Boundary element techniques for multiscale filling simulations in dual-scale fibrous reinforcements using two lumped approaches

Non-uniform filling of dual-scale fibrous reinforcements is crucial in modelling and simulation of liquid composites molding processes since this poses several challenges at mesoscopic (void formation) and macroscopic scale (irregular global saturation). This problem is tackled here using two lumped approaches: sink-term and effective-unsaturated permeability lumped functions are obtained from mesoscopic filling simulations, and introduced into Richards and equivalent Darcy equations to conduct macroscopic simulations. Boundary Element Techniques to solve governing equations, a fluid-front-tracking method, a Stokes-Darcy-based methodology to simulate intra-tow liquid absorption considering air compressibility and dissolution, flow-direction dependent capillary pressure, vacuum pressure and dynamic void evolution, are representative contributions of this work. Macroscopic results show that both sink-term and Richards approach are in acceptable agreement with experiments, with former approach providing more accurate results. BEM-based codes are used to study the influence of inlet pressure and flow rate, vacuum pressure, air compressibility and dissolution on the saturation behaviour.