Quantitative analysis of the micro-indentation behaviour of fibre-reinforced composites: development and validation of an analytical model

A shear-lag model has been developed in order to assess interfacial shear strength from micro-indentation experiments. The treatment of the experimental load/displacement curves is based upon the quantification of the two components of the indenter displacement, i.e. (i) the elasto-plastic indentation of the fibre surface by the Vickers indenter, and (ii) the displacement of the fibre surface due to its compression and to the deflection of the matrix. The latter component has been modelled by using an analytical shear-lag model which takes into account both fibre/matrix debonding and fibre sliding in the debonded areas. Some of the basic hypothesis of this analytical approach have been checked by finite-element (FE) simulations with appropriate model configurations. By means of this model, the critical shear debonding stress can be obtained from the experimental indentation curves. Moreover, the data-reduction scheme takes into account separately the local environment of each indented fibre. This method has been successfully applied to experimental data by using a unidirectional E-glass/epoxy composite.