The purpose of this study was to clarify the relationship between the molding pressure of the autoclave when molding carbon-fiber-reinforced thermoplastics (CFRTP) and the bonding strength between CFRTP and aluminum alloy on the basis of the thermal expansion of CFRTP. A CFRTP plate was molded under arbitrary temperature and pressure conditions using an autoclave, and the CFRTP plate was inserted into a heated aluminum piece and joined. A tensile test was conducted on the joined sample, and the joining strength between CFRTP and the aluminum alloy was evaluated. When the molding pressure of the autoclave was varied from 0.2 to 0.8 MPa and the thickness of the CFRTP plate at each molding pressure was confirmed, it was found that a large drop in the plate thickness was observed at the molding pressures of 0.4 and 0.6 MPa. In addition, cross-sectional observation of CFRTP after autoclave molding and heating was conducted, and the unjoined portion was confirmed. Furthermore, from the observation of the cross section, the aspect ratio of the carbon fiber bundle was calculated. As a result, it was found that there is a relationship between the molding pressure of the autoclave and the joining strength between the heat-expanded CFRTP and the aluminum alloy.
