Pseudo-ductile carbon/epoxy hybrid composites

Three different unidirectional interlayer hybrid composite configurations comprising different grades of carbon fibre/epoxy prepregs were designed and tested. The design of the hybrid configurations was based on two simple criteria to assure sufficient strength of the higher strain material layer and to avoid unstable delamination at the first fracture of the lower strain material layer. One of the three tested configurations demonstrated a favourable pseudo-ductile failure character along with outstanding initial stiffness and up to 1% pseudo-ductile strain between the first fracture and the final failure. A recently developed representation of the predicted failure sequence in the form of damage mode maps was applied to the tested configurations to understand the observed failure modes better. Good correlation was confirmed between the predictions and the experimental results; therefore the validity and merit of this new design tool was highlighted.