In Situ Strain Distribution Measurement of Polyphenylene Sulfide-Aluminum Injection-Molded Direct Joints Using Synchrotron Radiation Microbeam X-ray Diffraction

The joining of dissimilar materials such as resin and metal has been attracting attention as a means of reducing the weight of automobiles. It is necessary to ensure that the dissimilar material joints are sufficiently strong and durable over time for practical use. Additionally, it is necessary to clarify the mechanisms that produce these properties. We fabricated direct joints of glass fiber-reinforced polyphenylene sulfide (GFRP) and unreinforced pure polyphenylene sulfide (PurePPS) that were injection molded onto aluminum (Al) with nanometer-scale surface irregularities. We used synchrotron microbeam X-ray diffraction to visualize the residual strain distribution at the jointed interface in a nondestructive, micrometer-resolution manner. While the GFRP-Al joint has a lower average tensile residual strain than the PurePPS-Al joint, its strain distributions are quite different. The residual strain distribution of the GFRP-Al joint was comparable to the orientation of glass fibers. The change in the strain distribution when tensile loading was applied in the elastic region was measured, indicating that the tensile strain at the jointed interface increased for PurePPS-Al. Our in situ microbeam X-ray diffraction method helps evaluate the strain at the interface, which is related to joint reliability.