Method of manufacturing y-shaped stringers and double y-shaped spars made of composite material

A method for manufacturing a Y-shaped stringer made of composite material, the Y-shaped stringer comprising a stringer web having a cross-section with an I-shape, lower flanges, a first opened triangular-shaped cross-section structure comprising first and second lower vertices respectively joined to the lower flanges, and an upper vertex connected to a first edge of the stringer web, wherein an assembly of the first opened triangular-shaped cross-section structure and the stringer web form in cross section a Y-shape,

• the method comprising:
• placing composite material on a first mold and on a second mold each comprising a molding curvature having an angle β=360°−α, wherein α is a working angle formed in a joint between the first opened triangular-shaped cross-section structure and the lower flanges, wherein α has a value in a range of 100 degrees to 165 degrees;
• placing composite material on a third mold;
• closing the first mold and the second mold with the third mold to obtain a closed mold assembly that contains a Y-shaped preform;
• and
• curing the Y-shaped preform in the closed mold assembly with an autoclave cycle to form the Y-shaped stringer.