Advanced Fasteners for Low Cost Airframe Assembly and Repair

The Joint Venture of Damona Service Company and the Fastenix Corporation proposes to develop self-locking fasteners for airframe assembly and repair. The design concepts for these self-locking fasteners are well thought-out. A prototype fastener is made and proves the design concept works. In order to claim total success of the product, mathematics and stress models need to be developed to predict the fatique life cycle and stress distibution of the composite/fastener assembly. A series of shock and vibration tests need to be conducted to demonstrate fastener performances.The proposed self-locking fasteners have two major parts per set. These two parts lock each other in the assembly after the pre-determined torque is set. Under shock and vibration, the dynamic interlocking force is higher than the static locking force because of the unique design. In addition, a stopper design is incorporated to prevent the interlocking force from being too high in dynamic condition. The interlocking design ensures that the fastener stays intact even though the fastener may lose preload from the changes of composite thickness. Airframe composite thickness may change due to lightning strikes, thermal expansion, water absorption, etc.These invented fasteners allow for loose tolerance holes, and provide efficient interface for high load transfer. No special tools are required for assembly. Standard thread forms are used on the fasteners. For a self-locking nut design, a conventional bolt may be used. The proposed fasteners requires no special drill tooling or pre-assembly fixtures. All these features will save assembly cost significantly.