| Both in the field of aerodynamic research and the process of aircraft design, flutter has always been an important research topic. Bifurcation, cycle times, chaos and many other phenomena often occur with flutter. So flutter is one of the most mysterious phenomena difficult to predict. If the speed of aircraft meets or exceeds the flutter critical velocity, flutter will occur. Flutter will lead to serious consequences, even slight flutter also could trigger the fatigue damage of aircraft structure. As a result to improve the flutter critical velocity of aircraft has been the research subject and direction of scientists and engineers. Both the active way and passive way are the control methods of flutter. For its convenient, stable and reliable effects, generally aircraft designers choose the second way to control flutter primarily.This paper carried out simulation analysis on increasing flutter velocity of wings which are made of new brand carbon-fiber composite materials based on Theodorsen aerodynamic force function, strip theory and the flutter passive control method, during which, the simulation is accomplished by finite analysis software Hypermesh and Nastran. Firstly this article gives a presentation of background of flutter includes the emergence of flutter and its status in mechanical system. And then two-dimensional wing flutter calculation formula was deduced based on Theodorsen aerodynamic force function. Then introduced how to use the two main methods, K method and PK method, to compute flutter critical velocity. By a simple contrast, choose PK method as the analysis way of this paper. Then divide the wing structure into elements by Hypermesh, so a finite element model of a certain type aircraft wing structure is obtained. Then the analysis of wing structure mode and flow field is carried out, preparing for flutter analysis. Then calculate the flutter critical velocity of wings on which flutter mainly occurs by PK method. Finally choose new brand carbon-fiber composite materials, M55 J, laminate as wing skin to compute flutter critical velocity. Considering the anisotropy characteristic of carbon fiber composite material, laminates with different ways of layer have different mechanical properties. Therefore this paper calculate the flutter critical velocity of wings made of laminates with different carbon fiber layer. Then make conclusion by comparing the results.This paper has gotten following conclusion: 1. With the development of technology, the costs of new type composite materials continues to reduce. Carbon fiber composite materials has a large-scale application in the field of aviation. But by the anisotropic characteristics, different layer method leads to different mechanical property of the laminates made of carbon fiber. By the improper layer method, not only can’t take advantage of the asset of composite materials but also make the wings flutter critical velocity lower than the wings skin made of traditional metal materials.2. To two-dimensional wing, flutter always occurs in bending-torsional coupling modal. At this time, surface fibers of the laminates bear shear effect mainly. And the fibers of 45 degree direction could resist shear stress effectively. So make the surface fiber of wings skin 45 degree direction what could improve the flutter velocity of wings significantly.3. Keeping the thickness of laminates, increase fiber laying layers with finer carbon fiber what could make fibers of each different angle distribute more evenly. to some extent, This way could improve the wings flutter velocity. But it could also increase the cost of materials greatly, and the effect is very limited. So before using this method, consider carefully.4. Compared with the traditional metal materials, choosing the new carbon fiber composite materials laminates layered by reasonable way to manufacture wings skin could make the flutter critical speed of wings could improve more than 20%. So improving wings flutter critical velocity by new type composite materials is a promising method. |
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