Improved simplified approach for the prediction of porosity growth during the curing of composites parts

One of the major defects which may occur during the manufacturing of thermoset fiber reinforced composites is the creation of voids which are known to induce a severe degradation of mechanical performances. The modeling of porosities growth during curing is therefore of primary importance. This work proposes an improved void growth model taking into account the coupling between water diffusion, thermo-mechanical effects and matrix properties evolution, which are the assumed driving factors of the problem. In the idealized framework of the growth of a micro-bubble in a homogeneous surrounding medium, the existence of a boundary layer, taking into account moisture transfer modifications around the bubble, is proposed and added to the classical approach. This semi-analytical model is solved numerically and its predictions are compared to experimental observations on parts cured with different pressure, temperature and initial moisture contents. After identification of a single adjustable parameter, results prove to fit realistically experimental data.