Kinematic Drape Restrictions

The draping simulation approach has several restrictions.

  • Ply shapes to be draped must be smooth. Sharp edges and corners probably produce non-acceptable surfaces for the draping process.
  • Surfaces for the draping elements are created from the ply shape node points. Only linear shell (CQUAD4 and TRIA3) elements are supported. In case of high order elements error message “ply does not form single surface” is output.
  • Ply shapes need to be “attached.” Detached elements like islands are not allowed. Ply shape can, however, be constructed from several sets.
  • Draping on continuous shapes like tubes is not supported. One end of the tube would be identified as the external boundary and the other end as an internal hole. Ply primary draping paths are defined until the model edge is found and in case of continuous shapes, stopping criteria is not met, the draping primary paths may cross each other or the surface creation from the FE mesh fails.
  • The draping procedure does not change mechanical properties of the ply. Initially, orthotropic material stays orthotropic. It is assumed that the material transverse direction is perpendicular to the mapped material direction.
  • The fiber slippage is a phenomenon that takes place after the locking limit and is noticeable only at relatively high deformation levels. The fiber slippage is not considered in the draping approach.
  • Ply external boundaries cannot contain narrow gaps. It is recommended that the gap size is two times the draping element size as minimum.
  • Seed point and draping direction should be selected appropriately, that is one should avoid very unstable shapes along the primary draping paths.
  • Seed point needs to be inside of the ply.
  • Only a single ply can be draped at a time.
  • The surface creation fails, if the mesh quality is bad. An error message "Draping stopped, unspecified error" is given. Draping stops next to the problem area so it can be identified.
  • Draping over holes is supported. However, if the shape of the surface is complex, surface creation at the hole may not be perfect. The issue can be overcome by filling the hole by spline surface, draping the temporary ply and importing the draping results to the original ply.