Impact of Stoichiometric Imbalance on the Mechanical and Thermal Properties of Modified Al ₂ O ₃ ‐Carbon Fiber Epoxy Composites: A Combined Experimental and Statistical Study

ABSTRACT Fiber‐reinforced epoxy composites hold significant potential for advanced engineering applications due to their excellent thermal stability, mechanical strength, and reduced weight. In this study, the effects of the epoxy‐to‐hardener stoichiometric ratio and APTES‐modified Al ₂ O ₃ nanoparticles on the thermal and mechanical properties of composites, fabricated using the hand lay‐up method, were investigated. Among the tested formulations, the epoxy‐to‐hardener ratio of 3:1 demonstrated superior thermal, mechanical, and viscoelastic properties compared to the 4:1 ratio. Specifically, the unfilled composite with a 3:1 epoxy to hardener ratio and 1 wt.% Al ₂ O ₃ loading showed notable improvements in tensile strength, flexural strength, and Vickers micro‐hardness by ~45.65%, 79.44%, and 23.87%, respectively. The storage modulus increased by ~32.13% compared to the unfilled composite. Additionally, the degree of curing was enhanced with the addition of the filler, as evidenced by differential scanning calorimetry analysis. The experimental findings were further validated through a one‐way analysis of variance and Grey relational analysis, which showed the best relationship among experiments focusing on optimal experiments with the observed data. These results suggest that the insights and methodologies presented in this study can serve as a foundation for the development of high‐performance composite materials for a wide range of engineering applications.