The performance of fiber reinforced polymer (FRP) composites at high temperatures is a serious concern that needs investigation before the incorporation of these composites into important engineering structures. This article presents an experimental study on the tensile properties of carbon fiber reinforced polymer (CFRP) sheets, hybrid carbon/glass fiber reinforced polymer (C/GFRP) sheets and hybrid carbon/basalt fiber reinforced polymer (C/BFRP) sheets at different temperatures. The specimens of FRP sheets were tested at temperatures ranging from 16 to 200°C, while corresponding dry fiber sheets (without resin impregnation) were tested at 16°C as a reference. The test results show that the tensile strength of carbon fibers in different FRP sheets decreases significantly with increasing temperature, and remains almost stable at an ultimate value (3000 MPa) after the polymer exceeds its glass transition temperature (T _g), which is higher than the tensile strength of the non-impregnated fiber sheets at room temperature. At elevated temperatures, the hybridization of fibers can reduce the scatter of the tensile strengths of CFRP composites. Additionally, the tensile strength of CFRP sheets with different dimensions is significantly different, but size dependence is independent of temperature. Furthermore, elevated temperature also influences the failure modes of FRP composites.

This study describes an experimental investigation of the degradation of the tensile properties of basalt fibers and epoxy-based composites in various corrosive environments, including alkaline, acid, salt and water solutions, and clarifies the corresponding degradation mechanisms. Carbon and glass fibers and their composites are adopted as references. Accelerated experiments were conducted at temperatures of 25℃ and 55℃ and the variation in tensile properties was studied by means of tension testing, mass loss weighing, scanning electron microscope imaging and energy spectrum analysis. The experimental results show that basalt fibers posses relatively strong resistance to water and salt corrosion, moderate resistance to acid corrosion and severe degradation in an alkaline solution. The tensile properties of basalt FRP composites are much better than those of basalt fibers. The degradation mechanism of basalt fibers involves damage by etching in salt, water and alkaline solutions and by change in the chemical composites in an acid solution. The fracture properties of basalt FRP composites are controlled by the failure of corroded interfaces between the fibers and the resin, making the interface the critical factor, rather than the fiber itself.