Flexural behavior of an FRP sandwich system with glass-fiber skins and a phenolic core at elevated in-service temperature

This paper presents the effects of elevated in-service temperature on the flexural behavior of sandwich composites consisting of glass-fiber-reinforced-polymer (GFRP) skins and a phenolic core. The glass transition temperatures of the GFRP skin and phenolic core were obtained from dynamic mechanical analysis (DMA). Subsequently, the flexural behavior of the GFRP skin and the sandwich beams were assessed with a 3-point static bending test at temperatures ranging from room temperature up to 180 °C. The results show that the variation trend of the GFRP skin's stiffness from 3-point static bending test is in general agreement with the corresponding storage modulus results from the DMA. The GFRP skin, phenolic core, and sandwich beams retained more than 80% of their mechanical properties at 80 °C. Moreover, the flexural behavior of the sandwich beams was governed by the GFRP skins up to 80 °C, while the phenolic core played a major part on overall behavior beyond this temperature. The full-composite action between the skin and core was lost due to the disintegration of the phenolic core at high temperature.