Size-dependent Pull-in Analysis Of Electrostatically Actuated Composite Laminated Microbeams

Electrostatically actuated microbeams are widely used in MEMS devices and Pull-in behavior is an important characteristic of these structures.When the geometric sizes of MEMS structures decrease to microns or even sub-microns,the mechanical properties vary with the characteristic sizes,i.e.size effect phenomenon.Composite materials are widely used in engineering applications because of light weight and the ease of designing materials and lay-up,so it is essential to conduct researches on size-dependent mechanical properties of composite materials.In this paper,size-dependent Pull-in analysis of electrostatically actuated composite laminated microbeams was proposed based on a new modified couple stress theory for anisotropic elasticity.The main research works of this paper are as follows:The size-dependent models of clamped-free and clamped-clamped composite laminated electrostatic Euler-Bernoulli microbeams with piezoelectric layers attached were proposed based on a new modified couple stress theory for anisotropic elasticity.With the aid of Hamilton's principle,the nonlinear differential governing equations were established and solved by utilizing the generalized differential quadrature method.Numerical analysis reveals that a good agreement exists between numerical results of the present reduced model and those of available literature.Then,the Pull-in voltage of clamped-clamped composite laminated microbeams can be decreased by applying a very small positive voltage on the piezoelectric layers,while the Pull-in voltage of clamped-free composite laminated microbeams can be increased by applying a positive voltage on the piezoelectric layers.Also,the stacking sequences of composite laminates have a great influence on the Pull-in voltage of electrostatically actuated composite laminated microbeams.Furthermore,the size effect becomes remarkable as the beam dimension is comparable to the material length scale parameter.The present model can predict the size-dependent static behavior of electrostatically actuated composite laminated microbeams and provide theoretical guidance for the design of MEMS structures.