In the present work, joining of a carbon fiber-reinforced polymer and dual phase 980 steel was studied using the friction bit joining, adhesive bonding, and weldbonding processes. The friction bit joining process was optimized for the maximum joint strength by varying the process parameters. Then, the adhesive bonding and weld bonding (friction bit joining plus adhesive bonding) processes were further developed. Lap shear tensile and cross-tension testing were used to assess the joint integrity of each process. Fractured specimens were compared for the individual processes. The microstructures in the joining bit ranged from tempered martensite to fully martensite in the cross-section view of friction bit-joined specimens. Additionally, the thermal decomposition temperature of the as-received carbon fiber composite was studied by thermogravimetric analysis. Fourier-transform infrared–attenuated total reflectance spectroscopy and X-ray diffraction measurements showed minimal variations in the absorption peak and diffraction peak patterns, indicating insignificant thermal degradation of the carbon fiber matrix due to friction bit joining.

This research has been clarified the method to precisely analyze characteristics of micro porosity in AZ91D alloy using X-ray computed tomography(XRCT). For analyzing the micro porosity, we used the defect-free sample that had 50 and 100 mm sized artificial holes. The defining of peak in the variation of gray level could be used for analyzing the porosity or compounds. Increasing of image conversion coefficient a, increased the sensitivity of reconstructed image and showed even the difference of matrix. The optimized slice width for measuring the actual dimensions of micro porosity, depends on the size of micro porosity. If the slice width was too thin to analyze only the porosity, even the matrix would be detected as the porosity and the results would include the serious error. The accuracy of data derived from XRCT depends on the slice width related with the amounts of collected data.