Mechanical Behavior and Design of FRP Structural Members at High and Low Service Temperatures

Current design manuals for fiber-reinforced polymer (FRP) structures only allow limited application of FRP in high-temperature environments. However, the residual mechanical properties of FRP composites at high service temperatures should be considered. This paper presents the results of bending tests on FRP coupon specimens at temperatures from 25 to 120°C and of compression tests on FRP components at temperatures from −40 to 90°C. Although the mechanical properties decrease with increasing temperature, they retain residual strength and stiffness at high service temperatures. The influence of subzero temperatures on the mechanical properties is negligible. Additionally, the flexural properties of the coupon specimens and the compressive properties of the components were experimentally investigated after high-normal temperature cycles, which alternated between 45 and 135°C every 12 h. The results show that repeated high-normal temperature cycles have little effect on the mechanical properties. The simultaneous effects of loading and high-temperature environments on FRP structures should be considered during design. Thus, this paper proposes a design method for calculating the loading capacity of FRP members at different temperatures. Experimental data from literature and this study were normalized and compared with the results predicted by this method. As expected, the proposed method provides a lower envelope of experimental data for both strength and modulus. Thus, the design method can conservatively estimate various mechanical properties of FRP structural members under different loading conditions at high service temperatures. Additionally, the method can be conveniently established and applied in design.