Permeability Analysis of Natural and Artificial Fiber Textiles for Liquid Composite Molding Process

In liquid composite molding (LCM) processes a catalyzed resin is forced to flow through a dry fibrous preform, opportunely arranged within a mold. The pressure gradient, positive or negative depending on the particular process, drives the uncured liquid flow at a flow rate which relies on fluid viscosity and preform porosity and permeability. Nowadays, sustainability reasons are pushing the market to the wider usage of natural fibers, such as hemp, jute, flex among others, as an interesting alternative to traditional glass and carbon artificial textiles. This manuscript describes an experimental/numerical approach to analyze the preform permeability and the impregnation flow in the LCM process using different textiles, based on glass, carbon and natural fibers. Unidirectional flow tests were performed using a laboratory scale LCM setup, constituted by a sensed mold in order to dielectrically monitor impregnation and saturation flows. The position of the unsaturated flow front was detected also by means of a camera monitoring the resin flow though milled eyelet sealed using transparent material. The permeability was also numerically inferred using the FlowTex software for all the investigated cases. Numerical and experimental outcomes were finally compared and discussed.