Improving post-fire performance and thermal stability of FRP with silicon-based matrix replacement

The fire and thermal performance of fibre-reinforced polymer (FRP) composites has consistently been ranked as one of the most significant challenges in structural and civil engineering. This paper presents a test program that aims to set the limits of the traditional structural epoxy-based FRP and investigate the feasibility of reusing the fibres after complete matrix decomposition. To address the challenge of the deficient thermal performance of FRP, this work develops a solution through a silicon-based matrix replacement. The improvement of mechanical performance at elevated temperatures is driven predominantly by thermal stability and fibre-matrix compatibility. This paper demonstrates the results of 54 FRP coupons with two different matrices, i.e., commercially available epoxy and high-temperature adhesive/silicon-based matrix (SBM). Furthermore, the results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests were conducted on the carbon fibres with and without the respective matrices in air and oxygen-free environments (pure nitrogen). The behaviour and effectiveness of both FRP schemes are tested after exposure to temperatures up to 800 °C under steady-state conditions. It is revealed that this innovative matrix can provide adequate residual capacity for the FRP scheme up to 500 °C. Additionally, it offers enhanced fire resistance, significantly preventing the spread of fire due to its high thermal stability, showing no evidence of charring or thermal decomposition within the studied temperature range. Unlike conventional polymeric matrices, the proposed SBM is typically used in industrial sealing applications in high-temperature environments, and has not previously been integrated into FRP strengthening systems. The results, therefore, reflected the strong potential for the proposed matrix replacement as an alternative to conventional structural FRP composites and for confinement applications.