A new damage feature index is presented for the structural health monitoring based on Hilbert-Huang transform (HHT). The energy marginal spectrum of the dynamic signal is used to construct damage characteristic parameter, which can reflect the signal energy variation and benefit the structural damage detection. A sinusoidal wave with frequency change and a composite plate vibration experiment with pre-defined damage are designed to verify the effectiveness of characteristic parameter in damage detection. Results obtained from simulation and test show that the extracted non-model-based damage feature index is available and sensitive in damage detection of time-varying system.

A flexible high aspect ratio wing (HARW) generate large structural deformations. The nonlinear static aeroelastic and flutter characteristics analysis for the wing were performed using a nonlinear approach based on the computational fluid dynamic and computational structure dynamics (CFD/CSD) coupled method. The structural analysis was performed using a high efficiency nonlinear 4-node thin shell element based on the co-rotational (CR) method and the developed 4-node linear element to analyse large structural deformations. The load was calculated by the CFD solver. The result showed that the change of aerodynamic load led to a decrease of pressure difference between the upper and lower airfoils, especially the locations between the front and rear beams. At the attack angle of 6°and flight speed of 0.75 Ma, the maximum deflection and torsion angle of linear wing structure were approximately 13.27% and 32.38% greater than that of nonlinear wing structure, respectively. Because of the influence of nonlinear characteristic, the vertical and spanwise displacements and torsion angle of wing cross-sections were less than the linear result under the same flight attitude. The experimental results of the AGARD 445.6 wing verified the accuracy of the established flutter analysis method. The influence of the geometrical nonlinear characteristics of the structure caused by large deformation must be considered during the flutter characteristic analysis of the high aspect ratio composite wing, and the limit cycle oscillation (LCO) phenomenon cannot be obtained by the linear structure in the flutter analysis.

A simple method was presented by means of FE software to fix on the location of stiffness-center axis of a high-ratio-aspect composite wing model. The most difference was 7.5%, comparing the results of FE method with that of theoretical method. It was applied to an example of engineering. The optimal design was carried out with the location of stiffness-center axis of a composite wing as objective function and static strength and stability as constraints. The design variables were the lay-up thickness of panel and spar web, and the cross-section area of stringer and spar edge. Through the iterative calculation by multi-island genetic algorithm and sequential quadratic programming, the optimized location of stiffness-center axis of composite wing model was obtained finally. Compared with that optimized before, the location of stiffness-center axis is closer to leading edge of the wing.