40207_48 - AIRCRAFT APPLICATIONS Richard N Hadcock 48 48.1...

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AIRCRAFT APPLICATIONS 48 Richard N. Hadcock 48.1 INTRODUCTION metal aircraft structures. However, there are Advanced composites, composed of high- strength, high modulus, low density continuous fibers embedded in polymer matrices, first became available some 30 years ago. Since then, composite aircraft structures have transitioned from laboratory curiosities into low-risk, light-weight alternatives to metal structures. Thousands of safety-of-flight composite components are flying in regular service on military and civil aircraft. Major advantages of high-performance composite structures include weight savings, material tailorability, improved fatigue and corrosion resistance. Disadvantages are pri- marily cost related. Almost all the composite structures currently in production and service have thermoset matrices. A few aircraft parts are currently being made from thermoplastic matrix composites. Metal matrix composites are still in the development stage. 'Conventional' aircraft structural materials now include polymer matrix composites in addition to aluminum, titanium and steel. The chronology of utilization of different rein- forced plastics is shown in Fig. 48.1. 48.2 DESIGN AND CERTIFICATION REQUIREMENTS The general structural design and certification requirements apply to both composite and some basic differences between the generic civil and military requirements and further variations associated with the intrinsic differ- ences between the structural behavior of metals and composites. The US Federal Aviation Regulations (FAR) for civil aircraft and the US Air Force (USAF) and US Navy (USN) military aircraft require- ments have differences. The European Joint Airworthiness Requirements (JAR) are similar to the FAR and have a similar numbering sys- tem, but, again, there are some differences. FAR sections related to design and certifica- tion of aircraft, aero engines and propellers contain more than 600 pages'. The equivalent USAF documents contain almost 400 pages and distribution is restricted. Although the requirements are applicable to both metal and composite structures, certifi- cation of composite structures is very much more extensive and requires many more tests. The contractor must fabricate and test thou- sands of specimens and hundreds subcomponents to qualify a single new car- bon/epoxy system and associated structural details. As an example, the material qualification program for the all-composite Beech Starship included collection and analysis of thousands of data points from element, panel and sub- component tests. Finally, fatigue and residual strength tests were made of a complete air- frame2f3. A similar test program was used by -- CASA to certify the Airbus A320 Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7 carbon/epoxy stabilizefl.
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Advanced composite materials 1023 Colton/ x- -.
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40207_48 - AIRCRAFT APPLICATIONS Richard N Hadcock 48 48.1...

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