Enhancement of resistance to interfacial delamination in carbon/epoxy laminates with part-through-the-width ply break by adding CNTs to adhesive

Part-through-the-width ply break followed by interfacial delamination is a common mode of failure in laminated FRP composites. Resistance to interfacial delamination being a matrix dominated property, the present work investigates the influence of adding CNTs to adhesive resin on the resistance to the delamination at the interface. A laminate with a part-through-the-width broken ply is considered with carbon fiber as the main reinforcement and epoxy mixed with CNTs as the matrix. A full 3D finite element (FE) analysis in conjunction with virtual crack closure integral (VCCI) has been carried out to determine critical strain energy release rate (SERR) as a measure of resistance to delamination growth. Properties of the matrix and the lamina corresponding to different weight percentage of CNTs in epoxy obtained using micromechanics have been used. Results show that addition of a small weight percent of CNTs to the epoxy leads to a significant enhancement of resistance to delamination at the interface of part-through-the-width broken ply and the intact ply and the enhancement is only up to a certain limit of weight percent beyond which the resistance decreases again.