Epoxy Reinforced Flax Fibre Composites for Interior Lining Panels of an Aircraft: Flammability Study

ABSTRACT The growing demand for sustainable and lightweight materials in the aerospace industry has prompted significant research into bio‐based composites for interior applications. This study investigates the flammability behaviour of epoxy‐reinforced flax fibre composites intended for use as interior lining panels in aircraft. Two different flame retardant (FR) treatments—designated FR A and FR B—were applied to the flax fibre composites, and their flammability studies, including vertical burn tests (AITM2‐0002), smoke density measurements (FAR‐25 Airworthiness Standards), toxicity analysis (AITM2‐0005), and heat release assessment (AITM2‐0006), were conducted. The results showed that all test specimens met the burn length requirements, with flame‐retardant‐treated samples exhibiting slightly reduced flammability. However, both treated and untreated composites exceeded the allowable smoke density limits, and all specimens produced peak heat release rates higher than the 65 kW/m 2 threshold defined by FAR 25.853. Toxic gas analysis indicated reduced emissions of carbon monoxide (CO), nitrous gases (NOx), and sulphur dioxide (SO₂), with HCN, HF and HCl remaining at minimal levels across all samples. These values were benchmarked against established safety standards such as BSS 7239 and ISO 19700, confirming their compliance with acceptable toxicity thresholds. These findings suggest that while flax fibre composites demonstrate potential as a sustainable alternative for non‐structural aircraft interior components, further optimisation of flame‐retardant formulations is necessary to mitigate smoke generation and heat release. Addressing these challenges could enhance the viability of natural fibre composites in aerospace applications, contributing to the industry's sustainability efforts.