A molecular dynamics study of the effects of silane and cellulose nanocrystals at a glass fiber and epoxy interphase

Due to commonly observed adhesive fracture, the interphase regions between fibers and matrix have often been considered a critical design factor in polymer matrix composites. This study uses molecular dynamics simulation to explore the effects of two modifications at a glass fiber and epoxy interphase by adding a silane sizing and a cellulose nanocrystal particle. The interphase thickness increases by 1 nm and by 3.8 nm, respectively, when silane coating, a combination of silane and a 36-chain cellulose nanocrystal are added. Furthermore, the shear modulus and strength of the interphase increase by around 120% and 415% in the case of silane and by about 70% and 240% in the case of a cellulose nanocrystal. When both cellulose nanocrystal and silane are added at interphase, the shear modulus and strength increase by approximately 125% and 265%, respectively. The cellulose nanocrystal particle is physically absorbed on the glass fiber surface without silane, and it is physically confined in a region created by covalent bonds between silane and epoxy when silane is present. In both cases, a cellulose nanocrystal particle increases the nanoscale roughness at a glass fiber surface, leading to improved shear properties at the interphase.