Enhanced interface stress analysis of piezoelectric smart beams

Piezoelectric patches are usually externally bonded to host structures as sensors or actuators. The performance and integrity of this type of smart structure are determined by the interface stresses within the adhesive layer. To accurately evaluate these interface stresses, a novel analytical model is developed in this study. This new model treats the adhesive layer as two normal spring layers interconnected by a shear spring layer. The peel stresses along the top and bottom surfaces of the adhesive layer are assumed to be different. An interface deformable beam theory is used to describe the deformation of the piezoelectric patch and the host beam. Unlike existing elementary beam theories, this new beam theory captures the deformation of adherends induced by interface stresses by using two interface compliances. Closed-form solutions of interface stresses with enhanced accuracy have been successfully obtained by the new model. The new solutions not only satisfy both the equilibrium condition of the adhesive layer and zero-shear stress boundary condition at the free edge, but also correctly give two different peel stress distributions along the interface between the piezoelectric patch and adhesive layer and the interface between the adhesive layer and the host beam. A numerical example of the sensing charge output suggests that the present model is applicable to the cases of a thick adhesive layer or thick host beams, while the existing model is not.