On the mode II testing of carbon-fibre polymer composites

In this paper the contribution of friction to the mode II delamination toughness of fibre-reinforced laminates has been assessed. It is shown that the conventional analyses used for the determination of G(IIC) i.e. the compliance method and the corrected beam theory method require correction for friction, and that both of these analysis methods over-state the value of G(IIC). It is shown also that the failure to include friction in the analysis results in a deviation between the values of G(IIC) deduced via the experimental compliance method and the values deduced from corrected beam theory. It is shown that friction corrections are significant, and in the case of a tough matrix composite (APC-2) and a glass-fibre epoxy composite may actually lead to the value of G(IIC) being equivalent to the value G(IC), the mode I fracture toughness.