Effect of carbon nanotubes on the interlaminar and fracture properties of carbon fiber/epoxy composites

The average properties of carbon fiber reinforced plastics (CFRPs) depend on the extent of interaction between the fiber and matrix. Any means, therefore, to modify either of the two constituents of CFRPs is the key to design the composite. Carbon nanotubes (CNTs) are often used to tailor the interface/interphase in conventional CFRPs either by mixing the nanotubes in matrix or by growing them on the surface of fiber. However, the incorporation of nanotubes, by either means, may affect the mechanical performance of the matrix and that of the composite as a whole. Experiments are carried out to assess the effect of CNT dispersion on the rate sensitivity of matrix, and the effect of CNT grafting on the average mechanical properties of laminated composites. For better dispersion and interfacial interaction of nanotubes with matrix, molecular level designing of nanotubes is carried out by way of functionalization. It is found that the ultimate strength of epoxy composites increases with applied loading rate, and that neat epoxy is more rate sensitive than CNT based epoxy nanocomposites. Significant enhancements are also observed in the interlaminar and fracture properties of CFRPs after the incorporation of grafted nanotubes in the composite.