These investigations are conducted to develop new fasteners and joining methods to reduce weight and improve fatigue life of aircraft structures. Three major modes of structural failures; fatigue, fretting and stress corrosion are discussed with recommendations for improvement. Stress coining was developed to cold work aircraft structure for fatigue improvement. Standard stress corrosion test blocks have been designed for evaluation of this failure mode. A crown flush rivet configuration has been developed that does not require head shaving after installation. Qualification tests were performed in compliance with MIL-Std-1312 to obtain FAA and military approval. Various new fasteners have been developed for aluminum, graphite-epoxy and titanium structure. These fasteners were designed to be forgiving to the hole in that they will fill and prestress the hole uniformly without being extremely sensitive to hole preparation quality.
