High Performance Carbon Fiber Reinforced Epoxy Composites Modified with Bauxite Residue Particles for Structural Applications

Carbon fiber-reinforced epoxy composites offer high structural performance, but the integration of industrial waste-derived fillers requires systematic assessment of their multifunctional effects. This study evaluates 1–5 wt.% bauxite residue as a secondary filler in continuous CF/EP laminates to establish composition-dependent relationships among mechanical, thermal, and fracture behavior. Carbon fiber content and processing conditions were maintained constant to isolate the influence of filler concentration. Among the investigated formulations, the 4 wt.% composite (C4) exhibited the balanced mechanical and thermal performance, achieving tensile, flexural, impact strengths, and RHN values are191.45 MPa, 194.28 MPa, 43.91 kJ m−2, and 147 respectively. C4 sustained a fatigue stress of 107 MPa at 105 cycles under R = 0.1 and 5 Hz. Through-thickness thermal conductivity decreased from 3.59 to 1.96 W m−1 K−1, while the coefficient of linear thermal expansion decreased from 9.87 × 10−5 to 5.28 × 10−5°C−1 across the investigated compositions. C4 exhibited a heat deflection temperature of 184°C, thermal degradation onset at 315°C, and 39% residual mass at 800°C. SEM examination of C4 revealed fracture features associated with fiber–matrix interaction. The findings demonstrate composition-dependent effects of bauxite residue and support its potential valorization as a secondary functional filler in composites