Ultrasonic Welding and Friction Drilling Fasteners for Composite Structures

The NAVY seeks a robust and rapid innovative process for joining thermoset composite structures and the repair of damaged composite parts without destroying the adherends.ĀCurrent practical joining technologies used in thermoset composites include: (a) mechanical fastening and (b) adhesive bonding. Holes drilled in the composite associated with the bolted connection involve stress concentrations and fiber breakage, which reduces the overall strength of the structure. The adhesive bonding using mainly epoxy adhesive is labor intensive and requires extensive surface preparation and long curing time. A mixture of bonded and bolted configurations has been found in most repaired composite structures. Given the process-driven initial bond quality and its property evolution under service/environmental conditions, the added strength and stiffness from bonding to a repaired structure has usually been ignored, and only the bolted effect has been included during the design and certification of the repaired structure. To fill in the current technology gap and demonstrate a novel joining technology for connecting thermoset-to-thermoset and thermoplastic-to-thermoplastic composite parts,ĀGlobal Engineering and Materials, Inc. and collaborators propose to develop a hybrid joining technology based on the combination of ultrasonic welding and friction drill fastening. The novelties and key components of the proposed approach include: (1) a performance-informed ultrasonic welding for joining thermoplastic parts with friction drilling fasteners as the crack arrestors; (2) a hybrid joining method for connecting thermoset parts with tailored interfaces via the rational selection of adhesives and thread forms of friction drilling fasteners; (3) combined data-driven and multiphysics models to establish the relation between the process parameters and the performance data; (4) technology demonstration at the part level using tee joints without and with repair and scarf repaired components; and (5) quick selection of process windows to achieve an improved repair of damaged composite parts using the developed simulation tools.ĀA comparative study will be performed for the composite parts joined by the hybrid approach and by the golden standard based on an autoclave.