Fire Performance and Flame‐Retardant Behavior of Epoxy Resin Modified With Fly Ash and Aluminum Trihydrate

ABSTRACT Flammability in polymer composites remains a critical challenge, especially in epoxy matrices incorporated with mineral fillers. The study investigated the fundamental interactions occurring within an epoxy, aluminum trihydrate (ATH) and fly ash (FA) composite system during exposure to heat. Specifically, FA was incorporated at 0, 5, 10, 15, and 20 wt.% of total composite mass, either alone or combined with a fixed 40 wt.% ATH loading to evaluate differences in flame‐retardancy characteristics. The behavior of the mixture was characterized using cone calorimeter tests to bridge the gap between filler concentration and fire resistance. Preliminary findings indicate that FA significantly alters the composite's thermal properties by reducing the burn rate. Meanwhile, ATH promotes thermal stability by rendering it non‐flammable, although it degrades at temperatures exceeding 200°C. Incorporating FA with ATH into the epoxy resin matrix noticeably enhanced the material's fire‐retardant properties, with the best performance observed when the FA content exceeded 19%. This work advances fundamental understanding of flame‐retardant mechanisms in epoxy composites, providing insights into the effectiveness of FA and ATH as fire‐retardant additives in aviation‐grade epoxy resin composites.