Dynamic Stability Of Composite Laminates And Piezoelectric Smart Laminates Structure With/without Delamination

Study on nonlinear dynamic stability for composite laminates and piezoelectric smart composite laminates with/without delamination subjected by axial periodic dynamic load have been carried out,respectively,in the dissertation.The main research contents and results are as follow,(1) The nonlinear dynamic stability of composite laminatesOn basis of Reddy's simple higher order shear deformation theory,a dynamic instability equation,called Mathieu equation,was deduced.The analytical expressions of solution corresponding to the equations were given.Dynamic instability of the parameter vibration was investigated.From some typical examples,it is clear that the effects of nonlinear factors upon the instability regions and amplitude of parameter vibration are significant,and the influences of ratio between tension and transverse bending stiffness,and linear and nonlinear damp on the maximum deepness of "traction" were also discussed.(2) The nonlinear dynamic stability of composite laminates with delaminationA delaminnation model of composite laminates was established,a dynamic instability equation,called Mathieu equation,considering the nonlinear elastic and damping effects,was deduced.The dynamic instability of the parameter vibration was investigated.From some typical examples,it is clear that the effects of delamination lengths and locations on the natural frequency,buckling load and instability regions,and the effect of excitation frequency of dynamic load on the amplitude of the first parameter vibration are significant.The influences of linear and nonlinear damping on the maximum deepness of "traction" were discussed.Some typical examples indicate that the dynamic instability behavior of the laminates gradually decreases with increasing delamination,especially,when delamination is close to the mid-plane of the laminates,influence of the delamination on the dynamic instability behavior of the laminates is most remarkable.(3) The nonlinear dynamic stability of piezoelectric smart composite laminates with delaminationA model of piezoelectric smart composite laminates with delaminations was developed and a Mathieu equation considering nonlinear elastic,damping,axial inertia force and electro-mechanical coupling effects was deduced.An analytical solution was given,which can be used to study control effect of the piezoelectric layer.The effects of interfacial debonding length and feed-back control on the instability regions,axial and transverse resonance frequency and the maximum deepness of traction were also discussed.Some typical examples indicate that the dynamic instability behavior of the laminates gradually decreases with increasing interfacial debonding length;However,the effects of feed-back control on the case of laminates with short interracial debonding damage is rather weakness, while for the case of laminates with long length interfacial debonding damage,with increasing debonding length,feed-back control on the laminates could decreases the interaction regions between axial and transverse parameter vibrations.The analysis model,method and numerical conclusions provided in this dissertation should be of great value to researchers and engineers dealing with composite structures.