The Development of a Durability & Damage Tolerance Qualification Methodology for Military Rotorcraft

The U.S. rotorcraft industry extensively utilizes composites in dynamic structures such as airframe and rotors. Currently, methods of certification involve several sub-element tests leading up to full-scale component testing. In an effort to reduce the cost and development time related to sub-element testing, the Army is actively pursuing the development of analysis methodologies that would aid in the life prediction of composite structures used on military rotorcraft. Such a methodology could eliminate some of the testing requirements, and subsequently reduce not only the cost associated with the testing, but also substantially reduce the development time of the program. Currently, most U.S. airframe companies have ongoing efforts to develop qualification methodologies for composite structures using analytical techniques such as Interlaminar Fracture Mechanics (ILFM). The U.S. Army is currently conducting a technology maturation (6.2) program entitled the Survivable, Affordable, Reparable Airframe Program (SARAP). SARAP is an FY02-05 effort that will demonstrate advanced composite airframe technology. One of the task areas being addressed by SARAP is the development of a Qualification Methodology using Durability and Damage Tolerance. The Qualification, Durability & Damage Tolerance task within SARAP is intended to provide the foundation for a qualification methodology for composite rotorcraft structures. The purpose of this task is to develop durability and damage tolerance methodologies that will reduce qualification costs by applying physics-based models of flaws and damage in advanced, composite rotorcraft structures.