Study Design and Testing of Structural Configurations for the bird-strike compliance of aeronautical components
Guida, Michele (2008) Study Design and Testing of Structural Configurations for the bird-strike compliance of aeronautical components. [Tesi di dottorato] (Inedito)
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This work is the result of a collaborative research project between the univer- sity (Department of Aerospace Engineering at University of Naples "Federico II") and an industrial partner (Alenia Aeronautica at Pomigliano d'Arco). The aim of this project was to design, with the help of nite element analy- sis and the experimental tests, an aircraft wing leading edge structure with innovative materials, that satises the optimization of requirements such as weight and performance. This study was driven by the industrial demand to improve the design rules necessary to the evaluation of the structural response of a leading edge when subjected to bird-strike. The rst step was the material characterization: an extensive series of materials was tested to determine stiness and strength properties on glass- based ber metal laminate. Static tests were performed to determine the stress-strain curve, dynamic tests to evaluate material strain rate sensitivity at medium rate regime and, impact tests to determine the threshold for impact energy which correspond to visible impact damage. Afterwards several congurations of an one-bay component of a typical wing leading edge were built and subjected to the bird-strike tests carried out at Alenia plant by an air pressure gas gun facility. Various materials, lay-up distribution and boundary conditions were investigated. The numer- ical nite element simulations were performed using the commercial explicit integration code MSc/Dytran. This work describes the basic assumptions of the analyses, i.e. bird properties, composite failure modes, and the way in which the simulations have been carried out in an industrial environment. Numerical simulations were able to predict that the bird did not penetrate the leading edge skin. The nal correlation between numerical and experi- mental showed that good correlation was achieved. Finally the tests were useful to design and test a new conguration of leading edge structure able to satisfy the bird-strike requirement according to the Federal Aviation Regulation (FAR part 25, section 25.631 "Bird-strike Damage"). Compliance with this section we studied the conguration of the C27J aircraft, that presents a cruise velocity of 464km/h (=250kts), so the impact speed with an 8-pound bird is a potentially serious and damaging event that must be accounted for the design of ight critical aircraft com- ponents. The starting thickness of the n C27J airplane's aluminium alloy leading edge was 0.8mm with a weight of 12.1kg. Before this work, to satisfy the airworthiness standards about the bird-strike damages, the thickness of the aluminium alloy leading edge was increased to 3.2mm with a skin weight of 36.8kg, this thickening involved a weight increasing of 305% related to skin thickness of 0.8mm. After this research work, to certicate the empennage structure after im- pact with an 8-pound bird according to requirements, a innovative composite conguration has been studied, which oered an amount weight of 18.2kg producing a weight conservation of 51% related to leading edge in aluminium alloy with a thickness of 3.2mm. Furthermore this research project allows to validate a ribless conguration about the leading edge; this solution aided the manufacturing reducing the rib's installation onto the leading edge struc- ture. The leading edge conguration in the ber metal laminate and ribless has been tested at impact with an 8-pound bird at a speed of 250kts and the test has been considered highly satised and it has met the quality of requirements.
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