Bubble formation and transport in T-junction for application to Liquid Composite Molding: Wetting effect

Abstract

The aim of this work is to underline the influence of the wetting behavior on bubble formation and transport during the impregnation of fibrous preforms for Liquid Composite Molding processes. The void prediction within the elaboration of composite material sparks off interest because it represents a significant issue to keep the expected mechanical properties of the final product. Voids or bubbles are mainly formed due to the resin flow competition inside and outside the tows. However, the experimental characterization of void formation and transport during the flow inside fibrous media remains delicate. Since the direct visualization of the liquid flow and the entrapped bubbles in a practical material is uneasy, we used model networks to study the formation of bubbles and their transport. Thus, our experimental study deals with a simple configuration of connected pores: two capillaries converging at a node perpendicularly (T-junction). We emphasized on microfluidic and millifluidic approaches where the wetting is significant during bubble formation mechanisms. For the same flow conditions, the experimental results reveal that the bubble lengths are higher for partially wetting liquids than for completely wetting ones. In a wetting case, it was demonstrated that the lubrication hypothesis can be a good approximation to describe the bubble transport in fibrous media.