Fluid-structure interaction analysis on the film wrinkling problem of a film insert molded part

Back-injection of polymeric liquid to preformed films, also known as film insert molding (FIM), provides the surface quality of polymeric parts. The back-injection material is responsible for mechanical and thermal properties of the part, especially such as stiffness and thermal expansion. In the back-injection molding it is important to ensure that the inserted films are not wrinkled by the injection of molten polymers. In this study, FIM was carried out with utilizing polycarbonate/acrylonitrile butadiene styrene (PC/ABS) alloy and polymethyl methacrylate/acrylonitrile butadiene styrene (PMMA/ABS) film. The wrinkling of films was observed by the atomic force microscope (AFM). Numerical simulations were performed to understand the mechanism of the film wrinkling and optimize the processing conditions of FIM for high precision parts by using commercial packages including Hypermesh™, Moldflow™, and COMSOL™. A critical shear rate for the film wrinkling of a center garnish part was determined based on the deformation energy of plate. It was found that the critical shear rate calculated numerically was in good agreement with that of the film insert molded parts. POLYM. ENG. SCI., 2011.