Optimising the elastic constants of Vachellia nilotica, Prosopis juliflora and Vachellia leucophloea/ceramic fillers...

Natural fibre-reinforced polymer composites are increasingly explored for sustainable structural applications but only limited information is available on the mechanical performance of composites reinforced with Vachellia nilotica, Prosopis juliflora and Vachellia leucophloea. This study aims to investigate whether the incorporation of these novel fibres with ceramic fillers can significantly improve the mechanical (elastic and tensile) properties of epoxy composites. The testing samples (15) are fabricated, containing hexagonal boron nitride, alumina and silicon carbide using the hand layup method and tested according to ASTM standards through impulse excitation and tensile testing. A Response Surface Methodology-Box-Behnken design combined with ANOVA / regression analysis is employed, followed by multi-response optimisation using Grey Relational Analysis. The optimal composite containing 4 wt.% Vachellia nilotica fibre with SiC filler exhibits a Young's modulus of 5.49 GPa, shear modulus of 2.18 GPa and tensile strength of 28.7 MPa, with confirmation errors below 5%. The model exhibits good adequacy (R² = 90.08%, Adj. R² = 82.64%) with acceptable predictive capability (Pred. R² = 62.70%) for optimisation. SEM results show that the SiC-filled composite possesses uniform dispersion and strong interfacial bonding, leading to superior mechanical performance. These results demonstrate that the proposed natural fibre hybrid composites provide enhanced stiffness and strength, confirming their suitability for lightweight structural and electrical insulation applications.