Objective: Take Ply Drop geometry into consideration during Sequencing. Enforce thicker Laminates in Zones when necessary to avoid excessively long Ply Ramps. Desire is to avoid having ramps from different Zone transitions colliding, and to maintain a reasonable amount of uniform thickness acreage in the Zone.
After determining the optimum Laminate stack per Zone, it is often necessary to compare the thicknesses of adjacent Zones for producibility purposes. Ply Drop locations - i.e. the transition between Zones - should be staggered such that all drops in a transition do not occur in the same place. For example, it is common in the aerospace industry to enforce a 20:1 ramp rate for ply drops across transitions, as shown below.
Enforcing these types of rules necessitates adding thickness in some locations, with the desire to avoid Ply Ramps from different Zone transitions colliding, and to maintain a reasonable amount of uniform thickness acreage in the Zone. For example, in the diagram below, Zone 2 is narrow and there is not much room to ramp down or up in thickness. Minimum manufacturable thickness is greater than mass optimum thickness.
Note
Enforcing Ply Drop Constraints will lead to a heavier overall solution but the part will be considerably more manufacturable and devoid of stress concentrations caused by excessive Ply Drops.
Traditionally, Ply Drop Constraints are enforced by stress or design engineers as a manual post-process on optimum sizing results. But, an algorithm was developed in HyperX to do this automatically during Sequencing.
As this is a process imposed during Global Ply generation, the prerequisites are the same as those for running Sequencing:
Tip
It is highly recommended to run Sizing with more than one Requested Design on the Design Property form. This gives HyperX more options to search through to find a viable, manufacturable solution.
Zone Transitions are entities that, as the name implies, define the transition boundary between two adjacent Zones. They can either be defined manually or automatically generated based on Zone definitions.
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Select all Zones that require the max width condition (recall they must all be in the same Structure).
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From the Composites tab of the Ribbon, select "Zone Transitions" to launch the Zone Transition Form.
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Choose to automatically generate the Transitions for all Zones selected, or to manually define them for yourself.
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Click 'Apply' to generate the defined Transitions. Notice that Zone Transitions are now visible in the Viewport and can be selected. As with all other HyperX forms, any Transition that is selected in the table is also selected in the Viewport for enhanced visibility.
A Ply Ramp occurs anywhere there are drops, or simultaneous drops and adds. Ply Drop Constraints, such as the 20:1 drop rate, are enforced by defining the maximum width of the Ply Ramp. The transition width is calculated by the following:
\(width=\sum_{i=1}^n\left(t_i \times s \right) + \sum_{i=1}^m\left(t_i \times s \right)\)
Where:
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\(n\) = Number of Ply Drops
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\(m\) = Number of Ply Adds
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\(t_i\) = Thickness of Ply \(i\)
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\(s\) = Slope of Ply Ramp
The figure below gives a graphical representation of this width:
Once your width constraints are calculated accordingly for each transition, input them in the Max Width column of the Zone Transition table.
Now that the Max Ramp Width Constraints have been defined, HyperX has to be configured to enforce them. To do so:
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Open the Sequencing form for the concept that defines your selected Zones.
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When the Sequencing form is first open, it performs a “quick” Sequence, which just assembles Plies from the lightest weight solution without trading Laminates. This result may not meet the width requirements. You can view these results in-line with the corresponding width requirements on the Transitions table.
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Open the Sequencing Preferences form (under 'Advanced').
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In the resulting form:
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Set the slope 's' of the Ply Ramp (i.e. 20:1)
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Check "Enforce Max. Transition Width"
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To force the Sequencing algorithm to trade-out Laminate solutions, the slider bar must be set to >0.
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Click 'Sequence'.
To understand the quality of the result generated by the Sequencing process:
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Review the Trial as compared to Baseline in terms of weight and manufacturability metrics.
Note
For Metrics 1, 2, and 3, lower is better.
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Compare the Actual Width column to the Max Width column on the Zone Transition table.
If satisfied with the current solution, click 'Apply' to save the corresponding Plies to your Database. However, it is possible that no solution will be found. Some things to consider:
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Width constraints may be too stringent
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Laminate thickness may vary too much
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Not enough requested designs on the Design Property to evaluate
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Re-Analyze the Structure to generate updated margins with the final Plies.
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Use the Ply Visualization features to view the generated Plies.