Masashi Yamabe

Design concept for one-piece panel vehicular components in SMC compression molding

Products molded from fiber reinforced material are subject to several problems during the manufacturing process such as sink marks, warpage and short shots. In an earlier work, the authors used finite element analysis to analyze the in-mold flow behavior of sheet molding compound (SMC) during the compression molding process. The analytical results were then verified through experimentation. This report first proposes an explanation for the mechanism generating sink marks in a ribbed product having a simple shape. Based on that understanding of the mechanism, a method for minimizing sink marks has been devised and confirmed through experimentation to be effective. The results of the present work are now being used to establish a molding concept for a one-piece outer panel.

On a Stiffness Model for Origami Folding

An evaluation method for stiffness of origami folding is proposed. As a simple idea to evaluate the stiffness, we may consider a sheet of paper as a rectangular board, and evaluate its elastic deformation. However, when we apply this simple idea to folding of a folded sheet of paper, it contradicts the results of a questionnaire survey. We investigate more details of folding motion of origami, and give a hypothesis that the stiffness of folding motion comes from the intersection points of crease lines, where is the toughest points to fold. Our proposed evaluation method is consistent with the questionnaire survey, and hence useful to evaluate the stiffness of folding.Copyright

Application of Numerical Analysis to One-Piece SMC Panels

Products molded from fiber-reinforced material are subject to several problems during the manufacturing process, such as sink marks, warpage and short shots. In an earlier work the authors used finite element analysis to analyze the in-mold flow behavior of sheet molding compound (SMC) during the compression molding process. In the present work a new analytical procedure has been devised for making a detailed analysis of the flow behavior of SMC during the rib filling process. This procedure employs a combination of flow and deformation analysis techniques, a method that was used in the previous work, and also a newly added flow analysis technique at the stage just prior to the completion of filling. A numerical model has also been devised for the molding process described in the previous report, in which back pressure is applied to minimize sink marks. The model is designed so that the relationship between changes in various molding factors and the resulting severity of sink marks can be analyzed quantitatively. The results of the present work are now being used to establish a molding concept for a one-piece outer panel.

Effect of Asymmetrical Configuration of Rib Parts on Defects of SMC Products( Minor Special Issue on Fiber Reinforced Plastic)

The SMC has been developed as a material for the mass production system using press moulding, but some problems arise due to its heterogeneity caused by fibre orientation. The faults observed in the products, such as the appearance of brittle regions in the resin-rich parts or at the weld lines and the surface sink produced at the convex parts, may be regarded as the moulding problems.The purpose of this study was to prevent the above troubles and to construct the CAD system for SMC press moulding process. The case of the symmetrical configuration with one rib part in full charge was treated in the previous paper. In this paper, the effect of asymmetrical configuration with one or two rib parts was investigated to solve the above problems associated with the flow state through the evaluation of flexural strength determined after observation of the material flow state. The analytical method was established by using a linear incremental finite element method and considering the fibre orientation and heterogenity.It was found that the tendency to go around the rib corner increased with increasing the degree of asymmetry, resulting in the resin rich region at the rib corner and no surface sink. Although the weld line at the opposite side of the rib remained, the reduction of flexural strength became less due to curving of the weld line. The stress analysis after the observation of the flow state supports the above tendency well.