Using strain energy-based prediction of effective elastic properties in topology optimization of material microstructures

An alternative strain energy method is proposed for the prediction of effective elastic properties of orthotropic materials in this paper. The method is implemented in the topology optimization procedure to design cellular solids. A comparative study is made between the strain energy method and the well-known homogenization method. Numerical results show that both methods agree well in the numerical prediction and sensitivity analysis of effective elastic tensor when homogeneous boundary conditions are properly specified. Two dimensional and three dimensional microstructures are optimized for maximum stiffness designs by combining the proposed method with the dual optimization algorithm of convex programming. Satisfactory results are obtained for a variety of design cases. The project supported by the National Natural Science Foundation of China (10372083, 90405016), 973 Program (2006CB601205) and the Aeronautical Science Foundation (04B53080). The English text was polished by Keren Wang.  

Cell size effects for vibration analysis and design of sandwich beams

In this work, sandwich beams are studied to reveal the underlying size effects of the periodic core cells for the first time within the framework of free vibration analysis of such an advanced lightweight structure. The energy equivalence method is formulated as a theoretical approach that takes into account the cell size effect. It is compared with the asymptotic homogenization method and direct finite element method systematically to show their consistence and applicability. The accuracy of free vibration responses predicted by the detailed finite element model is used as the standard of comparison. It is shown that the cell size is an important parameter characterizing the cellular core rigidities that influence vibration responses. The homogenization model agrees exactly with the asymptotic solution of the analytical expression of the beam model only whenever the cell size tends to be infinitely small.