Surface-modified canabo fiber/vinyl ester hybrid composites reinforced with macadamia shell biocarbon and copper ferrite nanoparticles for multifunctional EMI shielding applications

Abstract

The increasing use of high-frequency electronic and communication devices has intensified the demand for lightweight, sustainable, and multifunctional materials capable of mitigating electromagnetic interference (EMI) while maintaining excellent structural performance. In this study, alkali–silane modified Canabo fiber reinforced vinyl ester hybrid composites containing macadamia shell-derived biocarbon and copper ferrite nanoparticles were developed to achieve superior electromagnetic shielding, mechanical integrity, thermal conductivity, dielectric response, and magnetic characteristics. Prior to composite fabrication, the Canabo fibers were treated with sodium hydroxide (NaOH) followed by surface functionalization using 3-aminopropyltrimethoxysilane (APTMS) to improve fiber–matrix interfacial adhesion, while the hybrid fillers were also silane functionalized to promote homogeneous dispersion within the vinyl ester matrix. Composite laminates were fabricated using the hand lay-up technique with a constant 40 vol.% Canabo fiber content and varying concentrations of hybrid fillers. Mechanical characterization demonstrated that composite M12 exhibited the optimum structural performance, attaining a tensile strength of approximately 152 MPa, flexural strength of 206 MPa, impact toughness of 6.1 J, and hardness of 92 Shore D owing to efficient stress transfer and enhanced interfacial bonding achieved through the combined alkali–silane surface treatment. Increasing the hybrid filler concentration improved the multifunctional properties, with composite M14 exhibiting a thermal conductivity of approximately 0.48 W m -1  K -1 , dielectric constant of 5.5, dielectric loss factor of 0.29, and enhanced magnetic permeability resulting from the synergistic interaction between conductive biocarbon and magnetic copper ferrite nanoparticles. The maximum total EMI shielding effectiveness reached approximately 51 dB at 20 GHz, where absorption was identified as the dominant shielding mechanism due to the combined effects of interfacial polarization, magnetic loss, conductive network formation, and multiple internal reflections. The developed hybrid composites demonstrated an excellent balance between structural strength and electromagnetic attenuation, making them promising candidates for lightweight electronic enclosures, telecommunication devices, aerospace structures, and automotive electromagnetic shielding applications.