Synergistic effect of Alkali–Silane treated natural fibers and biomass-derived Si ₃ N ₄ bioceramic fillers on the mechanical and electromagnetic performance of polyester composites

Polyester hybrid composites reinforced with alkali-silane treated Bambus Hampi fibres and Si 3 N 4 bioceramic filler produced from Jowar millet husk for EMI shielding applications are the primary focus of this study’s development and multifunctional characterisation. This study made a composites with 40 vol.% fibre and 0-5 vol.% Si 3 N 4 filler and tested them for electrical, mechanical, and electromagnetic interference (EMI) shielding characteristics. Composites made with treated fibres and filled with bioceramic material outperformed neat polyester by a wide margin. With a tensile strength of 162 MPa, flexural strength of 184 MPa, impact energy of 6.96 J, and hardness of 95 Shore-D, PEB3 containing 3 vol.%Si 3 N 4 demonstrated the best mechanical properties among the invented composites. Filler loading improved the dielectric characteristics, with PEB5 exhibiting the best values for both the dielectric constant (4.52) and the dielectric loss (0.27). At 64.1 dB in the X-band and 68.3 dB in the Ku-band, PEB5 attained the maximum EMI shielding efficacy. The increased shielding efficacy was mainly due to interfacial polarisation, Debye relaxation, conduction loss, and absorption-dominated attenuation, as demonstrated by SEM examination, which also showed strong interfacial bonding and excellent filler dispersion. The results show that these eco-friendly sustainable hybrid composites can be used for advanced EMI shielding applications due to their lightweight and high-performance properties.