Process and device for welding a thermoplastic stiffener

A device for statically welding a stiffener to a receiving surface of a skin where both the stiffener and the skin are made of a thermoplastic composite material, the stiffener comprising a stiffener foot having a bearing surface parallel to a portion of said receiving surface and a stiffener flange projecting away from said portion of the bearing surface, said device comprising:

• a metallic support including:
• a seating surface substantially matching the shape of the receiving side of the skin:
• a groove sufficiently large so as to encompass said stiffener flange when said flange is located in said groove;
• and
• a thermal insulator located in and flush with said seating surface and extending over at least a portion of said bearing surface of said stiffener when said stiffener flange is located in said groove;
• a conformal panel and means for applying pressure to said skin forcing at least a portion of said receiving surface into contact with a portion of said bearing surface over at least a portion of said insulator;
• and
• heating means for heating at least said contacting portion of said receiving surface and said bearing surface to a temperature above the melting point of said thermoplastic material.

A method for statically welding a stiffener to a skin using the device of claim 11, where both the stiffener and the skin are made of a thermoplastic composite material, the stiffener comprising a stiffener foot having a bearing surface parallel to a portion of said receiving surface and a stiffener flange projecting away from said portion of said bearing surface, and said welding process welds a portion of said bearing surface to said receiving, and thermoplastic polymer forming the matrix of the stiffener and the skin has a melting point and a glass transition temperature, said method comprising the steps of:

• placing said stiffener on said metallic support with a portion of the stiffener foot overlying a portion of the thermal insulator and the stiffener flange extending into said groove;
• placing the skin on the metallic support with the receiving surface in contact with at least a portion of said bearing surface and located over said thermal insulator;
• placing the conformal panel on the skin;
• applying pressure to the conformal panel;
• actuating the heating means while maintaining the pressure on the conformal panel until the melting point of the thermoplastic polymer is reached;
• turning off the heating means while still applying pressure to the conformal panel;
• and
• releasing the pressure on the conformal panel when the temperature of the foot of the stiffener is lower than the glass transition temperature of the thermoplastic polymer forming the matrix of the stiffener.