Effect of Resin Interlayer on Fracture Behavior of Composite Laminates

In this work, the effect of resin interlayer on the fracture behavior of composite laminates is evaluated. For cracks in elastic laminates, the closed-form solutions for energy release rate and mode ratio are presented. These solutions are applicable to structures where classical laminated plate theory may be used to predict deflections and strain energies. For a typical graphite/epoxy composite laminate containing a free edge delamination bounded by an isotropic resin interlayer, it is found that the energy release rate is not sensitive to the Young's modulus of the resin interlayer, but the mode ratio is very sensitive. However, the energy release rate is insensitive to the Poisson's ratio of the resin interlayer. It is also found that within a certain range, the thickness of the resin interlayer does not have much effect on the energy release rate. The limitations of the current results are the assumption of elastic deformation and the applicability of classical laminated plate theory.