Defense Technical Information Center Compilation Part Notice ADP 014084 TITLE : Recognition and Correction of Sonic Fatigue Damage in Fighter Aircraft DISTRIBUTION : Approved for public release , distribution unlimited
High performance aircraft that fly aggressive low altitude or high-angle of attack maneuvers will experience high acoustic loading, especially in the presence of external stores. These high acoustic loadscan lead to rapid sonic fatigue in thin gage metallic structure. As a means of prolonging fatigue life, while at the same time restoring structural load carrying capability in damaged structure, composite bonded repairs which incorporate damping layers have been developed. These damped composite bonded repairs are installed on F-15 flight test aircraft. This paper describes ways to recognize sonic fatigue damage, and the design and flight test results of represeintative damped patches.
Composite material repairs to metallic airframe components
The repair of metal structures by using composite materials is a technology that was pioneered in Australia, and excellent results have been obtained in over 500 repairs of corrosion and fatigue cracking. This paper will present details of the first in-service composite material repair applied to metal structure on USAF C-141B operational aircraft. This engineering study evaluated five locations representing both fatigue and corrosion cracking susceptible areas on the C-141B strategic airlift transport aircraft. Repairs using either boron/epoxy or graphite/epoxy are beneficial for crack retardation, end fastener effect relief, and field stress reduction. The most obvious time saving feature of these repairs is that no fastener removal or installation is involved. Extensive structural analysis utilizing finite element modeling was done to ensure that the repair design not only would have the requisite strength and durability but also would reduce the inspection burden after the aircraft was returned to service. A test program was also undertaken to substantiate the analytical investigation. Typical results from the finite element models as well as the specimen and component tests will be presented. Finally, the step-by-step procedure by which an actual boron/epoxy repair was applied to a fatigue crack on a C-141 center wing will be reported and "lessons learned" will summarize the benefits of applying the technology.
Law in a law-governed union (Recht in einer Rechtsunion) : the Court of Justice of the European Union and the free law doctrine
The Court of Justice of the European Union characterizes the Union as a Rechtsunion: a law-governed union. The conception of “the law” in Article 19 paragraph 1 of the Treaty on European Union transcends the Treaties, according to the Vice-President of the Court of Justice, Koen Lenaerts. This thesis demonstrates with reference to the work of Georg Jellinek that the Union is a non-sovereign state and, with reference to the work of Eugen Ehrlich in particular, that the state-based perception of law is a misperception. Not all production of law is reserved to the state and not all law is state-recognized law. There is extra-state law. It has been alleged that the Court of Justice of the European Union has had “a free law attitude”. The author discusses the free law doctrine developed at the beginning of the twentieth century and has made literal translations of writings in German, French and Italian by the main representatives of the free law movement. The free law doctrine provides a descriptive framework for the case-law of courts. The author describes the creation by the Court of Justice of four constitutional principles of Union law through its case-law. He concludes that every court is, to quote Hermann Kantorowicz, praeter legem law-creatively active and has, in that sense, a free law attitude. The decisions of judges are often volitional decisions. How the law will be applied should be predictable but volitional decisions, because they are unpredictable, are inconsistent with the principle of legal certainty. In the Union and its member states the judiciary and not the statute or “the law” is pre-eminent. The author suggests how the concept of law should be defined in a material Rechtsunion. He argues that societal legal norms could be provided with an appropriate position consistent with the principle of legal certainty by making the validity of a societal legal norm contingent on its material lawfulness.