Improve Predictions, Map Fiber Orientation onto a Structural Mesh
Shawn Wasserman posted on December 11, 2014 |

Why Map Fiber Orientation on Structural Meshes?

If your simulations aren’t taking composite manufacturing into consideration then you’re only getting half the story. The orientation of fiber in a part can have significant effects on the strength and performance of the material. By ignoring the fibers, or assuming a random distribution, you increase the risk of catastrophic failures.

Autodesk’s Advanced Material Exchange allows you to map Moldflow fiber orientation and part characteristics data directly on the mesh. This manufactured information can then improve the accuracy of your FEA simulation.

“Short fiber composites have a significant effect on the performance of the part,” warned Doug Kenik, Product Line Manager at Autodesk. “When the material is injected into the mold, weld lines can be created where two fronts meet due to multiple injection sites or part contours. This will cause a perpendicular and discontinuity rift in the part, a weak area. This part could fail at the weld lines so you must assess the structure at this point.”

Many FEA processes assume random fiber orientation. Unfortunately, assuming a random distribution will make the product act near-isotropic. In fact, fiber orientations will cause a product to act with orthotropic behaviour. This changes the properties of the material and, inevitably, your results.

Advanced Material Exchange Workflow

The Advanced Material Exchange, formally known as project Sundance, is able to incorporate the fiber orientation of a part and apply this information onto the mesh. By doing so, Autodesk reports that results can be an order of magnitude different.

Unfortunately, merging the structural and Moldflow mesh isn’t as easy as it sounds. Moldflow models tend to be optimized to assess warping, wall thickness and the fiber orientation of a molded part. This assessment typically requires a dense mesh. Structural meshes on the other hand look at fatigue, deflection, failure and stress. As engineers typically avoid non-linear plastic responses in FEA, they usually opt for a coarser, faster mesh. The Advanced Material Exchange, however, acts as a bridge between the two.

“The product will take the FEA structural and Moldflow mesh and assess their compatibility for mapping. Usually a structural mesh is much coarser but the Advanced Material Exchange will show you where the structural mesh is too coarse for the fiber map. If this isn’t an area of concern then the engineer can continue. However, if that area is a high stress location then the engineer now knows to rerun the structural mesh,” said Kenik.

 

The workflow is as follows:

  • Import structural and Moldflow models
  • Calculate material model parameters using known material data
  • Align model orientation
  • Assess mapping suitability plot for mesh compatibility, rerun mesh if needed
  • Map Moldflow fiber orientation data onto structural mesh
  • Export structural model into Autodesk FEA software for simulation

The software also uses Mori-Tanaka calculations to translate the composite stress strain curve down to the matrix and fiber level. “Our mapping process is very accurate and efficient so it hardly impacts the solver,” said Kenik. “Using non-linear calculation is much more accurate as the material will behave different at the failure location.”

The Path from Sundance to Product

Like many Autodesk products, the Advanced Material Exchange started as free software through Autodesk Labs. While in the lab, the software was codenamed Project Sundance.

Autodesk Labs allows users to test out software and assess its applications. Software is only available through the service temporarily or until Autodesk has marked the technology for product release.

“We keep it on Autodesk Labs until we have enough data to commercialize the technology,” explained Kenik. “This allows us to innovate and create new ideas and test on the open market with minimal financial risk to users. If we get market validation then we put the product out there.”

Don’t worry too much, though, if an Autodesk Lab project serves a niche market. You might see it again in the app store, on an existing product or available on a subscription basis. With little to risk and much to gain, why not test out other free software on Autodesk Labs before Autodesk commercializes it? Click here to take a look.

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