PURPOSE: To obtain a lightweight product having high productivity, high strength and high rigidity, which can be utilized as members and parts of an aircraft and spacecraft by inserting a pressurizing cylindrical bag into a pipe comprising resin fiber reinforced composite material and heating and pressurizing the pipe from the inside and outside to form a rib and the pipe into a single body.

CONSTITUTION: A cylindrical bag 1 for pressurization is folded inward at a point midway therein to form a front and rear partitions 6, 6 spaced apart a certain interval on the upper part and lower part of the bag respectively, and a vertical side 7a of a rib 7 of resin reinforced composite material such as glass/epoxy, carbon/epoxy is inserted into between the partitions 6, 6'. The bag 1 is inserted into a pipe 8 of resin fiber reinforced composite material, which is heated and pressurized from the inside and outside of the pipe by an autoclave method. As a result, the rib 7 is fused integrally to the pipe 8 so that the rib is formed into a node of the pipe. The node provides sufficient strength enough to prevent deformation of the pipe, so that strength and rigidity of the pipe is improved even if the thickness of the pipe is thin.