Mechanical Properties And Optimization Of Ultra-light Weight Sandwich Structures

Ultra-light weight sandwich structures have excellent mechanical properties and multifunctional performance, so materials scientist and engineer pay great attention to these structures. Firstly, this paper introduces briefly the state of arts of mechanical properties and optimization of these structures, then analyzes and optimizes several typical ultra-lightweight sandwich structures based on finite element software ANSYS. Main contents and conclusions are as follows:The regular hexagonal honeycomb web is replaced by linear elastic Bernoulli-Euler beam, and the equivalent elastic parameters of regular hexagonal honeycomb core are predicted. The 3D finite element model of regular hexagonal honeycomb core has been established, the equivalent elastic parameters of regular hexagonal honeycomb core plane have been successfully simulated. Great deviation exists between the results using Bernoulli-Euler beam method and the experiment results with aluminum honeycomb core from Ref ~[44], while the results from FEM and the same reference results have good agreement.The optimization of buckling-prone cylindrical hollow tubes and tubes with foam materials cores is studied. The buckling modes and the load-carrying efficiency (the ratio of the critical load to the weight) of cylindrical hollow shells subject to axial compression are studied. The parameters, such as the shell thickness and the relative density of foam core, influence the structural buckling modes and the load-carrying efficiency of the cylindrical shells with foam cores. A parametrical finite element modeling method and an optimization program written in APDL language of ANSYS are presented.With the same metal material, the same geometrical dimension and the same relative density of core, the parametrical finite element modeling of foam core sandwich beam, honeycomb core sandwich beam and periodical truss core sandwich beam are developed, respectively. The strength rule and stiffness restrict are considered, and the non-dimensional load index and weight index are proposed, these structure in 3-Point bending are optimized, the load index-weight index curve is obtained. Results indicate that periodical truss core sandwich beam is highly efficient from viewpoint of weight.To overcome the drawback of single certain loading case in multi-objective optimization, multi-objective and multi-loading optimization of ultra-light weight sandwich structures are studied. The statistical concepts are introduced, and a suitable quantitative evaluation criterion for multi-objective and multi-loading optimization is proposed. Finally this approach is used in optimization of periodical truss core sandwich panel.