Experimental investigation and numerical modeling using Halpin–Tsai equations and classical laminate theory on the mechanical performance of pineapple leaf/sisal hybrid fiber‐reinforced epoxy composites

Lightweight natural fiber composites are showing promise as environmentally friendly substitutes for glass and carbon fiber‐reinforced systems for semi‐structural automotive and construction applications. The mechanical performance and numerical predictability of 60:40 pineapple leaf fiber (PALF)/sisal hybrid epoxy composites made by compression molding with 5% NaOH‐treated fibers at 0°, 30°, and 40° orientations are assessed in this work. With maximum tensile, compressive, and flexural loads of 3.61 ± 0.12, 3.70 ± 0.18, and 1.67 ± 0.09 kN, respectively, the hybrid composite performed better than single‐fiber systems. Because of fewer gaps and better fiber–matrix interaction, water absorption testing (ASTM D570) revealed 8%–18% lower moisture uptake than individual PALF and sisal composites. The Rule of Mixtures predicted a longitudinal modulus of 26.1 GPa (3.7% departure from the experimental 27 GPa), the Halpin–Tsai model predicted a transverse Young's modulus ( E 2 ) of 9.89 GPa, consistent with reported transverse modulus ranges for natural fiber composites, and Classical Laminate Theory predicted an effective modulus of approximately 27 GPa for the balanced hybrid laminate, in excellent agreement with experimental data. These micromechanical predictions demonstrated good agreement with experimental results. The 30°/40° orientation was shown to be the optimal design for balanced stiffness using TOPSIS optimization. Fiber pull‐out and interfacial debonding were verified as the main failure mechanisms by field emission scanning electron microscopy (FESEM) investigation. For lightweight semi‐structural applications, the developed PALF/sisal/epoxy hybrids show great promise.