failure as well as non-uniformity of a local stress distribution at the
interface. For this purpose, numerous models describing stress distributions
and interfacial failure in fibre–matrix systems were proposed.
Several stress-analysis schemes have been used to assess the energy release
rate G for initiation of an interfacial crack in a microbond specimen.
A comprehensive theory was developed by Nairn et al. [12–14].
The model assumes that the debonding zone extends when the energy
release rate reaches its critical value GIc; thus, GIc is equal to the interfacial
fracture toughness. The value of GIc reflects the energy-dissipation
capacity during the debonding process of fibre–matrix system. Recently,
the model was further modified by Scheer et al. [14] and applied to both
experimental and numerical finite-element (FE) analysis mainly for
glass and Kevlar fibres. In our study, the method will be applied for
the carbon fibre/epoxy system.