A porous capillary tube approach for textile saturation

Capillary-driven saturation of the reinforcing structure is an important aspect of liquid composite molding processes. Interacting with the flow-induced saturation, process speed must be optimized to guarantee full wetting while being time-efficient. The well-known Lucas-Washburn equation gives an estimate of the capillary imbibition in porous materials but lacks accuracy in case of textile structures. In this work, capillary rise experiments of different glass and carbon reinforcements are compared. An extension to the Lucas-Washburn equation is proposed based on regression-based fitting and validated with the experimental results. It considers peripheral flow in the textile as well as gravitational effects. Good conformity could be shown for textiles with many cross-sections. Unidirectional, low fiber volume content and irregular-shaped fabrics are more difficult to handle. The accurate determination of the capillary radius and the peripheral fluid flow are key factors.