength retention exceeded 80% for impact energies up to 20 J, while severe degradation occurred beyond 30 J as fiber-dominated damage and perforation governed failure . Repair of 30 J–perforated specimens demonstrated partial recovery of tensile performance, with low-temperature repair conditions leading to improved strength recovery through enhanced interfacial bonding and fiber bridging within the repaired region. These results demonstrate that srPET composites exhibit favorable damage tolerance, temperature-dependent mechanical performance, and repairability within a mono-material thermoplastic system.