Researches On Macroscopic And Microscopic Mechanisms And Characteristics Of Membrane Wrinkling

Wrinkle is a typical instable mode of the membrane shape. The wrinkling generation and evolution are closely related to the membrane scale. Under different scaling conditions, the wrinkling mechanisms are different which results in different adjusting functions on the membrane properties. For examples, the macro scale wrinkles have great effects on the surface accuracy of space membrane structures, therefore, these wrinkles should be controlled effectively. On the other hand, we may utilize the micro scale wrinkles to tune the properties of microscopic or nanoscale film devices, such as electric properties, optical properties and vibration properties. The research focuses on the mechanisms of macroscopic and microscopic membrane wrinkling and its evolution characteristics. The research has important theoretical meaning for promoting the membrane wrinkling study and engineering meaning for improving the property tuning of membrane structure.The mechanism and characteristics of membrane secondary wrinkling are investigated. The snapping characteristic of wrinkling wave pattern in the process of membrane post-wrinkling stage is analyzed. Based on bifurcation theory, the mechanism of membrane secondary wrinkling is explained as the same critical load corresponding to two wrinkling modes, which is understood as the wrinkling wave pattern changing suddenly corresponding to inverse jumping of the post-wrinkling equilibrium path. A judgment method of the critical state for membrane secondary wrinkling is proposed. Take rectangular membrane wrinkling analysis into account, the critical load of rectangular membrane secondary wrinkling under shear is obtained. Then the crease is introduced into the wrinkling analysis. A wrinkling numerical analysis method of creased membrane is proposed based on quasi-static method. Using this method, the wrinkling behavior of creased membrane is analyzed and the influences of the crease on wrinkling behavior and membrane secondary wrinkling are investigated.The experiment of membrane secondary wrinkling is performed. The experiment method for membrane secondary wrinkling is proposed using digital image correlation technique. The evolution, region and critical load of membrane secondary wrinkling are obtained from experimental results. The validity of the judgment method for membrane secondary wrinkling is verified by using the experiments. It is confirmed that the crease can keep from the wrinkling evolution and secondary wrinkling by experiment. The prediction model of wrinkling amplitude is modified based on the experimental wrinkle strain, which may improve the prediction accuracy on the wrinkling pattern.The evolution characteristics and mechanism of graphene wrinkling are analyzed. The multiple parameters correlation model of graphene elastic parameters is proposed by introducing a correlation factor. The model involves geometry scale, chirality and aspect ratio, simultaneously. The graphene is considered as a continuous membrane. The wrinkling configuration characteristics of graphene are analyzed using macroscopic wrinkling analysis method. Then the similarity relationship between the characteristics of graphene wrinkling and macroscopic membrane is built up. The graphene is then discrete using three-node Timoshenko beam element. The mechanism of graphene wrinkling is explained based on the feature of microscopic structure, which is the torsion deformation energy of carbon-carbon bonds leading to the out-of-plane bending deformation. Finally, the applicability of continuum equivalent method and discretization equivalent method are analyzed for graphene wrinkling.The influence of wrinkling pattern on the vibration properties of graphene is investigated. A prediction model of graphene vibration is set up by inducing the variable mass and variable strain energy caused by features of wrinkling pattern, which are obtained by the continuum equivalent method. The vibration frequency prediction is proposed for wrinkled graphene. Based on above analysis, the influences of different variable configurations caused by defect and functional groups on the vibration properties of graphene are analyzed. The variable frequency rules of graphene with variable configurations are obtained in the end.This research provides a support for the controlling and tuning of membrane wrinkling and is a key reference to design and control the membrane properties based on wrinkle engineering. The research establishes a theoretical principle for further researching on multi-scale correlations of membrane wrinkling.