Piezoelectric Material
The Piezoelectric Material node defines the piezoelectric material properties either in stress-charge form using the elasticity matrix and the coupling matrix, or in strain-charge form using the compliance matrix and the coupling matrix. It is normally used together with a Layered Piezoelectric Effect multiphysics coupling node and a corresponding Piezoelectric Layer node in the Electric Currents in Layered Shells interface. This node is added by default to the Layered Shell interface when adding a Piezoelectricity, Layered Shell multiphysics interface.
This material model requires one of these products: Structural Mechanics Module, MEMS Module, or Acoustics Module.
When working with layered shells, you almost invariably take the material data from what has been defined using Layered Material Link, Layered Material Stack, or Single Layer Material nodes. It is however possible to override some data from a Piezoelectric Material node too.
In order to have a correct model, all layers must have been assigned material data for all boundaries selected in the settings for the interface. The override rules for the material models in the Layered Shell interface cannot enforce this, in the same way as for other physics interfaces. You can have several Piezoelectric Material nodes with the same (or partially overlapping) geometrical selections, but with different layer selections.
By adding the following subnodes to the Piezoelectric Material node you can incorporate many other effects:
When the Piezoelectric Material node is added to the Layered Shell interface in the absence of an active Layered Piezoelectric Effect multiphysics coupling node, the material behaves similarly to a Linear Elastic Material node. The elastic properties will correspond to the elasticity or compliance matrix entered (see below). The piezoelectric effect is then not included in the equation system.
See also Piezoelectric Material in the Structural Mechanics Theory chapter.
Shell Properties
Select the layer or layers for which this material model is to be used.
When Use all layers is not selected.
Data given in the other sections of this node applies to all layers. Thus, if you enter material data explicitly, rather relying on the default From material option, you will override that material property for all selected layers.
Piezoelectric Material Properties
Select a Constitutive relation Stress-charge form or Strain-charge form. For each of the following, the default uses values From material. For User defined enter other values in the matrix or field as needed.
For Stress-charge form, select an Elasticity matrix, Voigt notation (cE).
For a Strain-charge form, select a Compliance matrix, Voigt notation (sE).
Select a Coupling matrix, Voigt notation (d).
Select a Relative permittivity (erS or erT).
Enter values for the Remanent electric displacement Dr.
Select a Density (p).
Density
If any material in the model has a temperature dependent mass density, and From material is selected, the Volume reference temperature list will appear in the Model Input section. As a default, the value of Tref is obtained from a Common model input. You can also select User defined to enter a value or expression for the reference temperature locally.
Default Model Inputs and Model Input in the COMSOL Multiphysics Reference Guide.
Out-of-plane Material Orientation
The layered material always operates with a boundary coordinate system on the base surface (laminate system). For such systems, the third base vector direction is always normal to the surface. Use a special control available in this section if you need to change the out-of-plane orientation of the material. This is essential if your piezoelectric device requires the pole direction to be tangential to the shell, but the pole direction in the material data coincides with the third coordinate axis - such material orientation is assumed for all the piezoelectric material data available in COMSOL Material Library.
Geometric Nonlinearity
If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. There are, however, some cases when the use of a small strain formulation for a certain domain is needed. In those cases, select the Force linear strains check box. When selected, a small strain formulation is always used, independently of the setting in the study step. The check box is not selected by default to conserve the properties of the model.
Location in User Interface
Context Menus
Ribbon
Physics tab with Layered Shell selected: