Influence of thermal post curing on electron beam cured composites

摘要

One of the specific advantages of electron beam induced polymerization is the limited temperature rise during curing, compared to a conventional thermal process, however, the fiber/matrix adhesion in electron beam cured composites is generally lower than in thermally cured thermosets. The absence of high temperature treatment during processing could be responsible for this lack of adhesion. Therefore, the influence of an elevated temperature treatment following the electron beam initiated polymerization of a representative electron beam cured epoxy based formulation was investigated. Both the bulk matrix properties and the interfacial properties of carbon fiber/epoxy matrix composites were examined with Fourier Transform Infra Red spectroscopy, Dynamic Mechanical Analysis, density measurement and micro indentation tests. The effect of postcuring treatment on the bulk matrix depends strongly on the electron beam processing conditions and so on the bulk matrix state before thermal postcuring. The effect of a thermal postcuring treatment on the adhesion between carbon fibers and epoxy matrix was quantified with the micro indentation method and a significant increase of adhesion after thermal postcure was measured in most cases. The relations between electron beam processing conditions (dose, dose per pass), the resulting bulk matrix properties and the effect of the postcuring treatment on adhesion between the epoxy matrix and the carbon fiber are detailed. The relations between fiber/matrix adhesion and bulk properties are not the same before and alter postcuring.