Conversion of finger millet husk waste as biosilica functional filler for Digitaria ischaemum fibre-epoxy composite: fatigue, creep, and flame retardant behaviour

Abstract

This research delves into the fatigue resistance, creep behaviour, and flammability characteristics of epoxy composites toughened with Digitaria ischaemum fibres and finger millet husk biosilica. The main objective of this research study was to extract novel natural fibre and filler from biomass wastes and examine their influence on the load bearing properties of epoxy-based composite. The study begins with synthesis of reinforcements and fabrication of composite plates, inclusion of finger millet husk biosilica of 1, 3, 5 vol.% and fibre of 30 vol.% by hand layup method. The tests were conducted as per American Society of Testing and Materials (ASTM) standards. The evaluation provided critical insights that the influence of fibre and biosilica improved the fatigue resistance. The composite N3 with 3 vol.% biosilica and 30 vol.% of fibre exhibited higher fatigue cycle count of 24,093 for 30% of ultimate tensile stress (UTS). Similarly, creep results elucidate that the N4 composite designation delivers low creep strain about 0.0108, 0.0132, 0.0154, 0.0248, and 0.045 for time intervals of 2000, 4000, 6000, 8000, and 10,000 s, respectively. Moreover, it is noted that the presence of biosilica reduced the flammability of composites. The N4 composite designation exhibits comparatively low flame propagation speed of 6.8 mm/min with V-0 grade. The ANOVA results concluded that the results obtained are significant with a P value of 2.7e − 8. Based on the results the novel cellulose fibre improved the load bearing effect along with biosilica of 3 vol.%. However, beyond 3 vol.% of biosilica reduced the load bearing properties. The findings underscore the potential of these composites as sustainable, durable, and fire-safe alternatives for applications ranging from structural engineering to automotives, drones, and defence sector.