Method of manufacturing product having complex shape by using at least one jig and at least one mandrel

A method of manufacturing a product having a complex shape, the method comprising:

• a preparation step of preparing a prepreg sheet and a first cylindrical mandrel around which the prepreg sheet is wound;
• a first rolling step of forming a first stacking surface by winding the prepreg sheet around the first cylindrical mandrel;
• a first heating step of taping and heating the first stacking surface;
• a second mandrel preparation step of removing the tape and locating a second cylindrical mandrel on an outer circumferential surface of the first stacking surface;
• a second rolling step of forming a second stacking surface by winding the first stacking surface and the second cylindrical mandrel with the prepreg sheet;
• a second heating step of taping and heating the second stacking surface;
• and
• a core removal step of removing the first cylindrical mandrel and the second cylindrical mandrel,
• wherein the second rolling step comprises forming a hole between the first stacking surface and the second stacking surface, and
• wherein the second heating step comprises combining the first stacking surface and the second stacking surface to form a combined stacking surface, thereby filling up the hole.