Characterization of Dual-Scale Fiber Mats for Unsaturated Flow in Liquid Composite Molding

摘要

The drooping inlet-pressure history during 1D filling experiments has been used in the past to detect the onset of the unsaturated flow in certain stitched mats,called dual-scale mats,during mold-filling in liquid composite molding.In this study,one such triaxial stitched mat was tested for unsaturated flow and manifests the characteristic inlet-pressure droop that increases with fiber mat compression.A correlation between the previously proposed dimensionless numbers pore volume ratio(gamma)and sink effect index(psi)and the droop in the inlet pressure history was also sought.By studying the micrographs of the composite samples,gamma and psi were measured for the biaxial and triaxial stitched mats at various states of compression.The observation that the droop in the inlet-pressure profiles increase with an increase in gamma and psi establishes the two dimensionless numbers,along with the presence of straight channels aligned with the flow direction,as good predictors of the unsaturated flow in the dual-scale fiber mats.