Toughening of Intraply Carbon/Kevlar Hybrids With Nanosilica and Nanoclay: Mode-I and Shear Behavior

This study investigates the influence of nanosilica (NS) and nanoclay (NC) additives on the Mode-I interlaminar fracture toughness (G_IC) and interlaminar shear strength (ILSS) of intraply woven carbon/Kevlar fiber reinforced epoxy (CKFRE) composites. The toughening mechanisms were observed using a scanning electron microscope and an optical microscope. Results show that both nanoparticle type and concentration critically affect interlaminar performance. At optimum loadings, CKFRE/NC composites exhibited up to 19.1% (2 wt%) and 17.2% (4 wt%) increases in G_IC, while CKFRE/NS achieved a 48.4% improvement at 0.5 wt%. ILSS performance followed a similar trend, with enhancements of 21.6% (2 wt% NC) and 25.7% (0.5 wt% NS). These improvements were attributed to synergistic toughening mechanisms, including crack deflection, particle-induced crack pinning, fiber bridging, and enhanced fiber-matrix stress transfer. However, higher nanoparticle concentrations led to agglomeration, resin-rich zones, and a reduction in interfacial bonding efficiency, resulting in deterioration of the properties. The findings highlight optimal concentration ranges of 2–4 wt% NC and 0.5–1 wt% NS, providing valuable design guidelines for next-generation hybrid composites with improved interlaminar properties for aerospace, defense, and automotive applications.