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Title: Structural integrity of open-cell aluminium foam sandwich panels for lightweight wing structures
Author: Betts, Charles
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The overarching aim of this work was to concentrate on the mechanical modelling and experimental characterisation of novel open-cell aluminium foam core sandwich panels for prospective use as an airplane wing skin material. A repeating unit cell 2D FE model was created to assess the mechanical behaviour of infinitely long, regularly tessellated honeycomb core sandwich panels. An analytical model using Timoshenko beam theory was developed to predict the Young’s modulus of a hexagonal honeycomb core; there is good agreement between the two models. A microtensile test procedure was developed to determine the mechanical properties of individual foam struts. A FE model of the as-tested struts was created, using XMT scans of the undeformed struts to define the geometry, to establish a method that compensates for grip slippage inherent in the testing of the struts. Strut deformation was described by a calibrated continuum viscoplastic damage model. The damage model was implemented into 3D FE models of an open-cell aluminium alloy foam core sandwich panel subjected to uniform compression to study the effect of varying the strut aspect ratio on the mechanical properties of the core. FE models of the panel subjected to three and four point bending were created to provide a virtual standardised test to assess the core elastic properties. The extent of structural damage in the panels was simulated for indentation loading indicative of a tool strike; an optimal strut aspect ratio was identified providing the best energy absorption per unit mass whilst ensuring core damage is detectable. The effect of morphological imperfections on the mechanical properties and extent of detectable damage of the core was studied. The shear modulus of the core was greatly reduced under the presence of both fractured cell walls and missing cells. The extent of visible damage was largely unaffected by either type of defect.
Supervisor: Balint, Daniel ; Lin, Jianguo Sponsor: Engineering and Physical Sciences Research Council ; Airbus Industrie
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available