Long‐term residual properties and durability of glass fiber reinforced polymer composite exposed to alkaline solution and natural weather for a decade

This paper presents a comprehensive analysis of the residual thermal and mechanical properties of pultruded glass fiber reinforced polymer composite bars following a decade of conditioning in an alkaline solution and exposure to natural weather conditions. The study focuses on evaluating the changes in the glass transition temperature ( T g ) of the polymer matrix and its impact on the bar's mechanical performance. The results indicate that the T g retained approximately 94.7% of its initial value, with the decrease attributed to the plasticizing effect of absorbed water. The flexural modulus, flexural strength, and transverse shear strength were found to retain 91.8%, 77.2%, and 97.3% of their original values, respectively. The reductions in strength and stiffness were primarily attributed to a weakening in the bonding between the fibers and the polymer matrix. Fractographic analysis revealed that the failure of the plasticized and softened polymer matrix contributed to the observed reductions in strength. Interestingly, the short beam shear strength remained relatively unchanged, as the diffusion of water into the core of the bars at ambient temperatures had a minimal effect. This slower water diffusion in the core led to insignificant degradation of the short beam shear strength. Highlights GFRP bars were exposed to alkaline solution and natural weather for a decade. The water diffusion was a key factor in determining the residual properties of the GFRP bars. The absorbed water plasticises the polymer matrix in GFRP bars. The mechanical property losses in GFRP bars were associated with changes in the matrix property.