Usually, a new Layup file is created once a mesh has been finalized in the Patran database. If the user subsequently changes the mesh, the elements in the database and those in the Layup file no longer correspond. This can lead to errors because the elements selected in the viewport may not have the same IDs as those used for internal operations. For this reason, a warning is issued if the database mesh does not correspond to the Layup file mesh when opening a new Layup file.

In addition, it may be desirable to import plies from another Layup file, which may have a different element definition. For example, a draping simulation tool embedded in a CAD package could generate a Layup file which has no knowledge of the analysis mesh.

The Import Ply capability has been developed to allow users to remesh as required and also import of data from other draping systems. In order to do this, it is necessary to generate a mapping between the current mesh and the imported mesh. This mapping is calculated by element matching or piercing.

The MSC.Laminate Modeler first tires to find a direct match between current and imported elements by identifying elements with the same nodal coordinates. Where such a match is identified, the layup on the imported element can be transferred directly to the current element as necessary. The matching process is relatively fast.

Where a current element has no direct match, mapping is determined through piercing. Here, a normal vector is calculated at the centroid of each current element and any intersections with imported elements are calculated. If there are multiple intersections, that closest to the centroid is chosen. The distance between the centroid and intersection point is calculated, as is the angle between the current normal and the normal of the intersected imported element. If both the calculated distance and angle are less than the distance and angular tolerances respectively, the layup on the intersected element is mapped onto the current element. This piercing process is relatively slow due to the multiple calculations required.

In addition to ply import, it is also possible to import a complete composites model definition stored in a Layup file. This will copy the mesh and materials from the Layup file into a Patran database so that further operations like ply creation can be conducted as normal. This feature means that composite models can be transferred and stored by means of the Layup file alone.