Carbon Nanotube Sheet Scrolled Fiber Composite for Enhanced Interfacial Mechanical Properties

Abstract

The high tensile strength of polymer matrix composites (PMC) is derived primarily from the high strength of the carbon fibers embedded in the polymer matrix. Fibers typically have high strength in tension. However, their compressive strength is generally much lower due to the fact that under compression, the fibers tend to fail through micro-buckling (or kinking) well before compressive fracture occurs. One approach to improve properties of the fiber/matrix interface in a PMC is the so-called “fuzzy fiber†concept, where carbon nanotubes (CNT) are grown directly on the carbon fiber through CVD. However, that often leads to degradation of in-plane fiber properties. In our work, we considered multi walled CNT sheets (MWNTS) being wrapped around carbon fiber to improve interfacial properties. In order to understand the effect of CNT sheet orientation on composite strength, an atomistic model was developed to study the interface region between the epoxy (Epon-862), carbon fiber and the scrolled MWNT sheets. Molecular dynamics (MD) simulations were performed on this model using LAMMPS software to study its behavior under shear deformation. After proper equilibration, a uniform shear strain was imposed on the MD model with the appropriate boundary conditions at room temperature. Using a modified formula first proposed by Argon for composites, the compressive strength of the composite was calculated. Shear deformation was applied to the baseline MD model with and without the scrolled CNT sheets, and a similar procedure was followed to obtain the compressive strength for proper comparison as described in the paper.