| 摘要 |
PURPOSE:To facilitate the pulling out of a mandrel main body and to prevent the application of a scratch or the like to the inner wall surface of a molded product by dividing the mandrel main body into a plurality of sections in its longitudinal direction and providing a gradient to the matching surfaces of the respective divided mandrels in the longitudinal direction thereof. CONSTITUTION:A fiber reinforced plastic sheet 3 is wound around the outer peripheral surface of a mandrel main body 1 in an uncured state to be laminated thereto and cured under heating to be molded. Divided mandrels 1a, 1b are pulled out of the molded hollow square material 4 left and right in the longitudinal direction thereof to prepare the fiber reinforced plastic hollow square material 4. Since the mandrel main body 1 is constituted in a divided state and the matching surfaces 2 of the divided mandrels 1a, 1b have a gradient alpha of a predetermined angle, the mandrels 1a, 1b can be simply and easily pulled out by weak force when they are pulled out of the hollow square material 4 left and right in the longitudinal direction thereof without applying scratch to the inner wall surface of the square material 4 by the edge part of the mandrel main body 1. |
