EVALUATION METHOD OF JOINING STRENGTH OF CFRTP MANUFACTURED BY HYBRID INJECTION MOLDING PROCESS

摘要

Hybrid injection molding is a method which is combined injection molding and hot press molding. This method is possible to produce molding articles of high rigidity, high strength and complication shape. In hybrid injection molding, a thermoplastic CFRP laminated material is heated and press molded into a desired shape by clamping, followed by injection molding of a molten polymer and joining with the laminate. Therefore, it is important to improve the reliability of the joining strength of a molded product formed by hybrid injection molding. In general, the joining strength is evaluated by a tensile shear test. However, in the tensile shear test of CFRP, when the rigidity of the test piece is insufficient with respect to the tensile load, deformation occurs, and the bending moment is considered to influence the stress state of the joint. In addition, when the joining strength exceeds the tensile strength of the injection molded part, the injection molded part is broken. Therefore, it is not applicable to evaluate quantitatively the joining strength. In this study, in order to improve the reliability of the joining strength of the CFRP parts manufactured by hybrid injection molding, the deformation behaviour of the test piece in the tensile shear test is investigated and an appropriate evaluation method using the auxiliary jig is proposed. The test piece was prepared by hybrid injection molding using a CF/PA66 laminate and a short CF/PA66 pellet using a near-infrared heater as a heating device. The deformation behaviour and stress distribution of the specimen in the tensile shear test is investigated by three-dimensional strain distribution measurement. As a result, in the modified method, it was found that the tensile failure at the short CF/PA66 is suppressed and the shear failure can be occurred at the joint.