Post-fire low velocity impact response of marine grade sandwich composites

Fire resistance is an important issue in marine grade sandwich structures because core materials tend to degrade rapidly following degradation of the facesheet(s) when exposed to fire. This study investigates the impact behavior of E-glass/vinyl ester (VE) balsa wood core sandwich panels subjected to a 1250 °C, 175 kW m−2 flame for 0, 50, 100, and 200 s. The impact response of fire exposed sandwich panels was evaluated under low velocity impact (LVI) using an instrumented drop tower apparatus. The impact response of the sandwich panels was found to decrease as a function of fire exposure. A loss of stiffness associated with fire exposure was found to change the mechanism of impact energy absorption. A greater nominal wood core density was found to provide more structural integrity and impact resistance as fire exposure increases. In the marine grade sandwich panels tested, the total average ‘peak load’, initial stiffness, and propagation energy impact response characteristics were found to reduce by 73, 81, and 54% following 200 s exposure of a 1250 °C, 175 kW m−2 fire, respectively.