Linear thermal expansion coefficient (3D fiber) (overmolding) results

The Linear thermal expansion coefficient (3D fiber) (overmolding) results can be used to help predict part shrinkage that may occur in the overmolded part, as a result of the temperature changes.

Mesh type:

• 

Analysis sequences that include:

• Overmolding Pack

To create these results, the Fiber orientation analysis if fiber material option must be selected, and a material with filler or fiber data must be chosen. This option can be found on the Fill+Pack Settings page of the Process Settings Wizard.

The CLTE is calculated at every node, through the thickness of the part, for the duration of the analysis, using the fiber orientation tensor at that node. Therefore, each node in the model will have its own thermal expansion result. These results are used by the CRIMS shrinkage correction model and the uncorrected residual stress model. You can view the expansion coefficient at each node by animating the default contour plot, which will animate the result through the part.

• Linear thermal expansion coefficient in first direction (3D fiber) (overmolding)
• Linear thermal expansion coefficient in second direction (3D fiber) (overmolding)
• Linear thermal expansion coefficient in third direction (3D fiber) (overmolding)

Tip: These results are not shown by default. To view these results, click (Result tab > Plots panel > New Plot) and select them from the list of Available results.

Important: If you don't see these result, check that you have a shrinkage model selected. Click (Home tab > Molding Process Setup panel > Process Settings) and click Advanced options. Click Edit associated with Molding material and select the Shrinkage Properties tab. Select a shrinkage model.

Orthotropic assumption

The thermo-mechanical property calculation for fiber-filled composites is based on the orthotropic assumption, that fiber-filled material properties are different in three orthogonal principal directions. Under this assumption, there are 9 independent mechanical constants and three independent thermal expansion coefficients.

The Orthotropic set option is set by default and selects the 9 mechanical constants (E1, E2, E3, v12, v23, v13, G12, G23, G13) and 3 CTE’s (thermal expansion coefficient in first/second/third directions) all at once. In a Fiber analysis, the complete set of thermo-mechanical properties with orthotropic assumption is necessary for a Warp analysis. These properties are element-based, so each tetrahedral or beam element has its own orthotropic set of properties.

Note: To access the Orthotropic set option ensure you have selected an analysis sequence that includes Fill+Pack.

1. Click Home tab > Molding Process Setup panel > Process Settings.
2. If necessary, click Next until you reach the Fill+Pack Settings page of the Wizard.
3. Select the option Fiber orientation analysis if fiber material, and then click Fiber parameters.
4. Click Composite property calculation options, and then from the Fiber-filled property output drop-down list, select Orthotropic set.

Using these results

Compare the results in each of the different principal directions. The material should expand less in the direction of flow (first principal direction) than perpendicular to the flow direction (second principal direction). If the molecules are aligned in the first and second principal directions, then the linear thermal expansion coefficient will be different in each principal direction. If the molecules are randomly aligned, you would expect to see a uniform linear thermal expansion coefficient in each principal direction.

Tip: Click (Result tab > Plots panel > New Plot) and create this result as an XY or Path plot also so that you can view the linear thermal expansion coefficient at a particular element.