A Semi-Analytical Model to Predict Infusion Time and Reinforcement Thickness in VARTM and SCRIMP Processes.

Felice Rubino,Pierpaolo Carlone

doi:10.3390/polym11010020

Abstract

In liquid composite molding processes, such as resin transfer molding (RTM) and vacuum assisted resin transfer molding (VARTM), the resin is drawn through fiber preforms in a closed mold by an induced pressure gradient. Unlike the RTM, where a rigid mold is employed, in VARTM, a flexible bag is commonly used as the upper-half mold. In this case, fabric deformation can take place during the impregnation process as the resin pressure inside the preform changes, resulting in continuous variations of reinforcement thickness, porosity, and permeability. The proper approach to simulate the resin flow, therefore, requires coupling deformation and pressure field making the process modeling more complex and computationally demanding. The present work proposes an efficient methodology to add the effects of the preform compaction on the resin flow when a deformable porous media is considered. The developed methodology was also applied in the case of Seeman’s Composite Resin Infusion Molding Process (SCRIMP). Numerical outcomes highlighted that preform compaction significantly affects the resin flow and the filling time. In particular, the more compliant the preform, the more time is required to complete the impregnation. On the other hand, in the case of SCRIMP, the results pointed out that the resin flow is mainly ruled by the high permeability network.

Highlights

Advanced composites have encountered a widespread diffusion in different fields, from transportation to sporting goods as well as from energy to infrastructure and architecture, where the need for materials that are at same time stiff and light is constantly growing
The distribution medium induces a through-thickness flow in the preform due to the significant difference in the permeability resulting in a three=dimensional flow front which, as above depicted, advances first through the distribution medium and after within the reinforcement [4,6]. This behavior has to be taken into account when the resin flow in the vacuum-assisted resin transfer molding (VARTM) process is simulated increasing the difficulty in the modelling
Before analyzing the evolution of the flow front, the proposed model was validated with respect to the assessment of the prediction of the preform compaction by comparison with the outcomes provided by Grimsley in [34]

Summary

Introduction

Advanced composites have encountered a widespread diffusion in different fields, from transportation to sporting goods as well as from energy to infrastructure and architecture, where the need for materials that are at same time stiff and light is constantly growing. Preform saturation should be imperatively achieved before the resin reaches the gel point; otherwise, the sharp viscosity increasing will prevent further resin advancement In this regard, an effective strategy to reduce the infusion time relies on the usage of high permeability plastic networks, namely distribution media, which is placed above the nested reinforcement between the peel ply and the vacuum bag. The distribution medium induces a through-thickness flow in the preform due to the significant difference in the permeability resulting in a three=dimensional flow front which, as above depicted, advances first through the distribution medium and after within the reinforcement [4,6] This behavior has to be taken into account when the resin flow in the VARTM process is simulated increasing the difficulty in the modelling. The analysis was performed simulating a simple VARTM process and the SCRIMP process adding the effect of the distribution medium on the reinforcement impregnation

Numerical Model

VARTM Process

Infusion

Conclusions