Fusion Bonding of Thermoplastic Composite Missile Structures

The proposed program will develop a recipe for fusion welding thermoplastic composite missile airframe lap joints. Fusion welding is a well established process with a wide variety of choices for inducing heat at the interface for many configurations, except for cylinders. The problem or challenge is not so much the fusion process once the heat and pressure are on the joint as it is the methodology for getting the correct heat and pressure on the lap joint for fusion to occur. The problem is complicated by the presence of tolerances or gaps in the lap joint as well as the high processing temperature for thermoplastics. A combined analytical and experimental program is planned that will demonstrate a methodology for mitigating the gap issue, then achieving the process temperature for fusion at the lap joint interface, with the correct magnitude of radial pressure on the lap joint. Initially thermal and thermo-structural analytical models will be used as a path finder for the approach. But the only way to demonstrate feasibility is to fabricate representative cylinders and implement the process. SDC will work closely with the AMRDEC as well as prime contractor engineers to do this in the Phase I program.