Method for producing a stiffener on a surface of an element to be stiffened

A method for forming a stiffener on a surface of an element that is to be made rigid, wherein at least one of the stiffener and the element to be made rigid comprises a composite material that is not completely polymerized, comprising:

• positioning the stiffener and a core on the element to be made rigid, wherein the stiffener comprises in a transverse direction two contact zones with the surface, and between the two contact zones the stiffener and the element to be made rigid form a cavity that is open at at least one end of the stiffener, and wherein the core is positioned in the cavity;
• wherein the core comprises a first part contacting an interior surface of the stiffener and at least one second part contacting an interior surface of the stiffener;
• polymerizing at least one of the stiffener and the element;
• and
• removing the core from the cavity after polymerization;
• wherein the core is removed from the cavity by pulling on one end of the second part, the second part having a configuration and elongation percentage that permit the second part to be withdrawn from the cavity by pulling on one end of the second part so as to cause a decrease in its cross-section, and removing the first part from the cavity after the second part has been removed from the cavity,
• wherein the surface of the element that is to be made rigid has an undercut shape of depth E, and wherein the second part has a thickness of greater than E.