A method of retaining a molded-in insert in a fiber reinforced thermoplastic composite material and forming a high strength mechanical locking mechanism is provided. The method includes fixing a molded-in insert in a mold cavity. The insert has a cylindrical body and at least one circumferential groove formed in the cylindrical body, and has a substantially concave configuration, and the groove has a groove radius of 0.025 inch or greater, and greater than or equal to a groove depth. The method includes introducing a fiber reinforced thermoplastic composite material into the mold cavity and around the molded-in insert, enclosing the mold cavity, heating and compressing the material in the mold cavity to consolidate the material around the molded-in insert and to form a consolidated fiber reinforced thermoplastic composite structure with the molded-in insert, cooling the structure, and removing the structure with the molded-in insert from the mold cavity.