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# How to Resolve Ply Producibility Problems in Fibersim

Community Manager

When attempting to resolve producibility problems with a given ply in Fibersim, you have many options outside of changing the basic surface geometry:

1. Change the propagation settings – while this may help, it is critical that the propagation settings match the layup procedure on the shop floor to ensure an accurate flat pattern.
2. Move the origin – this frequently has the largest impact, though may not be feasible on the shop floor.
3. Splice the ply – smaller pieces will usually drape more easily, but this may not be allowable from a stress or weight perspective.
4. Dart the ply – darting may not be an option in critical areas

Assuming you have already ruled out 1 through 3, the question becomes: “How do I apply darting to this particular ply?”  It turns out that Chapter 2 of the Fibersim user guide actually has a wealth of information on how to interpret producibility and apply darts based on the type of wrinkling encountered.  It can be found with your Fibersim installation (%FIBERSIM_HOME%\FiberSIM\documentation) or by accessing the help menus via the UI.  Some highlights:

Determining deformation type (Wrinkling vs. Bridging)

1. Trace a line from the ply origin through the deformed cell
2. If the deformed cell elongates along that line, it is a wrinkling condition, caused by too much material
1. Apply a slit dart to remove excess material
3. If the deformed cell shortens along that line, it is a bridging condition, caused by not enough material
1. Apply a V dart to allow material to open up around the problem area

Remember, the dart type refers to its 3D shape, which actually has an inverse relationship to its 2D shape:

• A Slit Dart is a 3D slit, but will typically be an open V shaped cut in the flat pattern.
• A V-Shape Dart is an open cut in 3D that must be patched, but will manifest in a 2D slit in the flat pattern.

Effective Slit Dart depth

1. Find the first non-red fiber path on either edge of the red region
2. Trace them back away from the boundary to find the intersection
3. Use the intersection as a starting point for your slit dart

V-Shape Darts

For V-Shape Darts, the best practice will depend on the design limitations you have.  Since you are effectively removing an area of ply coverage, a patch will likely need to be created to fill it, which may necessitate enlarging the area to make the patch structurally viable.  This makes it impossible to provide a generic guideline for effective sizing.  Just make sure that the resultant flat pattern doesn’t overlap itself!

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