Design And Preparation Of Multistable Structures Based On Composite Laminates With Variable Section

Multistable structures which have numbers of stable configurations can snap from one stable configuration to another with the help of driving force. In the process of snap-through, multistable structures have low stiffness to enable large deformations, while still being sufficiently stiff to withstand external load. Fulfilling these conflicting requirements of low mass, deformable and high stiffness makes multistable structures have a nice application prospect in the morphing structures.From the point of the stiffness tailoring, this paper designs the laminate by using the variable cross-section method and builds the multistable structure, via prestress, based on the variable cross-section laminate. This paper carries on the experiments and analysis on stable configurations, critical snap-through load,actuation method of the multistable structure.Based on the piecewise variation of lay-up, this paper first designs the lay-up of laminate and a multistable structure is built with the out-of-plane displacement constraints being applied on the laminate. The critical load of the multistable structure is tested by using the small cupping machine. The snap-through process of the multistable structure under center load is simulated and analysised with the finite element method. Based on the results of experiment and finite element analysis, four hypotheses are proposed and a theoretical model is built, on that hypotheses, to predict the stable configurations and critical load of multistable structures. The results of theoretical model are compared with experiments and the finite element analysis. After the study on the mechanics properties of multistable structures, two kinds of snap-though actuation methods with magnetic force actuator and push-pull electromagnet actuator are proposed and the effectiveness of these actuation methods is then verified in experiments. An idea of application is proposed based on such multistable structures for controlling fluid flow.By improving the design of lay-up, a tri-stable structure is obtained, which has three different S-shaped stable configurations. Parameter analysis is done to inspect some parameters like lay-up with emphasis on the critical load. A theoretical model is built to predict the critical load after correcting the laminate’s section flexural rigidity. The results of theoretical model are compared with the finite element analysis. In the end, a actuation method with inflatable bladder actuator is proposed,the effectiveness of such actuation methods is then verified in experiments and finite element analysis.