Influence of preforming technology on the out-of-plane impregnation behavior of textiles

Various Liquid Composite Molding processes provide out-of-plane impregnation. Thereby, the emerging pressure distribution leads to a hydrodynamic compaction of the fiber structure. A prediction of the behavior of the fiber structure under these conditions is highly complex, due to strong interdependencies between pressure distribution, compaction behavior, and impregnation behavior. In this study possibilities to influence the hydrodynamic behavior of textiles by preforming technology are investigated, by comparing an untreated glass fiber woven textile with sewed, bindered, sheared, and pre-compacted samples of the same material. A novel measurement apparatus, reproducing the conditions during out-of-plane impregnation, is applied for this purpose. It enables out-of-plane permeability determination simultaneous to online compaction monitoring. Sewing accelerates out-of-plane impregnation, while inactivated binder can preserve the available permeability at high injection pressures. The increasing superficial density and the geometrical changes caused by shearing decrease permeability.