An engineered Negative Poisson's Ratio (NPR) material is investigated in this paper for its design variations based on two design variables. The investigated material properties include effective Young's modulus, Poisson's ratio, material density, and load-bearing efficiency in terms of rigidity/weight ratio of the material. Nonlinear behaviors of the design variations are also investigated for large deformation applications. It is seen that by varying the two design variables, the NPR can reach as low as minus sixty in a special design. Any NPR number between a positive number and minus sixty can be obtained within the design domain through the design process. The nonlinear analysis results show that the effective material properties vary depending on the load amplitude, and the NPR material becomes stiffer and stiffer when the compression load is increased. The finite element method is utilized with a multi-step linearization method to predict the nonlinear behaviors of NPR materials. This will allow the effective material properties to be calculated for any given load amplitude. The new capability can be then used to design desired NPR material in a function-oriented material design (FOMD) environment for advanced application development. Both linear and nonlinear analysis results are presented and compared in this paper in order to demonstrate the necessity of accounting for geometric nonlinearity in the NPR material design process. An NPR material simulation and design system, called FOMD-NPR, has also been developed at MKP Structural Design Associates, Inc. for designing innovative NPR materials for various applications.
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