In order to asses the impact behaviour of a sandwich structure actually used on a real helicopter frame, an experimental-numerical activity has been executed. The panel specimen tested is representative of the full technological process, and it is made with a sandwich construction, with two aluminium skins (Al 2024 T3) and a Nomex honeycomb core. The experimental set up for low velocity impact has been built in order to allow the free fall of a guided impacting mass with energy up to 100 J. According to the ductile behaviour of the skin material, the tests have been carried out increasing the energy involved in order to acquire the threshold value in which a failure happens on the skin. This is a critical situation because after the skin fail, a crack could propagate under the flight spectrum loads. A FE model has been developed to simulate the tests with particular attention to the material characterization. In order to reproduce exactly the behaviour of the Nomex honeycomb (key characteristic in the impact prediction) a flatwise test has been executed. For how concern the aluminium, a characterization of hardening and fracture locus of the material has been inserted in numerical model. The complete material characterization allows to simulate with encouraging results the fracture of the skin at near the threshold energy.
LOW VELOCITY IMPACT BEHAVIOUR OF AL-NOMEX SANDWICH PANELS
MANES, ANDREA;GIGLIO, MARCO
2010-01-01
Abstract
In order to asses the impact behaviour of a sandwich structure actually used on a real helicopter frame, an experimental-numerical activity has been executed. The panel specimen tested is representative of the full technological process, and it is made with a sandwich construction, with two aluminium skins (Al 2024 T3) and a Nomex honeycomb core. The experimental set up for low velocity impact has been built in order to allow the free fall of a guided impacting mass with energy up to 100 J. According to the ductile behaviour of the skin material, the tests have been carried out increasing the energy involved in order to acquire the threshold value in which a failure happens on the skin. This is a critical situation because after the skin fail, a crack could propagate under the flight spectrum loads. A FE model has been developed to simulate the tests with particular attention to the material characterization. In order to reproduce exactly the behaviour of the Nomex honeycomb (key characteristic in the impact prediction) a flatwise test has been executed. For how concern the aluminium, a characterization of hardening and fracture locus of the material has been inserted in numerical model. The complete material characterization allows to simulate with encouraging results the fracture of the skin at near the threshold energy.File | Dimensione | Formato | |
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ECCM14_Low velocity impact behaviour of Al-Nomex sandwich panels DEFINITIVE VERSION.pdf
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