Fracture behavior and interfacial toughening mechanisms of SiC microfiller–reinforced gossypium/glass–epoxy hybrid composites for automotive structural applications

This study presents an innovative approach to improving the fracture toughness and sustainability of hybrid epoxy composites by synergistically reinforcing Gossypium (cotton) and E-glass fibers with silicon carbide (SiC) microfillers (20-50 μm, 0-15 wt%). Unlike conventional natural fiber composites limited by poor interfacial bonding, this work optimizes the hybrid laminate architecture and filler dispersion to achieve enhanced crack resistance. Composite laminates were fabricated via a controlled hand lay-up and compression molding process, followed by Mode I fracture toughness (GIC) and compact fracture toughness (KIC) testing per ASTM D5528 and D5045 standards using a 30 kN Instron 3365 frame. Results demonstrated that 15 wt% SiC composites attained the highest GIC = 0.82 kJ/m², while 10 wt% SiC achieved the maximum KIC = 1.52 MPa√m, confirming optimal energy dissipation through crack deflection, bridging, and fiber pull-out suppression. SEM fractography revealed uniform filler dispersion and strong interfacial adhesion with minimal voids, validating the improved load transfer and reduced delamination. Compared to unfilled controls, SiC-filled hybrids exhibited a 47% increase in GIC and 38% improvement in KIC, aligning with literature benchmarks for automotive-grade composites. The innovative combination of renewable cotton fibers with high-strength glass and ceramic fillers offers a sustainable, high-toughness material suitable for automotive body panels, undertrays, and interior structures where lightweight and damage tolerance are essential.