Study Design and Testing of Structural Configurations for the bird-strike compliance of aeronautical components
Creators: name: Guida, Michele
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2008

description: 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.