The Interfacial Effect of Structural Optimization of Sugar Palm and Woven Carbon Fiber Reinforced Epoxy Composites on Mechanical, Thermal, Fire Resistance, and Morphological Performance

The pursuit of sustainable, lightweight, and high-performance materials for structural and fire-critical applications has intensified interest in hybridizing natural and synthetic fibers. However, the mechanistic influence of stacking sequence design in sugar palm fiber (SPF)/woven carbon fiber (WCF) hybrid composites remains insufficiently understood. This study systematically examines nine epoxy-based laminate configurations, including five SPF/WCF hybrids (D1–D5) and four reference systems (D6–D9), to elucidate the role of fiber architecture on multifunctional performance. Mechanical testing revealed that the WCF-only laminate (D6) achieved the highest tensile strength (167.5 MPa) and flexural strength (268 MPa), while hybrid designs D1 (WCF/SPF/WCF) and D4 (WCF/SPF/WCF/SPF/WCF) demonstrated superior toughness and impact resistance (61.11 kJ/m2), confirming the ductility contribution of SPF. Dynamic mechanical analysis indicated that D1 retained 90.7% of D6’s storage modulus (17.5 GPa), evidencing efficient energy dissipation. Fire performance under UL-94 standards showed all composites achieved V1 classification, with D1 exhibiting a controlled vertical burning rate (8.12 mm/min), outperforming untreated SPF and neat epoxy. These findings establish stacking sequence as a decisive design parameter governing mechanical integrity, thermal stability, and flame retardancy, positioning SPF/WCF hybrids as viable candidates for sustainable, high-performance applications in structural and fire-sensitive environments.