Liquid Composite Molding
“Liquid composite molding comprises all the composite manufacturing methods, where the liquid state matrix material (e.g. epoxy resin) is forced into the dry preformed reinforcing material (e.g. carbon fiber fabric). The main objective is to reach a full impregnation as the resin propagates between the fiber bundles and fibers. The impregnation driving force is usually resulting from pressure difference. Resin transfer molding (RTM) utilizes positive operating pressures, while in vacuum infusion the pressure is lower than the atmospheric pressure level. Vaccum assisted resin transfer molding (VARTM) operates with positive injection pressures, while the mold cavity is kept under vacuum. Positive operating pressure techniques require matched molding (two or more part molds), while vacuum infusion is usually done using a flexible membrane (e.g. polymer foil) on the mold.” (Simon, Aerospace and Advanced Composites, 7/14/2011)
Recent US Patents
9/27/2011
8,025,834
Process and apparatus for molding continuous-fiber composite articles
Miller, Bailey and Rosario, Jr. of Lockheed Martin, Maryland, developed a device for multi-shot, liquid-resin-molding of continuous-fiber composite articles. The process involves the step-wise fabrication of an article wherein continuity of the fibers is maintained between the multiple workpieces of the finished composite article. (RDC 9/29/2011)
1/4/2011
7,862,322
Resin infusion between double flexible tooling system
Okali and Lim of Florida State University, Florida, have developed a resin infusion system uses a housing that has an upper flexible diaphragm and a lower flexible diaphragm such that the two diaphragms form a cavity. A fiber reinforcement mat is positioned within the cavity. A mold is positioned below the lower diaphragm. A flow plate has a series of V-shaped grooves and is positioned either underneath the lower diaphragm or overtop the upper diaphragm so that the grooves press into the respective diaphragm. A vacuum is created within the housing causing resin to be drawn into the cavity with the resin interacting with the grooves increasing the turbulence of the resin flow. Once the reinforcement mat is properly wetted, the mold is pressed into the lower diaphragm. (RDC 7/13/2011)