Optimization of Mechanical Properties of Multiphase Materials with Auxetic Phase

Auxetic materials and structures exhibit negative values of Poisson's ratio, which is the source of their unusual deformation pattern. Auxetic materials can be utilized in the development of multiphase materials with increased Young's modulus by properly distributing the different phases in the volume of composite material and utilizing the auxetic effect. This work presents the results of an optimization of multiphase materials with an auxetic phase, with the aim of obtaining increased stiffness and near-zero lateral strain. Geometries of auxetic unit cells and conventional unit cells were subjected to optimization to obtain the desired values of effective material properties via multiscale modelling. Values of material properties of all considered phases were obtained via multiscale modelling of representative volume elements of their respective auxetic and conventional unit cells. Four types of unit cells and three types of inclusion patterns in the hybrid material sample were considered. The simulation results demonstrate that the application of an auxetic phase region in the multiphase material allows it to obtain effective Young's modulus greater than that of component phases, as well as near-zero lateral strain during uniaxial tension of the sample. Increase of effective Young's modulus and significant reduction of effective Poisson's ratio of the sample were obtained in all considered optimization cases.