The report reviews the application of applied fracture mechanics in the design, analysis and qualification of aircraft structural systems. Recent service experiences are cited. Current trends in high strength materials application are reviewed with particular emphasis on the manner in which fracture toughness and structural efficiency may affect the material selection process. General fracture control procedures are reviewed in depth with specific reference to the impact of inspectability, structural arrangement and material on proposed analysis requirements for safe crack growth. The relative impact on allowable design stress is indicated by example. Design criteria, material and analysis requirements for implementation of fracture control procedures are reviewed together with limitation in current available data techniques. A summary of items which require further study and attention is presented.

This book consists of a collection of lectures prepared for a short course on "Fracture Mechanics Methodology" sponsored by the Advisory Group for Aerospace Research and Development (AGARD), part of the North Atlantic Treaty Organization (NATO). The course was organized jointly by Professor George C. Sih of the Institute of Fracture and Solid Mechanics at Lehigh University in the United States and Professor Luciano Faria from Centro de Mecanica e de Materiais das Universidade de Lisboa in Portugal. It was held in Lisbon from June 1 to 4, 1981. Dr. Robert Badaliance from the McDonnell Aircraft Company in St. Louis and Dr. Oscar Orringer from the Depart ment of Transportation in Cambridge are the other US lecturers while Professor Carlos Moura Branco from Portugal also lectured. The audience consisted of engineers from the Portuguese industry with a large portion from the aeronautical sector and others who are particularly interested to apply the fracture mechanics discipline for analyzing the integrity of structural components and fracture control methods. Particular. emphases were given to the fundamentals of fracture mechanics as applied to aircraft structures.

The paper discusses the implementation of the Force Management (FM) phase of the Aircraft Structural Integrity Program (ASIP) for a USAF utility transport/trainer aircraft. The analyses, performed in support of the Force Management tasks, use the principles of linear elastic fracture mechanics with emphasis on subcritical flaw growth. The durability and damage tolerance lives, generated with a crack growth computer program, are the basis for structural maintenance recommendations and inspection intervals presented to the USAF in the Force Structural Maintenance Plan (FSMP).

Design criteria and analysis procedures are presented such that a design system can be implemented to minimize the occurrence of major structural failures due to the presence of undetected damage. The design criteria define a flaw growth durability requirement and crack growth structural integrity requirements for three classes of inspectability of the structure; noninspectable, NDI in-service inspectable, and walk-around inspectable. Currently available crack growth and residual strength methods of analysis are presented which can be used to predict the remaining life and strength of damaged structure. To illustrate the use of the criteria and methods of analysis, a design study was conducted of the lower wing surface of a fighter/ attack aircraft. The results of this study indicate that the structure could meet the design criteria with little or no weight penalty using 7075-T76 aluminum and annealed Ti-6Al-4V, and provided adequate inspection techniques and inspection frequencies are applied throughout the life of the aircraft.

Aircraft Sustainment and Repair is a one-stop-shop for practitioners and researchers in the field of aircraft sustainment, adhesively bonded aircraft joints, bonded composites repairs, and the application of cold spray to military and civil aircraft. Outlining the state-of-the-art in aircraft sustainment, this book covers the use of quantitative fractography to determine the in-service crack length versus flight hours curve, the effect of intergranular cracking on structural integrity and the structural significance of corrosion. The book additionally illustrates the potential of composite repairs and SPD applications to metallic airframes. Covers corrosion damage assessment and management in aircraft structures Includes a key chapter on U.S. developments in the emerging field of supersonic particle deposition (SPD) Shows how to design and assess the potential benefits of both bonded composite repairs and SPD repairs to metallic aircraft structures to meet the damage tolerance requirements inherent in FAA ac 20-107b and the U.S. Joint Services