Research On Nonlinear Static-Dynamic Characteristics And Delamination Growth For Composite Laminated Circular Plates With Delamination

Composite laminates have been widely used in aerospace, automobile and chemical equipment, due to their high strength-to-weight and high stiffness-to-weight, favourable fatigue and vibration resistance, heat stability and designability of material performance. On the other hand, delamination inevitably, delaminated damage arises from manufacturing processes and hit of runway debris, for instance, low energy shock in assembling procedures. The existance of delamination and their further growth will drastically reduce the stiffness and residual strength and life of delaminated plates as well as their their dynamics characteristics. In the dissertation, the composite laminate circular plates with delamination are investigated. Employing the partition region model and appling the plate theory and nonlinear mechanics ,the nonlinear differential governing equations of delaminated circular plate are built. The static buckling , postbuckling, nonlinear free vibration, nonlinear dynamic response ,as well as the delamination growth of composite laminated circular plates with delamination are systematically studied. The effects of delamination size, delamination depth and ply materials on the static and dynamic characteristics of delaminated circular plates are investigated. The main research contents are given as follows.Based on the Von-Kármán plate theory, considering the effect of transverse shear deformation, the buckling and postbuckling model of axisymmetric laminated circular plate with delamination are studied by applying the Reissner variational principle. The orthogonal point collocation method is adopted tosolve the system governing equations. Then ,the influences of delamination depth and radius as well as ply material character on the buckling and postbuckling are discussed in detail. The numerical results are compared with available data.According to the Von-Kármán plate theory and the three dissociate regions model, considering the effect of transverse shear deformation, the post and postbuckling governing equations for the axisymmetric laminated cicular plates with elliptic delamination are derived. By using the modified orthogonal point collocation method, that the crossing points of zero points of Chebyshev polynomial on circular radius and circumferential sectrix curve are taken as collocation points, the governing equations are solved. Then, the effects of elliptical delamination size, delamination depth and material properties on buckling and post-buckling of the laminated circular plates are discussed.Under consideration of geometric nonlinearity, the nonlinear vibration of ortho-symmetric plies axisymmetric circular plate with delamination are investigated. Adopting Bessel function on the space, the dimensionless differential motion equations are got with Galerkin method. The harmonic Balance method is used to solve the equations. Then, amplitude-frequency curves of axisymmetric laminated circular plate in different radius and various depth of delamination sa well as the transverse shear deformation are presentedBased on the Von-Kármán plate theory, employing the three region model, and considering the effect of transverse shear as well as contact between the delaminated surfaces, the nonlinear governing equations of delaminated circular plate with ortho-symmetric plies are obstained. Firstly ,the contact force is derived by regarding the sub-laminate and super-laminate of delamination as two springs connected in serials by Heaviside jumping function. Then, the governing equation of transverse motion is modified by the contact force. The dynamic responses of axisymmetric delaminated circular plate are analyzed by using the orthogonal point collocation method, and the effect of contact on the nonlinear dynamic response of delaminated plates is discussed.By using movable boundary variational principle, and the four dissociated region model, considering the transverse shear deformation and contact effect, the delamination growth of composites laminated circular plate subjected to transverse and radial load is studied repectively. At the same time, according to the Griffith criterion, the formulas of total energy release rate and its individual mode components along the delamination front are obtained. In calculation, the influences of delamination radius and depths, and material properties on energy release rate and its individual components under radial and transverse loads are discussed respectively.