Evaluation of Flow-Mesh Influence in Resin Injection Processes

Abstract

Liquid molding is a versatile composite family of processes largely used in naval and automotive industries. In these processes, a polymeric resin is forced through a mold cavity previously filled with a reinforcement medium. In several cases, the impregnation stage may be too long and, to avoid that a flow-mesh (FM) may be placed over the reinforcement. This FM has very high permeability and high porosity, thus the resin first advances inside it and then impregnates the reinforcement medium. The FM commonly covers the entire reinforcement medium, however this may not the best solution for all situations, since it may produce an irregular resin flow front inside the mold cavity, resulting in void formation or waste of resin. This work performs a study on the most suitable FM length, in relation to the mold length, for rectilinear injections. Main goal is to produce a data set to determine FM length based on mold thickness and in-plane to transverse permeability ratio ($\uppsi ={K}_{xx}/{K}_{zz}$). Results have shown that for common industrial application, where $\uppsi \sim 10$, mold length must be 2.5 times as long as the FM for thick reinforcements. Moreover, for more extreme cases, with $\uppsi \sim 1000$, this value may reach 25.