Effect of bending-twisting coupling on the compression and shear buckling strength of infinitely long plates



题目:Effect of bending-twisting coupling on the compression and shear  buckling strength of infinitely long plates
报告人:Christopher Bronn York
    This article describes  the development of closed form polynomial equations for compression and shear  buckling to assess the effect of Bending-Twisting coupling on infinitely long  laminated plates with simply supported edges.  The equations are used to  generate contour maps, representing non-dimensional buckling factors, which are  superimposed on the lamination parameter design spaces for laminates with  standard ply orientations.  The contour maps are applicable to two recently  developed databases containing symmetric and non-symmetric laminates with either  Bending-Twisting or Extension-Shearing Bending-Twisting coupling. The contour  maps provide new insights into buckling performance improvements that are  non-intuitive and facilitate comparison between hypothetical and practical  designs.  The databases are illustrated through point clouds of lamination  parameter coordinates, which demonstrate the effect of applying common design  heuristics, including ply angle, ply percentage and ply contiguity  constraints.
    Dr. Christopher Bronn  York is Associate Professor at the School of Engineering, University of Glasgow,  UK. His current research activities are focused on the development of a unified  approach to the characterisation of coupled laminated composites involving:  algorithm development for identification and characterisation of coupled  laminate stacking sequence configurations, the vast majority possessing unique  forms of mechanical coupling behaviour not previously identified; critical  assessments of the benefits, or otherwise, to a wide range of functional and/or  structural material applications and; development of laminate benchmark  configurations, with properties exhibiting behaviour similar to conventional  (metallic) materials, and against which all unique forms of laminate behaviour,  arising from isolated and combined mechanical coupling effects, are being  characterised.
    Recent discoveries  include twenty-four unique classes of mechanically coupled laminate. One new  laminate class possesses in-plane coupling behaviour only, i.e.  extension-shearing coupling. Such laminates can be configured to produce  bending-twisting coupling in wing-box type structures, which can be exploited to  great effect in the design for passive load alleviation in wind-turbine blades,  or for aero-elastic compliance in helicopter rotor-blades. Similar behaviour can  also be achieved by using less sophisticated designs, such as applying off-axis  material alignment to otherwise balanced and symmetric laminates, but additional  forms of coupling behaviour arise in these cases, leading to detrimental effects  on both stiffness and strength. Other exotic forms of mechanical coupling have  also been newly discovered, and contrary to long held misconceptions, a  surprisingly broad range of these designs can be manufactured without the  undesirable warping distortions that generally result from the high temperature  curing process. Such laminate designs may be described as Hygro-Thermally  Curvature-Stable (HTCS) or warp-free and are likely to become an import enabling  technology in future ‘smart’ structures.