Hello Everyone,

It is best practice to use the JOIN and EXTRACT tools to create surfaces and boundaries when creating a composite model in CATIA V5, CATIA V6 and 3DEXPERIENCE. This is especially useful for downstream applications.

1. Why is the "JOIN" tool used to create the final surface that forms the shell support of the composite model? 

JOIN is not used just for composites. When creating any surface/shell mesh it is a best practice to always mesh a JOIN. This allows for a more robust and associative analysis in the case where the underlying surface might change. If the surface does change or even number of surfaces changes the mesh will stay connected to the JOIN rather than a surface entity. In addition the JOIN allows the user to easily change the surface direction which in turn adjusts the draping (for composites) and element normal (for analysis. 

2. Why is the "EXTRACT" tool used to create the surface boundary?

EXTRACT is used to determine the ply boundaries. In simplistic cases the ply boundaries match the edges but this may not always be the case. It is a best practice to get in the habit of creating an EXTRACT to locate the ply boundaries. 

Thanks,
Preeti