SAAM Group

8-node Shell FE for Damped Composite Shell Structures - "Integrated Damping Mechanics Models and Shell Finite Element Enabling Predictions of Passive Damping in Laminated Composite Structures"

An 8-node specialty damped shear shell finite element was developed for predicting the damping of laminated composite structures of arbitrary laminations and shapes. The FE encompasses a series of mechanics models enabling integrated modeling of damping from ply to structural level. Evaluations of the developed FE with results from other FEs, analytical solutions and conducted experiments have demonstrated its excellent performance, accuracy and unique predictive capabilities.
Predicted effect of lamination on the first modal damping of a [θ/90+θ/45+θ/-45+θ]S Gr/Epoxy free-free beam.	Effect of curvature angle on modal loss factors of a simply supported Gl/Polyester Cylindrical panel.
Related Publication(s): Plagianakos T. S. and Saravanos D. A., "Mechanics and Finite Element for the Damped Dynamic Characteristics of Curvilinear Laminates and Composite Shell Structures", Journal of Sound and Vibration, in press.

Shear Beam FE for Damped Tubular Multi-Cell Composite Blades
A 3-D specialty beam finite element is developed for the damped structural analysis of composite blades with multi-cell hollow tubular laminated sections. The element encompasses a series of unique integrated mechanics models enabling synthesis of damping, stiffness and mass matrices from the composite ply, to cross-sectional and finally to the structural level.
The new beam element yields very good predictions of modal damping and natural frequencies for the fundamental modes of vibrating beams and wind-turbine blades. All these, at a fraction of the computational cost required by detailed FE analysis using either specialty in-house damped shell elements, or commercial shell elements (modal frequency predictions only). Some detailed FE blade models which are used to compare the performance of the new beam FE are shown.	Wind Turbine Blade Model
1st Edgewise Mode of Uniform Airfoil Blade Predicted Using an in-House Damped Shell Element	Wind turbine

Plate FE for Laminates with Constrained Viscoelastic Damping Layers and/or Sandwiched Foam Cores

Shell FE for Composite Structures with Passive (resistive shunted) Piezoelectric Layer Networks - "Hybrid Multi-Damped Composite Laminates with Shunted Piezoelectric Layers"
The passive damping of hybrid (composite + piezoelectric) structures is enhanced by shunting the piezoelectric layer. In this manner, part of the elastic energy of the structure is converted to electric energy in the piezoelectric layer and finally dissipated in the shunting resistance. A laminate mechanics formulation and a novel plate finite element encompassing damping contribution of both viscoelastic composite plies and shunted piezoelectric layers is developed and experimentally validated.

Effect of ply angle on the fundamental modal damping of a [θ/90+θ/±45+θ]S cantilever beam with a shunted piezoelectric patch.
Related Publication(s): Plagianakos T. S. and Saravanos D. A., "Hybrid Damped Composite Plates with Viscoelastic Composite Plies and Shunted Piezoelectric Layers", AIAA paper 2002-1364, 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference - 10th Adaptive Structures Conference, Denver, Colorado, April 22-25, 2002. Plagianakos T. S. and Saravanos D. A., "Hybrid Multi-Damped Composite Plates with Viscoelastic Composite Plies and Shunted Piezoelectric Layers", to appear in the Journal of Intelligent Materials Systems and Structures.