Composites

That’s right.  We now have composites in Simulation 2009.  Let’s take a little look at what it can do…

Let’s start with the basics:

Composites can be used for linear static, frequency, and buckling studies.  Up to 50 layers can be specified in any given shell.  Each layer can have a different material assigned.  Isometric and orthotropic materials can be used.  Plies are assumed to be perfectly bonded with no bonding thickness and negligible shear deformation between them.  There are three composite options available:

-          Symmetric laminate

-          Unsymmetric laminate

-          Sandwich composite

The sandwich composite is a three layer composite, two outside skin layers around a core layer.  The skin materials should be stiffer than the core material.

Failure Criterion

Once the composite shells are defined, everything works like any other shell mesh study.  Loads and restraints are loaded exactly the same as always.  The only other thing that changes for the composite study is the failure criterion utilized for a Factor of Safety plot.  I could try to interpret this but I think it would be better to quote the What’s New manual for the next three sentences:

“To determine whether a laminate will fail due to applied loading, the program first calculates stresses in all plies.  It applies next a failure criterion based on these stress levels using a failure theory.  A laminate is considered to fail when at least one ply fails.” (What’s New in SolidWorks 2009, pg.115)

There are three failure criterions that can be used for creating a FOS plot for a composite analysis.  They are Tsai-Hill, Tsai-Wu, and Max Stress.

Tsai-Hill

I spent quite a while looking for a good explanation of these criterion but the best ones that I came across were in the Simulation help file.  For Tsai-Hill:

“This criterion considers the distortion energy portion of the total strain energy that is stored due to loading.  The distortion energy is the portion of strain energy that causes shape change.  The other portion is the dilation energy that causes volume change due to loading.”

Tsai-Hill should be used in situations where the tensile and compressive strengths are equal and the cross-fiber is tensile.

Tsai-Wu

Tsai-Wu is very similar to Tsai-Hill.  The primary difference is that Tsai-Wu takes into account differences between tensile and compressive strengths.  This makes this criterion a little more of a general solution.  The note in the failure criterion selection box states:

“Tsai-Wu Criterion is best applied to composite materials that have inequal strengths in tension and compression AND the cross-fiber stress is primarily in tension.”

Tsai-Hill and Tsai-Wu cannot predict fiber failure, matrix failure, or fiber-matrix interface failure.

Max stress

The Max Stress Criterion should be used when the cross fiber stress is compressive.  From Simulation help:

“Failure occurs according to the maximum stress criterion when the stress in one of the principal material directions exceeds the strength in that direction.  The overall state of stress in the global coordinates is first computed by the program.  Then, the program computes stress along the principal material directions for each lamina by applying a coordinate transformation.”

So which one do I use?

It boils down to this.  If you have compressive cross fiber stress, use the Max Stress criterion.  If you have tensile cross fiber stress, use Tsai-Hill if the compressive and tensile material strengths are the same.  Use Tsai-Wu if the compressive and tensile strengths are not the same.

This wraps up my summation of Simulation What’s New for 2009.  If you have any specific questions about anything that I discussed here, I highly recommend more in-depth examination of the What’s New Document and the help files.  They are great tools.  If you can’t find your answers here, feel free to send your inquiries to support@3dvision.com and I will be happy to see what I can do to provide you with answers.

Back at it with Part III.  Here we go…

Assemblies

They made a nice little change to assembly analysis.  It is now possible to exclude a component from an analysis without suppressing it.  It is also possible to treat components as rigid, flexible, floating, or fixed in space.  Right click on the component in the analysis tree and select the option to apply.

Sheet Metal

Sheet metal components are automatically meshed using shell mesh in 2009.  The shell is created at the mid-plane of the sheet metal part without the user having to create the mid-plane surface separately.  It is possible to switch back to solids by right clicking on the shell in the Simulation tree and selecting “Treat as Solid”. 

Loads, restraints, connectors, and contacts can now be applied directly to the geometry.  The software will automatically apply them to the shell in the appropriate manner.  This includes symmetry.  No more restraining the normal translation and the other two rotations.  Much simpler.  I love it!

Connectors

It is now possible to check the Factor of Safety for Connectors.  Bolt and pin connectors are available in shell analysis studies.  Bolts and pins can also be applied to a mixed stack of solid and shell components.

Mesh

Mesh type is no longer selected when creating a study.  The mesh type that is used for any component can be changed within a study.  When a new study is created, each component defaults to a mesh type based on the geometry.  Structural components default to beam mesh.  Sheet metal components and surfaces bodies default to shells.  Everything else defaults to solid mesh.  Any of these can be changed by right clicking on the component in the Simulation tree and selecting the desired mesh type.  If you have a solid body and you want to treat it as a shell, you are now required to create a surface at the location where you want the shell.

Mesh control dialogue has been updated.  There is a new Mesh Density slider bar that can be used to refine or coarsen the mesh on faces or for entire components.  The option to apply a specific mesh size is still available.

A model simplification tool is built into the mesh menu.  When you right click on the mesh, there is an option to “Simplify Model for Meshing”.  This opens a simplify tool in the task pane.  A simplification factor can be applied to fillets, chamfers, holes, etc.  This is a neat little tool.  I will have to play with it to see what type of job it does.

The last topic that I need to go over is probably the one that everyone is waiting for.  Composites are new in Simulation 2009.  Look forward to an in depth discussion of composites in Simulation in my next entry…  after I do a little research and learn enough to do it justice…