Promotes design exploration of early concepts and mature structures.

The Exoskeleton tool provides insight as to how the structure may need reinforcing to meet a predetermined performance criteria.

The following optimization types are available:
Provides high-level design direction to determine where the structure can benefit from reinforcing.
If the location is known or the design space location is defined already, use Size optimization to provide design direction more accurately, as it provides accurate diameter and wall thickness as a result.
  1. From the Design Space ribbon, select the Exoskeleton tool.

    Figure 1.
  2. From the guide bar, select Components or Elements to select them from the model.
    1D, 2D, and 3D components and elements are supported.
    Note: Geometry is not supported as a valid input.
  3. Optional: From the guide bar, select Hardpoints to select one or more hardpoints.
    If there is a specific location where the exoskeleton must pass through and be connected, then selecting one or more hardpoints ensures you create the appropriate lattice structure.
  4. Optional: From the guide bar, select Material to assign an existing material to the exoskeleton.
    Selecting a material is optional and can be generated and assigned as a separate post step.
  5. Optional: From the guide bar, select Symmetryto create an exoskeleton 1D lattice structure in symmetry.
    You can define the lattice in symmetry using OptiStruct to ensure a truly symmetric optimization output.
Topology and size optimization examples are illustrated below. The loading conditions consider two simple bending and torsion load cases:

Figure 2.
Topology Optimization
In the figure below, the image on the left illustrates the newly generated exoskeleton (see orange 1D elements). These 1D elements define the exoskeleton lattice design space. The exoskeleton has tied contact defined between the nodal junctions of the exoskeleton (secondary set) and the original structure (main set). One single DTPL design variable is automatically created.
Once the problem is defined, submit the optimization. The output in this case, for topology, removes unwanted design space material that is not required. The image on the right shows the output from the topology optimization for the bending and torsion case. For the torsion load case, it is reinforced near the front shock towers; for the bending load case, it reinforces the structure around the rear door opening.

Figure 3.
Size Optimization
In this example, the location of the design space is known (see the orange 1Ds), however the reinforcement composition details are unknown. The figure on the right (the blue elements) is the result of the size optimization. All beam elements that have little or no influence are manually deleted. The remaining elements provide the necessary design guidance. In this case, it retains the 1Ds that give the largest footprint in that localized area and maximizes the diameter while minimizing the wall thickness (to reduce mass). Results vary depending on the optimization problem definition.

Figure 4.