Methods for manufacturing curved omega stringers and Z shaped stringers of composite material and for manufacturing a composite material stiffened panel with curvature

A method for manufacturing curved composite material omega stringers, comprising: automatic tape laying-up in an ATL machine, an AFP machine or a FLU machine and automatic cutting of the contour, to achieve a straight preform with reinforcements; flat forming to obtain an omega shape on the straight preform to transform it into a straight omega shaped preform; and curve forming the straight omega shaped preform by placing it in a flexible tool comprising a longitudinally embedded stiff band and a laminate clamping arrangement, the laminate clamping arrangement being located in extreme positions of the flexible tool, the flexible tool being covered by a mechanical closing arrangement, such that a head of the straight omega shaped preform has reinforcements on both extremes, the reinforcements being held by the laminate clamping arrangement during the forming process, and afterwards the straight omega shaped preform is heated and transformed into a curved omega stringer.