FiberSIM® Provides Orderly Process for Designing Complex Laminates
Developing an efficient workflow for designing complex laminates is a critical step in being successful in the composites Industry. The FiberSIM® Advanced Composite Engineering Environment™ (ACEE) provides all the functionality required for designers to start with stress analysis gauge thickness data, and interpret it into a complete, sequenced laminate design.
The ACEE starts with a zone-based approach, where constant-gauge regions are defined via Laminate/Material Specification as having set quantities (layers of coverage) of particular materials at particular orientations.
Because many users work with complex designs with highly refined ramp cross-sections, it is preferable to start with a design that’s as flexible as possible. To do this, we recommend that the laminates’ Drop-Off Order Pre-Sorting option be set to No Pre-Sorting on the “Advanced” tab. This can be changed later, but it generally allows for the greatest ease in manipulating ramp profiles, as we will soon see. Next, the default Stagger Profile used when running the Zone to Layer Analysis must be set to Linear Ascending in order to take full advantage of the layers’ Drop-Off Order functionality later.
Once these data are input, users can generate layers by running the Zone-to-Layer Analysis. If users are provided with laminate family or load schedule data from their stress analysts, they will often have full prior knowledge of which layers of specific material and orientation cover which zones, and in what particular sequence. This information can be input as Step values into Material Specifications in FiberSIM prior to running the Zone to Layer Analysis. Doing so will obviate the need to resequence layers later.
Shown below is an example of the default layer sequence FiberSIM produces without prior Step information entered into the Material Specifications. It can be considered a rough “first pass” at the part’s ultimate cross-section. We will refine this cross-section more and more throughout this article.
Note that in the example above, there are four distinct layer families. These “families” have unique zone groups or geometric coverage, but not necessarily the same material/orientation. Even though the layers within each family cover the same zones, they have different shapes due their drop-offs forming ramps rather than block-like steps.
The desired cross section is shown here:
The first step in establishing this cross-section is to sequence these layers. Sequencing is important because it defines where each layer family member (of specific material-orientation) appears in the overall layup order, relative to one another and to members of other families. At this point, the names of layers and the precise shapes of ramps are not critical.
Using the Composite Sequence Manager, users can drag and drop layers in sequential order, while visually inspecting them on-screen. It is important to realize that sequence does not actually influence the order that layers consume the drop-off curves of the zone transitions. Again, establishing a proper sequence defines where material/orientation-specific layer family members are laid up relative to one another, but actual ramp cross-section shapes will be defined later.
With this utility, we start with the default Zone to Layer cross-sectional profile below.
This profile illustrates the Linear Ascending pattern assigned to the default stagger profile used by the Zone to Layer Analysis. Within each layer family, the shapes get larger as they are laid down in sequence.
After using the Composite Sequence Manager to drag the appropriate members of each layer family to their desired locations in the layup, the new cross-section should appear as below.
Please note above that while the layup is looking far closer to the desired cross-section than the default results from the initial Zone to Layer Analysis run, the ramp shapes still need modification. Layer shapes within the same family are still consuming drop-off curves in a Linear Ascending fashion. Again, it is important to emphasize that layer sequencing is independent of ramp profiles.
To create the desired ramp geometry, users must establish a global cross-section by assigning drop-off orders to layers.
The absolute value of a layer’s drop-off order is not as important as its value relative to other layers. FiberSIM assigns offset curves within a zone transition to the layer’s based on their relative drop-off order values. Please see below for examples of this behavior.
Users can manually assign drop-off orders by modifying layers directly and inputting the values. Alternatively, designers working with their own proprietary stacking tools can use the Preliminary Design Interface to export the layer list to their utility/program, then re-import the list with newly-specified drop-off orders back into FiberSIM.
Further, FiberSIM 2009 has the added ability to assign all layers’ drop-off order values at once by specifying a Global Stagger Profile in the laminate. Users can choose from among eight different ramp shapes used commonly in composites design. FiberSIM will automatically assign drop-off orders to maintain a particular (selected) cross-section shape within each layer family.
The table below shows the appropriate drop-off order values needed to achieve the cross-section we want for our example part.
Please also be aware that if too many undesirable layer boundary crossings are encountered, users can change the laminate’s drop-off order pre-sorting setting to Zone Count or Zone Area to achieve different ramp shapes.
Finally, once cross-sections are refined globally by Drop-Off Order settings, users can affect local ramp changes (individual zone transitions) by creating custom stagger profiles. These objects, when assigned to a particular zone transition, override the layers’ drop-off order values at that transition. A custom stagger rofile simply lists in sequential order the curves to consume first. So, for example, a custom stagger profile with a custom pattern “4, 0, 1, 3, 2” would specify that the first layer (sequentially) using the zone transition with this custom stagger profile assigned to it would use the fourth offset curve in the transition; the second layer would use the transition’s base curve;the third would use the first offset curve; and so on.
In lieu of entering all these values, designers can use the Visual Stagger Editor to establish this custom pattern by modifying a zone transition, assigning it a custom stagger profile, and going to the “Visual Stagger Editor” tab. The user can drag and drop layers to establish the customized ramp profile they would like.
As we’ve seen, the FiberSIM Advanced Composite Engineering Environment contains the tools necessary to capture the top-down design intent designers need to create complex composite parts efficiently. Ultimately, by sequencing the members of layer families appropriately, then establishing a desired cross-section—globally using drop-off orders, then locally using custom stagger profiles—nearly any layup can be achieved.
If you have any further questions regarding the interaction between layer sequencing and drop-off order, please do not hesitate to contact the VISTAGY Product Support team:
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