The Extraction Method Of An Equivalent Beam Model To The Composite Wing And Its Dynamic Property Analysis

With the development of the aerocraft industry of our country, an innovative project on the designning of the aircraft with high-aspect-ratio wings has become one of the most hot topics in the aircraft industry. As the main segement, the optimization of the wing segement has been the main direction of air craft’s optimization. It has advantages including long voyage, fuel saving and stable that most of the transport plane and airbus have been using the wings with high-aspect-ratio. However, it is costly to analyze the dynamic property of the wing with classical finite element method because of the segements are so complicated. So it is necessary for us to find a simple and effective calculational method to work out its natrual frequency and mode shape. Based on above minds, this thesis has focused on the following keypoints:1. Energy equivalent method which is based on the finite element method is given out. The complicated structures is simplified to an Euler-Bernoulli beam by reducing the freedom degeree.The energy stored in the beam is equal to that in the origin structures so that it can be sure they have the equivalent characteristic properties.To work out the section’s parametres,the same disaplacement have been applied.The stiffness properties and interia properties represents the oringin structures thus they terify the accuracy and feasibility of this method.2. Based on the classical laminated theory,the equations of 3D and 2D consitutive relationship of anisotropic material can be deprived.The stiffness propertities of section of a beam consists of slim laminated is given out by solving plane stress problem.As an example,the frequency and mode shape of a cantiliver laminated beam is list and the results is compared to the values of the finite element software.To get the relational graph of the ply angle between modes,the ply angles varied.So it can pave below.3. According to the structural shape of the wing, a cantilever with variable section is adopted to set an equivalent structure for the wing. The caculational method to model the beam with varing section is proposed using the values of specified sections. According to get the torsion coefficient of muti-cell section method, the set of shear flow equations is established and solved. By an example of a muti-cell section beam, its accuracy is confirmed by comparing the results with those from finite element software.4. For the wing with high-aspect-ratio, it is cut into certain wing segements according to the ply and the location of rib. Every wing panel is simplied to a beam element with the energy equivalent method. The stiffness of sections are caculated to compare with the result of the single closed cross-section method. It is also discussed that the addition weight of the finite element method and how to put it into the element mass matrix. At last, put these beam elements into a whole varing section beam and find the frequency and mode shapes. It has been shown that the method proposed here is valid by comparing the results obtained to those from MSC.Patran software.