Clarification of Void Flow Behavior in Structural Resin Transfer Molding by Coupled Macro-Micro Flow Analysis

Abstract

Coupled macro-micro flow analysis procedure using finite element method was proposed to clarify void flow behavior in structural resin transfer molding (SRTM). It was assumed that macroscopic flow between fiber bundles and microscopic flow within fiber bundle were separatable phenomena, so that both flows were analyzed. First, the macro-flow analysis between fiber bundles was performed. Second, resultant pressure distribution in the macro-flow analysis was given as a boundary condition in the micro-flow analysis, and the micro-flow analysis was performed. Permeabilities onD'Arcy's law were calculated in both analyses. Ratio of the microscopic permeability (Kmicro) to the macroscopic permeability (Kmacro) was defined as the permeability ratio that represents an index to determine whether microscopic voids were formed or not. Various fiber distributions were possible to expressed by combination of the macroscopic models with the microscopic models. A fiber distribution state of random oriented glass fiber reinforced mat was improved by combustion in an oven (heat cleaning), so that molding experiments using these glass fiber mats were carried out. Both the macroscopic and microscopic voids were not observed in the case of heat cleaning, while the microscopic voids remained within fiber bundles in the case of without heat cleaning. This difference in void formation could be explained using the permeability ratio.