Studies on reinforced vinyl ester composites subjected to fire and impac

Polymer matrix composites (PMCs) are increasingly exposed to catastrophic events such as fire and dynamic impact as their use in defense, transportation, and civil infrastructure sectors expands. The ability to sustain dynamic impact of PMCs can be adversely affected due to fire exposure, yet there exists limited knowledge of the combined effects of fire and impact. This work investigates (1) fire damage progression and (2) post-fire residual low velocity impact resistance of laminate and sandwich PMCs composed of E-glass fiber, vinyl ester resin, and balsa wood core.;An instrumented small-scale burn-through apparatus was designed and constructed to conduct fire exposure tests on PMCs. Burn-through fire damage in the laminate resulted from the heat transfer, thermal decomposition, and combustion of the vinyl ester resin; initial temperature rate increase (time <1 min) and mass loss rate were 227 °C min-1 and 21.6 g min -1, respectively. The balsa core sandwich composite restricted the average cold face surface temperature to less than 150 °C while being exposed to an 80 kW m-2, 800 °C fire for 30 min. On the basis of infrared thermography and quantitative microscopy, a 10-18% difference in cell diameter and 9-10% difference in cell volume fraction of balsa wood resulted in an 8% difference in cold face surface temperature after 30 min of fire exposure. The experimental results were explained by the Gibson thermal model, which predicts cold face temperature versus fire exposure time.;Low velocity impact of the PMCs revealed a reduction in contact stiffness and penetration resistance as a function of fire exposure time. Specifically, the post-fire contact stiffness of laminate and sandwich composites during incipient impact were found to decrease 30% and 65-75% after 100 s of fire exposure, respectively. The post-fire impact resistance evaluated in terms of peak load to cause penetration was found to decrease 39-43% after 100 s of fire exposure. Incipient damage of PMCs during low velocity impact tests correlated well with a classical plate impact model combined with a fire degradation mechanical property model. These overall findings establish correlations and guidelines between certain fire parameters and the resulting impact response of PMCs.