Thermal and mechanical performance analysis of basalt and glass fiber-reinforced polyurethane-epoxy composites

This study explores the tensile and bending behavior of fiber-reinforced polymer (FRP) composites under a wide range of thermal conditions, focusing on epoxy- and polyurethane-based matrices reinforced with glass (GFRP) and basalt (BFRP) fibers. Comprehensive experiments were conducted at temperatures ranging from −25°C to 400°C to evaluate the mechanical performance and failure mechanisms of these materials. The results demonstrate that epoxy-based composites exhibited superior thermal stability compared to polyurethane-based systems. Among the tested materials, E-BFRP demonstrated the best performance, maintaining 61% of its tensile strength and 79.4% of its bending stress at 400°C. E-GFRP exhibited moderate thermal resistance, whereas polyurethane-based composites, notably PGFRP-K, showed considerable mechanical degradation, with tensile strength reductions exceeding 72% and bending stress losses surpassing 70% under elevated temperatures. Sub-zero temperatures had negligible effects on mechanical properties, but temperatures beyond 250°C induced resin decomposition, fiber pull-out, and diminished fiber-matrix interaction, as confirmed through scanning electron microscopy (SEM). These findings underscore the critical importance of material selection and matrix optimization for FRP composites intended for use in high-temperature environments, providing valuable insights for advancing structural material designs.