Fie performance of sandwich composites with intumescent mat protection: Evolving thermal insulation, post-fire performance and rail industry testing

In this study, a novel approach to improving the fire performance of sandwich composites without effect on intrinsic composite structure was explored. The intumescent mat M10 and M20 with expansion ratio 10:1 and 20:1, respectively, were used to protect sandwich composite with evaluation for thermal insulation, heat release rate, smoke density, smoke toxicity, and post-fire performance. Due to char layer formed with expanded graphite when intumescent mat exposed to fire, significant reduction in the maximum average rate of heat emission (MARHE), specific optical density and Valeur Obscurcissement Fumée values in the initial 4 min (VOF4) were observed for sandwich composite with intumescent mat protection, which also improved mechanical properties retention following exposure to flame. According to the EN 45545 standard, all composites passed HL3 hazard level of smoke toxicity. However, due to higher expansion ratio, sandwich composites with M20 mat passed HL3 hazard level of MARHE and HL2 for specific optical density. As such, the M20 mat with excellent flame retardant performance and mechanical properties retention could be potentially used for rail industry applications.