Reno Genest
Ansys Employee


Hello Sushil,

You can create abrupt section changes by defining a different number of layers for each oriented element sets. This will lead to ply drop off. Here are 2 ways of doing it:

Splitting the surface in SpaceClaim:

I think the best way of doing it is to slice your surface geometry in SpaceClaim to have all the regions of the surface where you have different layups (different number of plies). You want to split the face without creating new surface bodies:


Then, you create named selections in Mechanical for each region. The named selections will transfer to ACP as element sets. You can then use the different element sets to create the Oriented element sets needed to build the layup. This is the best way because if you refine the mesh in Mechanical, the element sets will update properly based on the named selections in Mechanical. Let me know if you have questions about this process.

Using selection rules:

Using selection rules is the second best option I think. It will keep the regions almost the same when refining the mesh, but you may have some elements that are not picked up by the selection rule and you end up with a jagged region. This may be okay for early design iterations when you don’t know exactly where the boundary of each region will be. So, selection rules is more flexible and allow you to quickly change the boundary of each region.

So, with selection rules you don’t need to split the surface in SpaceClaim and you don’t need to have named selections in Mechanical. I created an example of a square plate with 3 regions (left, middle, and right). Here is the left region selection rule:


Once you created the selection rules, you can create the oriented selection sets:

On the General tab, you select all elements as element set and define the other inputs (point, direction, rosette) as usual. Then, you move to the Rules tab and select the appropriate selection rule for the oriented selection set:


You do the same process for all regions and then you can build the layup (add plies in Modeling Groups):

Then, when you create the solid model, you have drop off options. The default are:

Which leads to the following:

The ply drop offs will happen over the length of your element. So, if you have large elements, the drop off will be smoother and if you have small elements the drop off will be more abrupt.

You can also disable the drop off to get an abrupt drop:


But, this is not a good design; it will lead to stress concentration which is not good for fatigue life. You should have a nice and smooth transition in your composite layup.

I recommend you create a simple plate model like the one above and “play” with the different options and see what works best for you. There are many ways to do things in ACP.


Let me know how it goes.