The Snap-through Analysis Of Bi-stable Laminate And Performance Evaluation Of New Flexible Honeycomb Structure

Morphing aircraft is the developing direction of future aircraft, researching high bearing capacity and large deformation structure and materials is one of the key technologies. The morphing structure and materials require high bearing capacity and large deformation ability, and small reaction force in the process of morphing. Multi-stable structure have a variety of stable configurations and can meet many conditions of pneumatic design, at the same time it don’t need additional reaction force, so it is the potential candidate to the morphing structure. Honeycomb material uses the wall bending deformation can achieve10times greater than the base elastic material deformation, and composite flexible honeycomb structure is one of ideal candidates to the variant skin structure. In view of the above two candidates, this paper has carried out two fields:Firstly, for bi-stable laminate, we proposed a more accurate analytical method of quasi-static and dynamic snap-through; Secondly, we proposed a new flexible cellular structure that have a lower driving force and greater deformability, and evaluated its performance. The details are as follows:(1) The quasi-static theoretical analysis model of bi-stable laminate. Accurately predicting the stable configuration and snap-through load is the key to the multi-stable structure design. There is a big error in predicting the snap-through load for analysis model based on the literature created quadratic polynomial function of displacement, so we proposed high order polynomial function to improve the theoretical analysis model, and theoretical model results and finite element analysis results were comparative analysis. The results show: The new theoretical model can significantly improve the prediction accuracy of stable configuration and reduce the errors of snap-through load, proved the accuracy of the theoretical model presented in this paper.(2) The dynamic theoretical analysis model of bi-stable laminate. In engineering most of snap-through between stable configurations is instantaneously, so researching the dynamic snap-through process of stable configurations is very important. In this paper we established a dynamic snap-through analysis model based on fourth-order polynomial function, carried out no damping and damping dynamic analysis of asymmetric ply laminate and theoretical model results and finite element analysis results were comparative analysis. The results show:In the no damping conditions, this paper presented analysis model is more closer to the finite element analysis results compared with the literature results (quadratic polynomial) in predicting the snap-through load and vibration frequency, and the deviation of the finite element analysis results with theoretical models are in the smaller range. In the damping conditions, in each of the snap-through load, the snap-through time of theoretical model results and finite element analysis results do not differ more than0.5seconds, the theoretical model have high precision. So by studying the theoretical model analysis results in static and dynamic snap-through can be found, the new theoretical model solved the problem of quadratic large error, and have good accuracy.(3) Performance analysis of octagon zero Poisson’s ratio flexible honeycomb structure. The flexible composite material of the honeycomb structure is a candidate material for the morphing structure. By analyzing the deformation mechanism of zero Poisson’s ratio hexagonal honeycomb structure, proposed a new zero Poisson’s ratio octagon honeycomb structure, given the analytic expression of equivalent modulus and maximum deformation rate, by comparing the results with finite element analysis, proved the accuracy of the analytical solutions. On this basis, by contrast with the hexagonal honeycomb shows:octagon honeycomb structure has a lower stiffness in deformation direction, and greater deformation ability, In addition, using parametric analysis, researched wall thickness and length parameters to the effect of performance, provide a reference for practical design.