About Analysis Plies

Plies used in the analysis environment are represented using the following key attributes.
These attributes may be subtly different from their equivalents in the design world: Be careful when transferring this information.
This section highlights the differences in definition.

Geometry

The selected ply region must consist of a set of neighboring elements forming a contiguous region.
If several regions are selected, only the region on which the seed point lies is used for the ply definition.
No shell branches (T-sections) are allowed in the selected ply region. 

Draping Direction  

The definition of the top or bottom of a ply is completely independent of the orientation of the selected elements.
Instead, the ply orientation is defined using the Rosette and Seed Point as described below.  

Material  

The ply material contains physical attributes like thickness and maximum shear as well as mechanical properties.  
This is closely analogous to CATIA materials.  

Rosette  

The rosette (a coordinates system referenced by a ply) defines the basic orientation of a ply.

• The application direction is in the negative Z-direction of the rosette and represents the default direction for adding the ply to a surface.
• The reference direction is in the positive X-direction of the rosette.

At the seed point, the application direction should be roughly normal to the surface and the reference direction should be roughly parallel to the surface to prevent ambiguity in the orientation definition.

Tip: To handle the possible mis-orientation of CATIA draping direction and rosette z-axis, apply the analysis ply on the opposite side of the surface in the layup definition.

 

Direction  

The principal warp axis of the material on the surface can be rotated from the projected reference direction by inputting a non-zero reference angle.
This rotation is counterclockwise when viewed along the application direction.  

Note that in the analysis world, this can be any real value and is not restricted to predefined values as in CATIA.  

Seed Point  

The seed point defines the starting point of the drape simulation process.
It is analogous to the point at which a ply is first attached to a mould surface during manufacture.
As the distortion usually increases away from the seed point, it is best to begin draping near the center of a region to minimize shear distortion.  
If the seed point coordinates do not lie on the selected ply region, the seed point is projected onto the surface along the application direction vector.
The start point must lie on the selected ply region.  
In the analysis world, a seed point always exists.
If producibility parameters are not defined in CATIA, the seed point is defined using the following rules:

• If the rosette origin lies above the ply region, this is used.
• Otherwise, the centroid of the element whose normal is most closely aligned with the z-axis of the rosette is used.  

Stacking  

The equivalent to the CATIA stacking is a layup, which is also a list of plies in chronological sequence of application.
However, in the analysis world, plies can be used more than once in a layup, to make more efficient use of data.
Also, the draping direction of a ply can be modified at this point.