Advanced modeling and simulation of sheet moulding compound (SMC) processes

In SMC processes, a charge of a composite material, which typically consists of a matrix composed of an unsaturated polyester or vinylester, reinforced with chopped glass fibres or carbon fi bre bundles and fillers, is placed on the bottom half of the preheated mould. The charge usually covers 30 to 90% of the total area. The upper half of the mould is closed rapidly at a speed of about 40 mm/s. This rapid movement causes the charge to flow inside the cavity. The reinforcing fibres are carried by the resin and experience a change of confi guration during the flow. This strongly influences the mechanical properties of the final part. Several issues compromises its efficient numerical simulation, among them: (i) the modeling of flow kinematics able to induce eventual fibres/resin segregation, (ii) the con ned fibres orientation evolution and its accurate prediction, (iii) local dilution effects, (iv) flow bifurcation at junctions and its impact on the fibres orientation state, (v) charge / mould contact and (vi) parametric solutions involving non-interpolative fields.The present paper reports advanced modeling and simulation techniques for circumventing, or at least alleviating, the just referred difficulties

On the multi-scale description of micro-structured fluids composed of aggregating rods

When addressing the flow of concentrated suspensions composed of rods, dense clusters are observed. Thus, the adequate modelling and simulation of such a flow requires addressing the kinematics of these dense clusters and their impact on the flow in which they are immersed. In a former work, we addressed a first modelling framework of these clusters, assumed so dense that they were considered rigid and their kinematics (flow-induced rotation) were totally defined by a symmetric tensor c with unit trace representing the cluster conformation. Then, the rigid nature of the clusters was relaxed, assuming them deformable, and a model giving the evolution of both the cluster shape and its microstructural orientation descriptor (the so-called shape and orientation tensors) was proposed. This paper compares the predictions coming from those models with finer-scale discrete simulations inspired from molecular dynamics modelling

Orientation kinematics of short fibres in a second-order viscoelastic fluid

Most theoretical fibre suspension models currently used for predicting the flow-induced evolution of microstructure in the processing of reinforced thermoplastics are based on the Jeffery model of dilute suspensions in a Newtonian suspending fluid or phenomenological adaptations of it that account for fibre-fibre interactions. An important assumption of all these models is the Newtonian character of the fluid in which the fibres are suspended. In industrial practice, the considered fluids are in general molten thermoplastics that exhibit a viscoelastic behaviour. Even though few counterparts of the Jeffery theory exist for second-order fluids, they have been rarely considered and, to our knowledge, never taken into account at the macroscopic scale. In this paper, we address the modelling of short fibre suspensions in second-order fluids throughout the different description scales, from microscopic to macroscopic. We propose a simplified modelling framework that allows one to extend to viscoelastic suspending fluids the standard Folgar and Tucker model widely used in industrial simulation software