Improving resistance to embedded delaminations by adding CNTs to epoxy in carbon/(epoxy + CNT) composites.

Low-velocity impact on fiber-reinforced polymer (FRP) composites may cause subsurface interface delaminations. In the case of such multiple delaminations, neighboring delaminations may grow and coalesce into larger delamination under post-impact loading. The resistance to such growth is substantially influenced by the strength and stiffness of epoxy resins used in FRP composite laminates. Therefore, the current study attempts to determine how adding carbon nanotubes (CNTs) to epoxy might potentially enhance the resistance to such delaminations. A three-dimensional (3D) finite element analysis has been carried out for laminates having single embedded delamination as well as two neighboring embedded delaminations to determine the interlaminar stresses and strain energy release rate using virtual crack closure integral. Results from the current analysis show that while parameters like shape, size, and relative spacing of delamination influence the growth, however in all the cases, adding CNTs to epoxy significantly improves the resistance to the growth of both single and interacting delaminations. The effect is observed to be more pronounced when the delaminations are closely spaced and tend to coalesce into a large delamination. [ABSTRACT FROM AUTHOR]