Porosity reduction using optimized flow velocity in Resin Transfer Molding

Liquid Composite Molding (LCM) regroups a number of well known manufacturing techniques of polymer composites based on resin injection through fibrous reinforcements. LCM processes such as RTM (Resin Transfer Molding) have been increasingly used to manufacture parts for a wide range of industrial applications and were shown to be cost effective in the low to medium range of volume production. To improve the performance of these processes, more scientific knowledge of the impregnation phenomena is required. In LCM processing, injection pressure dominates the impregnation of the fibers. In RTM, the formation of macro/micro-voids entrapped between or within the fiber tows is a function of the capillary pressure, the porosity of the fiber bed and the local fluid velocity. The presence of these voids within the laminate is a common source of micro-cracking that reduce short and long term mechanical properties.In this work, an experimental analysis is carried out on different types of fibrous reinforcements to study the optimal impregnation conditions by relating the content of macro/micro-voids to the local capillary number. Finally, a study demonstrating the impact of voids on mechanical properties of composite laminates is carried out.