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Analysis of piezoelectric composite laminates with edge delamination


Composite piezoelectric laminates play a crucial role in the development of the smart structures technology for aeronautical and aerospace applications, since they combine the mechanical features of the classical laminates with the additional capability to sense deformation and to adapt the structural response accordingly, allowing in this way an efficient structural control, which is achieved by exploiting the features of the electromechanical coupling. In piezoelectric devices the electrical and mechanical loads give rise to stresses whose intensity can be sufficiently high to lead to the failure of the material, especially if damage is present. In this framework, a topic of great relevance is the presence of boundary-layer effects which can initiate edge delamination. This is basically a three dimensional fracture mechanics problem involving an interfacial crack between two anisotropic fiber-composite laminae under mixed-mode loading. In this work a boundary element technique is developed for the analysis of the electro-elastic state in composite piezoelectric laminates subjected to axial, bending, torsion, shear/bending and electrical loadings. The problem is formulated by employing generalized displacements, that is displacements and electric potential, and generalized tractions, that is tractions and electric displacement. This leads to a form of the piezoelectric laminate governing equations that resembles the elasticity notation and is very well suited to obtain the boundary integral representation of the laminate electromechanical response. This formulation is the basis for the numerical analysis of the stresses and strains within the piezoelectric laminate. Numerical results are analyzed in order to evidence some interesting features of the free-edge effects in piezoelectric materials, while application to the edge delamination analysis is discussed.