Modeling Void Drainage with Thin Film Dynamics

J.J. Gangloff Jr.[1], W.R. Hwang[2], S.G. Advani[1]
[1]Center for Composite Materials, Department of Mechanical Engineering, University of Delaware, Newark, DE, USA
[2]School of Mechanical Engineering, Gyeongsang National University, Jinju, Gyeongsangnam-do, Korea

Voids in composite materials can lead to degraded structural performance. The following is a study of voids or bubbles in uncured viscous polymer resin during composites processing. The goal is to determine if voids can successfully migrate towards vacuum pathways, coalesce with the pathways, and escape. Inherent to the coalescence process is the drainage and rupture of the resin thin film formed between voids and the resin free surface. COMSOL Multiphysics 4.2 + Microfluidics module is employed for modeling. The model consists of a single spherical void in a cylindrical axisymmetric two-phase domain of resin and air. Results suggest that resin thin film drainage can be successfully modeled as an exponential decay consistent with experimental results. Thin film rupture modeling is limited due to mesh dependency issues. Also, void dynamics is strongly dependent on void body force and surface tension effects as characterized by the Bond number (Bo).