Thursday, December 14, 2017
Dr. Yujie LIU
Sun Yat-sen University
2:00 - 3:00pm
SEH, B1220
Abstract
Developed in recent years, LCM( Liquid Composite Molding) processes are particularly interesting for the manufacture of large or complex composite aerospace parts. These processes consist in infusing a liquid resin into a stacking of fibrous preforms, on which a mechanical pressure field is applied. However, the inhomogeneous micro-structure of the fiber bed may cause the creation of micro/macro-voids, which can significantly affect the quality of composite parts. To improve process performance, the percentage of voids formed during matrix infiltration must be reduced. A bifluid–solid contact model involving surface tension and wetting effects is thus developed within a finite element framework, in order to provide an accurate characterization of the fluids and fibrous behaviors during LCM processes. This model is based on an Eulerian approach of two immiscible fluid (resin/air) domains with boundary conditions which prescribe wetting phenomena at fluid/fiber interfaces. The fluid interface is described by the Level-Set method, on which capillary force is considered. The resulting resin-air Stokes's equations are solved by using finite elements, linear both in velocity and pressure, stabilized by a variational multiscale method. In the elements crossed by the interface, the discrete pressure field is enriched in order to describe the pressure discontinuity. This framework is assessed with 2D simulations of a droplet spreading. 3D simulations of classic wetting problems are also investigated. Expected numerical results are obtained. Numerical simulations of an impregnation of fibers in the resin has been performed to illustrate this challenging physical problem.
Biography
Dr. Yujie Liu is an associate research fellow at School of Data and Computer Science, Sun Yat-sen University. She received her Master in Mathematical Engineering from Pierre and Marie Curie University (Paris 6) in 2010, and PhD in Applied mathematics from Aix-Marseille University in 2014, respectively. Thereafter, she joined the Department of Mechanics and direct Manufacturing Processes in Ecole des Mines de Saint-Etienne as a postdoc fellow. The research interests of Dr. Liu include development of numerical methods for multiphase flows (incompressible/compressible) and associated interface problems for engineering applications.