Nonlinear Delaminated Buckling Near The Surface Of Functionally Graded-piezoelectric Laminated Shells Under Thermaland Electrical Loads

Functionally graded piezoelectric material has been applied more andmore widely in the industry such as aerospace, sensor and active control for ithas the properties of functionally graded material (FGM) and can achievesensing and control through the piezoelectric layer. But because of the defectsin the manufacturing and the low energy impacts during the application,inevitably there will be internal damage, among which, delamination is oneof the relatively more common and serious forms. When the load of thefunctionally graded-piezoelectric cylindrical shells reaches a certain criticalvalue, the delamination may bring about local buckling. Along with theincrease of the load, the delamination will expand, decreasing the strengthand the stiffness of the structure greatly, thereby causing damage to the wholestructure. On the basis of the previous studies, taking the influence oftemperature change on the material properties into account and applying the principle of minimum potential energy, this paper studies the buckling oflocal sub-layer in a symmetric close cylindrical laminated shell under axialcompression、thermal loads and electrical field. The delamination shape ofthe symmetric cross-ply cylindrical shell is assumed to be ellipse、rectangle、triangle and lemniscate near the surface. Under the assumption of plane stressand the classical laminate theory, derived the calculation formula of the totalpotential energy and the buckling equation of the sub-laminated shell. Toaccord with engineering practice more accurately when analyzing thedelamination, the transverse displacement of the sub-laminated shells isthought over. The results show that the pattern of laminated shells、the radiusof the cylindrical shell、the shape and angle of the sub-layer、thermal loadand the electric field all have influence on the local buckling of thesub-layer. And with the increase of the radius-thicknessratio、the increase oftemperature change or the decrease of the electric field,the localdelamination will occur more difficultly. Then the delamination growth andenergy release rate of elliptical and triangular sub-layer is studied and thepossible direction of delamination growth is given. The buckling andextension of sub-layer will result in the decline of carrying capacity. Whenthere is no sub-layer, the critical buckling force of the functionally gradedpiezoelectric cylindrical shell can be calculated. Comparing the results under this condition and the critical buckling force of local buckling, the influenceof sub-layer can be achieved.