Abstract

Reinforcement/matrix interaction is recognized as a key issue in polymeric composite materials. From the mechanical point of view, being the link between the fibres and the polymer, a proper load transfer is ensured only if a good enough interphase exists. This is particularly critical in carbon fibre (CF) composites since, due to the non-polar characteristics and chemical inertness of carbon, sometimes they exhibit weak interfacial adhesion. In this sense, various surface treatments for CFs are currently being investigated, in order to improve their interaction with the polymeric matrices: wet chemical or electrochemical methods, chemically or physically activated oxidation procedures, application of thin coatings and plasma treatments. This is precisely one of the challenges addressed in the MODCOMP project.

This paper describes part of the work carried out within the mentioned project in order to estimate the improvement of properties that can be achieved through enhancements of the CF/epoxy interphases. The study covers both elastic engineering constants and strengths predictions, and it has been performed using finite element models of RVEs of UD fibres and introducing cohesive elements to take into account the interfacial failure mode. The results obtained allow identifying which range of CF/epoxy interphase properties enhancement should be achieved in order to get significant effects in the composites mechanical response.