Partial hybrid stress element for vibrations of thick laminated composite plates

A new element-the partial hybrid stress element-is extended for vibration analysis of thick laminated composite plates. The variational principle of this element can be derived from the Hellinger-Reissner principle to include inertial effects. Equations of motion can then be formulated through variational manipulation. The element stiffness matrix is established by assuming a stress field only for transverse shear, while other stresses are obtained from an assumed displacement field. Traction-free boundary conditions and interface continuity for transverse shear are satisfied exactly. Both consistent and lumped mass matrices are used to investigate the availability of this new element. Examples are illustrated and compared with other published data to demonstrate the accuracy and efficiency of this proposed partial hybrid stress element for vibration analysis.