Die cushion motion has been applied to the forming of ribs of discontinuous carbon-fiber composites with panel forming of continuous carbon fiber composites during press forming. This method has the advantage that only a small die cushion load is necessary to form ribs and the length of discontinuous carbon fiber is not damaged during forming. Basic equipment to form a 100-mm-square and 20-mm-high cup with 4-mm-thick cross ribs was designed and fabricated. As the billet material, a flat plate made of randomly oriented thermoplastic discontinuous carbon fiber tapes of 30 mm length and 10 mm width was prepared. Extrusion of the billet to the rib made the fibers flow in the longitudinal rib direction. By using a billet push pin, whose head has a groove for the rib, strong bending strength of the panel was achieved. By pushing the billet material to the rear surface of the panel, fiber flow from the rib to the panel rear surface was formed at the junction, and strong joining strength between the rib and the panel was obtained.
