Hierarchical toughening in Glass/Epoxy Composites: Synergistic effects of fiber texture scale and rubbery nanofiber interleaves on delamination resistance

This study investigates synergistic toughening in glass/epoxy composites through fiber texture scaling (560-2000 mu m bundles) and NBR/PCL nanofiber interleaves. Coarser textures inherently increased fracture toughness by 95-100 % via fiber bridging and crack-path tortuosity. Nanofiber integration amplified this effect, with coarse-textured nano-modified composites achieving 125 % higher toughness than non-modified counterparts. Key mechanisms included matrix plastic deformation (microvoid formation), enhanced fiber-matrix adhesion (resin-coated fibers), and crack bifurcation. Rising R-curves confirmed progressive energy dissipation, while sawtooth force-displacement patterns revealed intermittent crack arrest at nanofiber-rich zones. SEM analysis showed a transition from brittle failure (smooth interfaces) in non-modified samples to ductile failure (rough, porous morphologies) in nano-modified systems. The macro-nano synergy enabled simultaneous improvements in fracture resistance (GIC up arrow 125 %, GIR up arrow 162 %), peak load (up arrow 48 %), and energy absorption without compromising in-plane properties. These results establish a multi-scale design paradigm for aerospace/automotive composites requiring balanced delamination resistance and structural efficiency.