Cavity Pressure Dependence on Tensile-Shear Strength of Metal-Polymer Direct Joining

This work experimentally investigates effects of molding conditions on tensile-shear strength of metal-polymer joining products, of which materials are joined by an IMDJ (Injection Molded Direct Joining) process. The IMDJ process is a particular insert molding using a special metal piece; on the surface of the piece, nano/micro scale structures (holes) are formed. This joining technology has been rarely applied to the real industries; nevertheless the technology has many merits for manufacturing processes. This is because the mechanism of the joining has not been revealed. One of approaches for revealing is to investigate a relationship between molding conditions and strength of the joining, which is the objective of this paper. In this particular work, we utilized aluminum pieces (A5052) and PBT (Polybutylene Terephthalate) materials for joining targets and focused on the pressure in the mold cavity as one of the molding conditions. Since the typical injection molding machine cannot measure and control the cavity pressure directly, a pressure sensor was embedded inside the mold. Time-course behavior of the pressure during molding cannot be represented by one parameter. To change the behavior, we manually controlled two parameters, injection volume and holding pressure, on the injection molding machine by feeding-back the measured value. Additionally, we carried out tensile tests to evaluate the strength of the IMDJ products, which were processed under various conditions. The test applied shear stress at the joining boundary surface to measure the tensile-shear strength of the joining. From the results of the tests, we discuss the effects of the pressure variations on the strength.