Mechanical, wear, thermal stability, water absorption behaviour of Cyperus rotundus fiber, and biosilica particle Reinforced epoxy composite

This study presents composite materials made out of epoxy resin along with silane treated Cyperus rotundus fiber at 40 vol.% and silane treated biosilica filler made of Kodo millet husk and tested on mechanical, wear, water absorption and thermal characteristics. The developed composites exhibited significant improvement in overall performance compared to neat epoxy. EB2 showed the highest average mechanical performance, with a tensile strength of 127 MPa, flexural strength of 136 MPa, impact energy of 3.19 J, and hardness of 82 Shore D, which may be attributed to the relatively uniform dispersion of the fiber and filler, contributing to effective stress transfer, reinforcement matrix interaction, and reduced defect formation within the developed composites. Conversely, EB3 showed optimal properties with the lowest specific wear rate of 0.0221 mm 3 /Nm, coefficient of friction of 0.331, and lower water absorption of 1.41% because of increased surface hardness, protective layer formation, lower porosity, and improved barrier properties. Moreover, EB3 is the most thermally stable, with a degradation temperature of 315°C, which may be associated with the increased filler content that restricted polymer chain mobility and promoted char formation. The SEM analysis showed a transition from the smooth brittle fracture surface of neat epoxy to rough and compact fracture surfaces in the reinforced composites, which is consistent with improved reinforcement matrix interaction and increased resistance to crack propagation. Overall, the study has shown that the combined incorporation of Cyperus rotundus fiber and Kodo millet derived biosilica in the epoxy matrix greatly improves the structural and functional performance of the developed composites.