Ultra-high interfacial strength of glass fiber/epoxy composites via semi-interpenetrating networks modified rigid-flexible structures

Interface is one of the key factors to determine mechanical properties of glass fiber reinforced polymers (GFRPs), and relates to the efficient transfer and dispersion of stress from polymer to glass fibers. Fabricating rigid-flexible structures on glass fibers is a strategy to establish robust interfaces in GFRPs. However, the rigid components that consist of nanoparticles usually suffers from agglomerating during the process of GFRPs production, leading to low interfacial strength. In this work, we designed novel rigid-flexible structures on glass fibers by sizing method, and focused on preventing rigid components of rigid-flexible structures from agglomerating. Semi-interpenetrating polymer networks (semi-IPNs) as flexible components of rigid-flexible structures could anchor cellulose nanofibers as rigid components by hydrogen bonding to prevent cellulose nanofibers from agglomerating, thus strengthen the penetration of glass fiber and matrix resin. The uniformly dispersed cellulose nanofibers could deflect cracks and improve modulus to balance modulus difference between glass fibers and matrix resin. As a result, interfacial shear strength (IFSS) and transverse fiber bundle tension (TFBT) strength of GFRPs improved from 36.43 MPa to 48.60 MPa, from 34.43 MPa to 49.39 MPa, respectively. This work provides a promising strategy to strengthen the interfacial strength of GFRPs.