Response of thin-skinned sandwich panels to contact loading with flat-ended cylindrical punches: Experiments,numerical simulations and neutron diffraction measurements |
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| Affiliation: | 1. Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, Sydney, NSW 2234, Australia;2. The Bragg Institute, Australian Nuclear Science and Technology Organisation, (ANSTO) Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia;3. School of Mechanical and Manufacturing Engineering, University of New South, Wales, Sydney, NSW 2052, Australia;1. Department of Civil Engineering & Geomatics, Cyprus University of Technology 3036, Limassol, Cyprus;2. Centre of Offshore Renewable Energy Engineering, Cranfield University, MK43 0AL, UK;3. Department of Civil & Environmental Engineering, Imperial College of Science Technology and Medicine, South Kensington Campus, SW7 2AZ, UK;1. New York University, United States;2. St. Petersburg Department of Steklov Institute of Mathematics, Russian Federation;3. St. Petersburg Academic University and St. Petersburg Department of Steklov Institute of Mathematics, Russian Federation;1. Department of Mathematical Modelling, Tver State University, 35 Sadoviy per., 170002 Tver, Russia;2. Nonlinear Physics Centre, Research School of Physical Sciences and Engineering, The Australian National University, Canberra ACT 0200, Australia;3. Institute for Metals Superplasticity Problems, Khalturin Str. 39, Ufa 450001, Russia;4. St. Petersburg State Polytechnical University, Polytechnicheskaya 29, 195251 St.Petersburg, Russia |
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| Abstract: | The response of aluminium foam-cored sandwich panels to localised contact loading was investigated experimentally and numerically using flat-ended cylindrical punch of four varying sizes. ALPORAS and ALULIGHT closed-cell foams of 15 mm thickness with 0.3 mm thick aluminium face sheets (of 236 MPa yield strength) were used to manufacture the sandwich panels. Face sheet fracturing at the perimeter of the indenter, in addition to foam cells collapse beneath the indenter and tearing of the cell walls at the perimeter of the indenter were the major failure mechanisms of the sandwich panels, irrespective of the strength and density of the underlying foam core. The authors employed a 3D model in ABAQUS/Explicit to evaluate the indentation event, the skin failure of the face sheets and carry out a sensitivity study of the panel's response. Using the foam model of Deshpande and Fleck combined with the forming limit diagram (FLD) of the aluminium face sheet, good quantitative and qualitative correlations between experiments and simulations were achieved. The higher plastic compliance of the ALPORAS led to increased bending of the sheet metal and delayed the onset of sheet necking and failure. ALULIGHT-cored panels exhibited higher load bearing and energy absorption capacity, compared with ALPORAS cores, due to their higher foam and cell densities and higher yield strength of the cell walls. Additionally, they exhibited greater propensity for strain hardening as evidenced by mechanical testing and the neutron diffraction measurements, which demonstrated the development of macroscopically measurable stresses at higher strains. At these conditions the ALULIGHT response upon compaction becomes akin to the response of bulk material with measurable elastic modulus and evident Poisson effect. |
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| Keywords: | A Foams B Mechanical properties C Finite element analysis (FEA) D Mechanical testing Neutron diffraction |
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