High temperature mechanical properties and failure mechanisms of unidirectional glass fiber reinforced composites: Experimental and theoretical modeling

This study investigates the effect of temperature and fiber orientation angle on the mechanical properties of unidirectional glass fiber reinforced epoxy resin matrix composites. Tensile, flexural, and shear tests were conducted on these composites with fiber orientation angles of 0°, 45°, and 90° at temperatures ranging from 25°C to 125°C. The results show that both strength and modulus decrease significantly with increasing temperature and fiber orientation angle. The sharpest decline in these strengths occurs when the temperature exceeds the glass transition temperature of the epoxy resin matrix. As the fiber orientation angle increases, the failure mode of unidirectional GFRC varies from fiber-dominated to interface-dominated. Based on the force-heat equivalence energy density principle and Tsai-Hill theory, a temperature and fiber orientation angle-dependent tensile strength model was developed, which shows good agreement with the experimental data. The influence factor analysis based on this model indicates that the composite strength at low temperatures and low fiber orientation angles is more sensitive to interfacial shear strength. This model can provide a practical tool for evaluating the high-temperature mechanical performance of glass fiber composites and establishing temperature-dependent failure criteria for unidirectional composite laminae.