Development of porous biocarbon from passion fruit husk and pearl millet biomass microfiber reinforced epoxy composites

This research investigates the influence of pearl millet husk microfiber and porous biocarbon incorporation into an epoxy resin matrix on the mechanical, thermal, dielectric, EMI shielding, and flammability behavior of the resulting composites. The results indicate that the addition of natural fiber and biocarbon modifies the functional performance of the epoxy system depending on filler composition. Among the variants, EPB1 exhibited the most favorable dielectric response with a permittivity of 4.4 and dielectric loss of 0.77, indicating improved energy storage and dissipation capability compared to neat epoxy. The composite EPB2, containing 56 vol.% epoxy, 40 vol.% pearl millet husk microfiber, and 4 vol.% porous biocarbon, showed enhanced thermal and flame-retardant behavior, with a thermogravimetric mass retention of 96%, a UL-94 V-0 rating, and a minimum flame spread rate of 5.31 mm/min. The overall findings demonstrate that filler content plays a critical role in controlling thermal stability, dielectric response, and fire resistance, while mechanical improvements depend on optimized phase interaction. This work highlights the potential of agricultural waste–based fillers for multifunctional epoxy composites with balanced thermal, electrical, and fire-safety characteristics.