섬유강화 고분자 복합재료의 압축성형에서 성형품의 표면상태에 관한 연구

Abstract

The present study investigated experimentally how defects on the surface of rib molded products developed in the compression molding process of fiber reinforced polymer composite materials have an effect on molding conditions and material characteristics. Particularly, defects formation process after an charge mold cycle are technically described in details. Main findings obtained from experimental investigations are summarized as: For all materials investigated in the present study including Polypropylene(PP), Polystyrene(PS), and X-sheet(XS 40wt%), the measured molding warpage was reduced with increases in the mold releasing temperature while the measured molding shrinkage was increased. The behavior of each of materials was found to vary with the molding load. For Polypropylene(PP) and Polystyrene(PS), the was observed to protrude in the opposite direction. The empirical relationship that can be used to determine the molding shrinkage, molding warpage, and maximum roughness using the mold releasing temperature and molding load was proposed as part of this study. The measured molding shrinkage and molding warpage of the X-sheet(XS 40wt%) were larger compared to those of single material (PP, PS) independent of molding conditions for both molding and cooling process. For rib molded products made of X-sheet(XS 40wt%), heterogeneity effects became dominant due to the anisotropy of fibers and parent materials caused by charge process. The dimensional accuracy for the rib molded products made of Polystyrene(PS) was found to be closely associated with the mold releasing temperature rather than the molding load and the effect of the rib thickness. A small change in dimensional shrinkage of the rib molded products was observed as the mold releasing temperature approaches the material solidification temperature. Increases in the molding load and reductions in the mold releasing temperature during the molding and cooling process were found to suppress the shrinkage in the width dimension for Polypropylene(PP) and Polystyrene(PS) rib molded products, lowering the surface roughness for the X-sheet(XS 40wt%).