Design and process integration for low cost manufacturing

Between 1998 and late 2000, Lockheed Martin Aeronautics Company conceived, designed, tooled, and fabricated a unitized, fastenerless, all-composite vertical fail using resin transfer molding. The structure was a full-scale component sized for realistic fighter aircraft requirements. Skins were complex mixtures of very lightly impregnated fabric and fully impregnated unidirectional broadgoods. Understructure was formed from an array of complexly configured, dry-braided torque tubes. Costs were collected, analyzed, and compared against the conventional approach, where design and construction of a vertical fail requires mechanical fastening together of pre-cured skins and numerous understructure details. The project produced three high quality fastenerless assemblies produced by resin transfer molding. It also validated a cost savings of 61% and a weight savings of 12% from the conventional approach. At its annual national conference in September 2001, the Composite Fabricators Association recognized this achievement with its Process Innovation Award. This article describes some aspects of the project, with emphasis on the rheological characterization work necessary to support process model studies used to select the optimum injection sequences and process parameters.