Effect of Reinforcement Type and Epoxy‐to‐Hardener Ratio on the Curing Quality and Mechanical Properties of Epoxy Composites

ABSTRACT The effect of reinforcement type, along with epoxy‐to‐hardener ratio (ER:H), on the curing quality and overall performance of epoxy composites has not yet been adequately established. To address this gap, this study employed a combined methodology of differential scanning calorimetry (DSC) and cure index (CI) analysis to quantitatively assess crosslinking efficiency alongside structural and mechanical properties. Composites were reinforced by nylon mesh, aluminum foil, polyethylene, and jute fiber at ER:H ratios of 8:2 and 7:3. DSC revealed that ER + aluminum (7:3) achieved the highest enthalpy (1049.3 J g −1 ), representing a ~52% increase relative to unreinforced epoxy (695 J g −1 ). CI evaluation confirmed that this formulation attained an “excellent” cure classification, while polymeric and natural reinforcements exhibited poor cure quality. Mechanical testing showed that the elastic modulus improved to 24.1 GPa for ER + aluminum (ER:H = 7:3), and hardness increased by ~22% over epoxy. Furthermore, water absorption resistance was dramatically improved by the reinforcement of aluminum and jute at ER:H = 7:3, showing negligible uptake (< 0.1%). Overall, the integration of DSC and CI provides a rigorous framework to link curing dynamics with multifunctional performance, demonstrating that optimizing the ER:H ratio and reinforcement selection, particularly with aluminum, yields highly cross‐linked, mechanically robust, and moisture‐resistant composites suitable for demanding structural applications.