Error-Correction Method Of The Modal Frequency For The Composite Flutter Modal

Wind tunnel flutter test is a crucial part in aircraft design. It is used to investigate the aeroelastic problem and can apply the reference for the structure design of the aircraft. The Aircraft flutter model is the main subject of the wind tunnel flutter test. Its performance is the key factor to determine the success of the flutter test. The composite structure-similarity flutter model (ComSFM) is designed based on the similarity theory and the advanced composite technology. It matches the similarity laws which contain the geometry similarity, the mass similarity,the stiffness similarity and the partial structure similarity. So the ComSFM can satisfy the similar load transmitting with the prototype, can increase the structural efficiency, can reduce the weight of the structure, and can be great significant for the developing of the advanced aircraft.The flutter model is a kind of high performance workpiece which must ensure the precision of the geometry and the performance target. The ComSFM manufacturing is different from the traditional composite structure. Enhancing the structure stiffness simply is unacceptable for ComSFM. At the same time, the complexity of the structure, the dispersed error of composite and the additional stiffness error in assembling are all the important effect factors in ComSFM manufacturing. They lead to that when the geometry of ComSFM has meeted the design, the frequency error always exceeds the allowable range. Here a method was presented to correct the error of the modal frequency. The main works are as follows:First,the error of the modal frequency was converted into the error of the stiffness distribution based on the modal analysis theory and analyzing the manufacturing process of the model. According to the structure dynamics principles and the bending-twisting coupling effect of composite, here an error correction method of frequency was presented for the manufacturing issue of the ComSFM. The core of the method was to add appropriate composite laminates on the skin to change the stiffness distribution of the ComSFM, and then the error of frequency would be corrected by adjusting weight to change the mass distribution.Second, the property of the material and the process of the moulding was explored in order to obtain the distribution of the performance error. The lower deviation control method was adopted to make the performance error of the model compensable. The optimization mathematical model about the error correction scheme was constructed based on the finite element model of the structural dynamics, and the optimal strategy of the NLPQL was used to solve this optimization. By using this strategy,design variables which have small effect on the target function were abandoned,the complexity of the calculation was reduced,the mixed optimization was solved, and the scheme of the adding laminate was obtained.Finally, the experiment to verify the validity of this error correction method was adopted. The wing box was designed through the FEA method, and the contact moulding was used for the manufacturing. The laminate based on the error correction scheme was layup. The result of the modal test showed that errors of the bending frequency and torsional frequency about this the wing box were corrected respectively.So the error correction method is effective.