The implications of fiber compaction and saturation on fully coupled VARTM simulation

Abstract

Vacuum Assisted Resin Transfer Molding (VARTM) is a process by which resin is drawn through fiber preforms in a one-sided mold using an induced pressure gradient. Although the approach to model flow in VARTM is similar to the Resin Transfer Molding (RTM) process, modeling in VARTM can be significantly more complex if one accounts for fiber compaction and the dual scale nature of the fiber preform which is present in RTM but often neglected. This article investigates the influence of fiber compaction and fiber tow saturation during mold filling in the VARTM process. A non-rigid control volume is used to formulate a set of governing equations to describe the resin flow. Tow impregnation at the micro-scale is coupled with global resin flow at the macroscale by applying conservation of mass principles. Preform compaction is modeled as a non-linear spring bed where compaction pressure is dynamically distributed between the resin and the preform. The variation in preform permeability is modified due to the changes in the fiber volume fraction as a result of changing compaction. A simple one-dimensional mold filling case is solved to investigate the role of compaction and dual scale porous media in VARTM processes. A parametric study allows us to identify situations in which one can neglect compaction and saturation and conditions under which a fully coupled model should be applied for satisfactory results.