Influence of moderate/high temperatures on the residual flexural behavior of pultruded GFRP

Abstract

This work aims to investigate the influence of the exposure to moderate/high temperatures on the residual flexural properties of commercial pultruded profiles of glass fiber-reinforced polymer (GFRP) composite having different formulations. The experimental program included flexural and interlaminar shear tests for four different GFRP formulations at room temperature and after exposure to temperatures up to 320 °C. To investigate the materials’ thermal stability, thermogravimetric analyses (TGA) were performed and dynamic mechanical analyses (DMA) were carried out to evaluate the changes in the glass transition temperature. Scanning electron microscopy (SEM) and x-ray microtomography techniques were also used to analyze the microstructure and the damages after exposure to temperature. The results from bending tests showed that all but polyester-based composites showed a slight increase of modulus for intermediate temperatures, followed by a decrease as it approached the degradation temperature. All specimens failed in interlaminar shear due to porous interface between layers and a large deviation was obtained for the strength. For interlaminar shear properties also seemed to be influenced by the competing effects of post-curing and matrix degradation. For this latter test, vinyl ester matrix composite had the best performance whereas the polyester matrix composite had the lowest.