Electromagnetic interference shielding, mechanical and hydrophobic properties of plum peel biocarbon and nutmeg short fiber-reinforced epoxy composite for antenna application

In this research, epoxy-based composites were prepared and evaluated for their mechanical properties, electromagnetic interference (EMI) shielding effectiveness, and hydrophobic characteristics, specifically targeting antenna applications. The primary reinforcement fibers were isolated from nutmeg husk, while the secondary reinforcement, biocarbon, was extracted from plum peel via pyrolysis. The crystallinity of the biocarbon was analysed using X-ray diffraction (XRD). Both reinforcement materials were surface-treated with a silane-based chemical compound (3-Aminopropyltrimethoxysilane), and eight different composite formulations were developed. Mechanical, EMI shielding, and hydrophobicity tests were conducted in accordance with relevant ASTM standards, highlighting the effects of the surface treatment. Among the composites, the silane-treated ET3 formulation (containing 30 vol. % fiber +1 vol. % biocarbon) achieved the highest tensile strength of 143 MPa, an impact energy absorption of 4.7 J, and a flexural strength of 171 MPa. Failure modes and cross-sectional features of the tensile-tested specimens were examined using scanning electron microscopy (SEM). Meanwhile, the silane-treated ET4 composite (30 vol.% fiber +2 vol.% biocarbon), exhibited the highest surface hardness at 98 Shore-D and demonstrated superior EMI shielding effectiveness, characterized by higher absorption and lower reflection across the E, F, I, and J frequency ranges. Furthermore, the hydrophobic silane coating on the reinforcement materials effectively reduced water diffusion into the composite structure compared to untreated counterparts.