Extended Layerwise Method Of Composite Structure With Piezoelectric Patch

With the widespread applications of composite materials,laminated composite structure is the most common structural form in aircraft,and its analysis and design are paid more and more attention by researchers.Since the damage in the composite materials is very complex and can not be inspected visually,the nondestructive testing(NDT)technology is necessary to evaluate the internal damage.Piezoelectric materials,one of the most popular materials in Structural Health Monitoring(SHM)technology,are used to detect damage in composite structures.Firstly,the potential degree of freedom is introduced into the extended layerwise method(XLWM)and the piezoelectric extended layerwise method is proposed in this paper.The discontinuities of displacements and electric potential resulted from delamination are described in the assumptions along the thickness direction.In the in-plane displacement and electric potential fields,the transverse cracks are modeled by using the extended finite element method(XFEM).The final governing equation of piezoelectric composite laminates is derived from Euler equation,boundary conditions and finite element formula by the coupled electromechanical variational principle.Then,the static analysis method of composite laminates with piezoelectric sensors is established on the basis of the piezoelectric XLWM and the XLWM.The damaged composite laminates are discretized by XLWM the surface displacement degrees of freedom are added to the governing equation of laminated composite plates and piezoelectric sensors,and the final governing equation is derived by using the displacement continuity and internal force balance conditions of the interface between laminated composite plates and piezoelectric sensors.Finally,the static analysis method of composite stiffened laminated plates with piezoelectric sensors and composite sandwich structures with piezoelectric sensors is established based on the piezoelectric extended layerwise method,extended layerwise method and three-dimensional solid finite element method.Thefinal governing equation is obtained by using the displacement equal condition and internal force equilibrium condition of laminated composite plates and stiffener,sandwich structure and upper or lower panels,and the interface between laminated composite plates and piezoelectric sensors.