Composites Modeling – From Black Art to Industrial Discipline
Composites always had a well-defined place in the aerospace industry because of their properties: lightweight to make overall design lighter and toughness to make overall design bear the aero structural loads. At present, from aircraft fairing to train noses, boat hulls and wind turbines, composites offer dramatic opportunities to meet increasing cost-driven market requirements and environmental concerns. However, modeling of composites in a seamless collaborative environment has always been a challenge. This is because of multiple aspects of composites modeling such as design, simulation, and manufacturing that made it quite a tough task on a single platform.
CATIA composites workbench now offers a solution to address various aspects of composites modeling in a unified manner. The objective of this blog post is to provide information on composites workbench capabilities with respect to design, simulation, and manufacturability of composites.
DESIGN IN ANALYSIS CONTEXT
There are different ways to start the preliminary design of a composite part, but the zone-based design is ideal to capture analysis constraints and predict the behavior of the part inside the design environment by importing thickness laws. The thickness laws are calculated as a result of FEA analysis. The composites part design workbench in CATIA provides easy-to-use dedicated zone creation and modification features. Zone-based modeling contributes to significant time savings with the ability to perform concurrent engineering with mating parts. The image below shows a wing panel with a grid created from ribs and spars in assembly context and thickness law for each cell mapped on the grid from a spreadsheet.
Once the grid information is ready, Composites workbench provides highly productive automatic ply generation from zone capabilities with automatic management of the ply staggering and stacking rules. The ability to quickly and automatically transition from zones to plies while keeping full associativity, allows the designer to focus on the design intent and helps dramatically reduce the number of geometrical tasks required to design the part.
To further check the viability of a design from the structural strength perspective, it is possible to perform the FEA simulation within the CATIA environment using the Elifini solver of CATIA analysis. The full associativity with composites workbench is maintained and true fiber angles are taken into account. To address the non-linear aspect of FEA, is it possible to export the plies data in the form of layup files to Abaqus CAE using the composites fiber modeler plug-in. In case design modifications are needed, it is possible to edit and modify any ply or sequence in the composites workbench and instantly export the modified layup file to simulation workbench or Abaqus CAE for validation. Thus designers and analysts can work together in collaboration during the composites development process, saving time, improving product quality, and preventing costly error.
Once the preliminary ply sequence is ready, further optimization of the design can be accomplished by choosing among various algorithms, plies shapes, and customizable drop-off patterns. Powerful ply modification features are also available to tailor the design, whether by swapping ply edges to optimize drop-offs and ply shapes, rerouting sets of plies along a preferred path, easily compute or modify sections of local drop-offs. The image below shows the various options available in local drop-off algorithm of composites design workbench; backslash, slash, socks etc.
DESIGN IN MANUFACTURING CONTEXT
Irrespective of how well the composite panel has been designed, it has to be manufactured in the shop floor in a cost-effective way. To accommodate this reality, certain manufacturing constraints need to be considered at the design phase to prevent costly trials. The composite manufacturing workbench addresses a number of these manufacturing constraints.
The first one to be addressed is the fiber simulation and flat patterns. During the layup process, fiber angles get modified due to draping or wrinkling that takes place while placing plies on a curved surface. The degree of wrinkling is a function of the starting seed point as well as draping direction and order of drape. The composite fiber modeler module simulates the wrinkling by addressing all these draping parameters. The acceptable margins of wrinkle can be defined in the composites material database to display the right producibility pattern.
Once the producibility pattern is obtained, it is further possible to create flat patterns that can be exported to a Nesting application such as Majestic TruNest in compatible format so that ply cutting operations can be performed.
The 3D Splice application is of great advantage in case the material roll width is not enough to cut the entire ply. The splicing application allows you to define cut-outs at various positions and angles and generate flat patterns of individual cut outs. It is also possible to define material access to accommodate trim allowance.
Finally, the ply book application allows you to transfer all the design and manufacturing information on a ply by ply basis to a portable PDF format that can be easily read by shop floor personnel to facilitate ply manufacturing.