Achieving High Strength and Modulus in Bamboo/Glass Fiber Hybrid Composites Enabled by Synergistic Interfacial Design

Hybrid composites combining natural and synthetic fibers offer a pathway to sustainable structural materials, yet their performance is often limited by weak interfacial bonding and mechanical mismatches between constituents. Here, we address these challenges in bamboo/glass fiber hybrid epoxy composites through a sequential alkali and silane surface modification strategy. Alkali treatment removes amorphous lignin and hemicellulose, creating a roughened, cellulose-rich surface; subsequent grafting with (3-aminopropyl) triethoxysilane introduces an amino-functionalized interphase that covalently bonds with the epoxy matrix. This combined treatment increases the tensile strength of bamboo fibers by 51.2% and the interfacial shear strength by 136.6%, reaching values comparable to those of commercial glass fibers. The resulting hybrid composite exhibits a tensile strength of 485 MPa and a flexural modulus of 30.2 GPa, corresponding to improvements of 39.4% and 98.3%, respectively, over the unmodified hybrid system. Dynamic mechanical analysis further confirms an enhanced storage modulus across a wide temperature range. This work demonstrates that rational interfacial design via sequential functionalization offers a viable route to high-performance, lightweight, and structurally stable bamboo/glass fiber hybrid composites for sustainable engineering applications, such as reusable concrete formwork.