Free Vibtation Of Composite Structures With Interleaved Viscoelastic Damping Layer

Structural vibration and noise will be produced by external excitation. The usage ofdamping technology for vibration and noise reduction is an effectively and widely usedin various industrial aspects. Composite structures with interleaved viscoelastic layersnot only have higher ratios of strength/density and stiffness/density, but also haveperfect damping properties. With the extensive usage of composite materials,viscoelasitc damping structures composed of anisotropic materials and viscoelasticmaterials have become a new research hotspot. It is anisotropic and can be designed, forthe surface layers of composite materials with interleaved viscoelastic damping iscomposite laminates. Composite materials with interleaved viscoelastic damping layerin the mid-plane may have better damping performance. It means practical to analyzeand calculate the natural frequency and loss factors of free vibration of the structures.In this paper, the natural frequency of free vibration of anisotropic single-layerplates and composite laminated plates is analyzed and calculated. The natural frequencyof free vibration and loss factor of composite materials with interleaved viscoelasticdamping layer in the mid-plane is theoretically analyzed and numerically calculated.According to the classical laminate theory, the natural frequency of free vibrationof single-layer anisotropic plates is calculated. The general frequency of flexuralvibration of orthotropic rectangular plates is solved with simply supported, clamped andfree edges. The different vibration functions are involved into strain energy and kineticenergy with different boundary conditions and natural modes. The frequency of flexuralvibration of orthotropic rectangular plates with different boundary conditions isobtained using Rith method.Normal and shear strains of composite laminated plates are formed using ahigher-order displacement mode. The corresponding stress is found out according to theconstitutive relations. The strain energy and kinetic energy of composite laminatedplates are obtained. The governing equations will be derived by variations ofdisplacement components through the Hamiltonian principle. The natural frequenciesare acquired for simply supported angle-ply laminated plates.Free vibration of a three-layer composite materials with interleaved viscoelasticdamping layer in the mid-plane is analyzed. The surface layer can be either isotropic materials or composite laminates. The displacement of the surface layer is expanded bytrigonometic series, while the displacement of the viscoelastic layer can be indicated bythe displacement of the surface layer. Therefore, the strain energy and kinetic energy ofthe plate can be obtained. The governing equations will be derived using variations ofdisplacement components through the Hamiltonian principle. The natural vibrationfrequency and loss factor can be finally derived.