For the realization of mass production by press forming using carbon-fiber-reinforced thermoplastic (CFRTP) sheets, a T-beam which is difficult to form with a metal sheet has been press-formed using unidirectional CFRTP sheets. A center clamp and an edge-trimming die have been adopted to avoid wrinkles and to achieve a trimmed part in one cycle. The sheet shape for each fiber direction in the laminates has been designed in considering of the drawing of fibers during forming. T-beams were successfully formed and the rigidity of the formed beams were examined. Compared with steel and aluminum beams of the same rigidity, the mass of the CFRTP beam ranged from 30 to 67% of those materials for bending rigidity. However, torsion rigidity was insufficient in the formed beam. Press forming using unidirectional CFRTP sheets is applicable to the press forming of various shapes considering of the fiber direction arrangement in the laminates and results in the sufficient rigidity and strength of the products.
With the focus on the forming of a tube with differential wall thickness by the ironing of the inner surface, the interaction of the effects of punch geometry (length of parallel part L P, semiangle α P and clearance C P ) on the formability and forming load is investigated by experimentally consistent finite element analysis. Results of the analysis show that L P and α P significantly affect the forming load, while C P has little effect on the load. The punch with larger L P, or the punch with smaller α P or smaller C P, realizes a higher formability because the slipping of steel tube, which is a result of shape defects, does not occur even if Δμ is small. Furthermore, it is theoretically clarified, through discussions on the forces that suppress/induce the slipping of the tube, that slipping does not occur if a large surface pressure is generated on the parallel part of the punch. Since the surface pressure generated on the parallel part of the punch during tube forming varies depending on α P and the area of the parallel part of the punch varies depending on L P, L P and α P should both be taken into account in designing the punch. On the other hand, C P does not affect the other design factors and can be designed independently.