Damping Mechanism And Vibration Control Of Periodic Cellular Composite Structure

As an epoch-making generation of mechanical metamaterials,auxetic materials have been extensively studied all over the world.At present,an abundant mount of researches have concentrate on the design,manufacturing techniques,impact energy absorption,and basic mechanical performance.However,the study on the vibration and damping performance of auxetic materials has been still in the preliminary stage and rarely reported.In this dissertation,2D and 3D double-arrow-head auxetic sandwich shell structure and cylindrical structures,2D double-arrow-head auxetic damping shock absorbers,2D re-entrant anxetic cellular structures are designed.The vibration damping characteristics and energy dissipation mechanism are investigated by numerical simulations,based on the structural damping integration technique.The main contents are as follow:Firstly,the composite material curved shells,axial corrugated curved shells and axial corrugated curved cylinders are fabricated by a hot press moulding postforming method.Three types of composite structures have been investigated using the modal test and numerical method.The modal shapes and the natural frequency from the numerical method show good agreement with the results from the experimental test.The finite element numerical simulation method has been provided for the third and fourth chapters to study the vibration damping characteristics of the double-arrow-head auxetic sandwich shell structures and the auxetic damping shock ring column absorbers.Then,2D and 3D double-arrow-head auxetic sandwich shell structure and cylindrical structures are designed.The vibration damping characteristics are studied by the finite element software ABAQUS.The damping energy dissipation mechanism is revealed by analyzing the variation of damping contribution factors.The result show that the double-arrow-head auxetic sandwich shell structure and cylindrical structures with the different damping mechanism are a reasonable and efficient kind of damping damping shell structures.The damping loss factor of the two-dimensional double-headed longitudinal sandwich cylindrical structures are above 2.0,while the damping loss factor of the two-dimensional double-headed circular sandwich cylindrical structures is above 2.5,each step is slightly larger than the former,and the overall trend is increasing with increasing frequency.It is a reasonable and efficient damping structure.Finally,2D double-arrow-head auxetic damping shock absorbers,2D re-entrant anxetic cellular damping shock absorbers,2D double-arrow-head auxetic damping shock ring column absorbers and 2D re-entrant anxetic cellular damping shock absorbers are designed.The vibration damping characteristics are studied by the finite element software ABAQUS.The damping energy dissipation mechanism is revealed by analyzing the variation of damping contribution factors.The effect of different characteristic angle configurations on the basic vibration characteristics and damping mechanism of each structure was investigated detailedly.It is concluded that four kinds of structures have better vibration damping and energy dissipation performances.In contrast,the two-dimensional concave honeycomb column with the 75? concave angle has a larger natural frequency and better damping performance.The sixth-order loss factor reaches a high value of 2.91.Because the 2D re-entrant anxetic cellular structures is a shear-dominant deformation damping structure,it would be a kind of the high-damping,vibration-reducing,high-efficiency mechanical metamaterial structure.