金属補強部品と一体成形された樹脂成形品の構造強度

抄録

Failure under a static load was studied for a plastic part which included a metal reinforcement. The metal part was inserted into the mold prior to the injection molding process. The short-glass fiber reinforced PA 66 was then injected into the mold. It was observed in a fracture test that the plastic part was separated from the metal insert at the failure site. Since the contact state between the plastic and the metal was difficult to be experimentally examined, finite element analysis was utilized. The plastic and the metal were considered as two separated structures in the analysis. The boundary conditions were applied so that force was carried across the boundary only if the boundary was closed. To verify the analysis results, the strains in the plastic part were measured at locations near the failure site. It was deduced from the comparison of the analysis with the experiment that the separation of the plastic from the metal at a portion of the boundary yielded stress concentration at the closed portion of the boundary. It was also deduced that this stress concentration induced local plastic deformation of the polymer. It has been clarified that the separation of the plastic part from the metal part is the primary failure mechanism of the plastic part. It has also been clarified that the plasticity of the polymer affects the fracture load of the part.