Elevated temperature behaviour of carbon fibre-reinforced polymer applied by hand lay-up (M-CFRP) under simultaneous thermal and mechanical loadings: Experimental and analytical investigation

Carbon fibre-reinforced polymer (CFRP), a polymer matrix composite material, has been increasingly used in industry, science, daily use equipment and engineering in recent decades. In civil engineering, when a construction structure reinforced with external bonded CFRP is subjected to fire, both the structure and CFRP reinforcement are concurrently affected by the elevated temperature and mechanical load. In Eurocode, the evolution of the mechanical properties of concrete and steel are described as decreasing with increasing temperature, while the performance of CFRP has not been clearly mentioned. In civil engineering, there are two common types of CFRP: one that is fabricated in a factory before installation (pultruded CFRP) and one that is fabricated on site during the installation with hand lay-up methods. In the literature, several experimental datasets focus on the first type of CFRP considering different aspects, such as performance under different testing conditions, different temperature levels, etc. This paper focuses on the thermo-mechanical performance of the second type of CFRP with a fire application purpose. The material is tested for mechanical performance at temperature levels varying from 20 degrees C to 600 degrees C and for thermal resistance at different tensile stress ratios from 10% to 75% of the material's ultimate tensile stress at ambient temperatures. The results show that the mechanical performance of the tested material decreased as the temperature increased, the ultimate strength decreased by 50% at 350 degrees C, and the Young's modulus only decreased by 30% at 600 degrees C. The results also confirm that the mechanical status has an influence on the thermal performance of the material and vice versa. A new analytical model has been proposed for the thermo-mechanical performance of the tested material and fits well with other experimental data obtained from similar testing conditions. The outcome of the proposed analytical model is applicable to fire design in civil engineering.