Development of Low Cost Fuselage Frames by Resin Transfer Molding

This paper presents work on the development of a low cost fuselage C-frame for aircraft primary structure using a Light Resin Transfer Molding (RTM) process. Compared to labor intensive hand layup prepreg technologies, Light RTM offers some substantial advantages by reducing infrastructure requirements such as hydraulic presses or autoclaves. Compared to Prepreg, Light RTM tooling creates two finished surfaces, which is an advantage during installation due to improved dimensional accuracy. The focus of this work was to develop means of achieving high fiber volume fraction structural frames using low cost tooling and a low volume manufacturing strategy. In this case a three piece Light RTM mold was developed using an internal mandrel. To achieve the strength requirements, a combination of crimped and non-crimped fabrics were selected for the reinforcing preform. This made it possible to reduce the number of flat patterns by more than 8 times, saving layup time compared to the prepreg counterpart. The processing parameters were optimized to reduce cycle time. Permeability, in-situ resin cure monitoring and coefficient of thermal expansion tests were used in the numerical simulations. Process induced deformation and resin flow simulations were completed to provide input for the tool design. In addition to all the process improvements, risk mitigation testing was completed to validate the design allowables. This work was a collaborative effort by an integrated product development team consisting of design, stress and materials and processing functions.