Parameter identification of elastic interphase properties in fiber composites

The interphase region significantly influences the overall material behaviour of fiber composites as experimental investigations show. Since the interphase performance depends on the manufacturing process, their properties cannot be determined directly from bulk material specimen. Therefore, the elastic properties of the interphase are identified on the basis of a micromechanical model from the experimental data of the effective elasticity parameters of the homogeneous substitute material. By means of the generalised method of cells the average properties of the homogenised materials are related to the material parameters, the volume fractions and the geometrical arrangement of the individual phases. A third constituent besides the ones for fibers and matrix accounts for the interphase in the representative volume element. The model response is fitted best to the data with a gradient-based optimisation strategy, requiring the sensitivity analysis of the micromechanical model.