The Design And Analysis Of Mechanical Metamaterials With Tailorable Thermal Expansion And Tunable Poisson’s Ratio

Mechanical metamaterials attract enormous attention due to its spectacular mechanical properties in the field of metamaterials.Among the various excellent mechanical performance,the properties with tailorable coefficient of thermal expansion(CTE)and tunable Poisson’s ratio(PR)are most popular in the research areas and engineering applications.However,current literatures reported that,the majority of metamaterials can only achieve tailorable thermal expansion or tunable Poisson’s ratio,which makes them not available in the application of thermal-mechanical multifield coupling working conditions.In this thesis,three-dimensional lightweight metamaterials with large positive,zero and negative thermal expansion are designed.Moreover,a 2D metamaterial incorporating coupled negative thermal expansion and negative Poisson’s ratio is developed.Furthermore,based on the 2D metamaterial,the corresponding 3D metamaterials are designed.The main researches are listed as below:In the design of 3D metamaterials with large tailorable thermal expansion,theoretical analysis and numerical verification of bi-material pyramid and tetrahedron unit cells are made.Furthermore,two three dimensional structures PA and PB,with isotropic tailorable CTEs are originally devised.Moreover,a reconstruction method,which can reconstruct an arbitrary 3D truss structures with specific target CTEs,is innovatively developed.In the design of the 2D metamaterial integrated coupled tailorable thermal expansion and tunable Poisson’s ratio,the design method s and geometrical constraints are given.Besides,the analytical expressions and numerical simulations of the CTE and PR are conducted to exhibit the good tailorable capacity of the newly designed metamaterial.The 3D metamaterials with coupled tailorable thermal expansion and tunable Poisson’s ratio are also designed based on the 2D metamaterial above.Similarity,the CTE and PR are analyzed from the perspective of theory and simulation.The results show that the developed 3D metamaterials can achieve coupled tailorable thermal expansion and tunable Poisson’s ratio under the reasonable selection of mater ial and geometrical parameters.