Theoretical and Experimental Modelling of Bubble Formation with Connected Capillaries in Liquid Composite Moulding Processes

TL;DR

This paper combines theoretical modeling and experimental validation to understand bubble formation in connected capillaries during liquid composite molding, aiming to predict void entrapment affecting material quality.

Contribution

It introduces a novel combined approach using simple capillary network models and experiments to predict void formation in complex fiber preform geometries.

Findings

Experimental validation of bubble formation in T-junction devices.

Theoretical model successfully predicts microvoid and macrovoid formation.

Flow dynamics influenced by capillary connections and supply mechanisms.

Abstract

The void prediction in LCM processes sparks off interest within the composite material industry because it is a significant issue to keep the expected mechanical properties. The liquid properties, the preform geometry and the flow conditions impact the quantity of void entrapped inside the final product. The complex geometry of the reinforcement due to the arrangement of the bundles and the fibres is a key point to understand and quantify this phenomenon. This paper deals with both simple model networks which can occur inside a fabric representing connected capillaries, so-called "Pore Doublet Model (PDM)". A first is considering two capillaries converging on a node (T-junction) and a second is representing two capillaries interconnected with a supplying principle. These configurations can affect locally the evolution of flow fronts. First, experiments of bubble formed in a T-junction device have been performed and studied. Then a theoretical approach was proposed to forecast microvoid and macrovoid formation, by taking into account a supplying principle and arranged Washburn equation in forced filling.