Effects of CNT microstructural characteristics on the interfacial enhancement mechanism of carbon fiber reinforced epoxy composites via molecular dynamics simulations

Abstract

Numerous studies have concentrated on improving the mechanical properties of carbon fiber reinforced polymer composite (CFRP) through the modification of carbon fiber (CF) with carbon nanotubes (CNTs). However, most of them were confined to describing experimental phenomena. In this study, molecular dynamics (MD) simulation was used to systematically reveal the effect of CNT nanostructures on the interfacial reinforcement of CF/epoxy. An all-atom modeling method was used to provide a quantitative description of the CF-CNT/polymer interface characteristic structure. Computational results indicate that nanotubes can protect the intra- and intermolecular interactions of epoxy segments from being destroyed, thereby preventing the initiation and propagation of micro-defects during interfacial deterioration. The mechanical competition between the interface and polymer bulk leads to different failure mechanisms, and the strengthened interface region has fewer atoms leaving the equilibrium state during tensile deformation. The insertion of CNTs on the fiber surface, specifically increasing their length, diameter, distribution density, or orientation, can improve interfacial tensile strength (up to +62.11 %) and delay the detachment of epoxy molecules from the CF. Additionally, MD outcomes were verified by synthesizing CNTs onto CF using an electric field-assisted flame synthesis approach, leading to improvement in IFSS (+62.67 %) and ILSS (+27.78 %).