JEC COMPOSITES MAGAZINE - Issue #48 - May 2009 - 37

Engineering determined separately and independently by manufacturing software. For example, a machine limitation, such as minimum course deposition, induces a design constraint which can impact ply contour and stagger layout, or interfere with a mating part footprint and modify part weight. Such constraints must therefore be made an integral part of the design parameters and cannot be left to manufacturing to deal with down the line due to the risk of unforeseen and costly iterations or uncontrolled over-design. By working closely with the manufacturers of fibre placement machines, tape laying systems and CAM software for composites, a set of requirements has emerged that enhances the designer’s environment so that he or she can fully define and optimize the design of composite components or assemblies for automated manufacturing. Minimum course length, staggered ply origin, minimum strip width and minimum cut angle are some of these manufacturing requirements that are part of FiberSIM software. And with the composites manufacturing industry leaning toward machine-independent composite part definition, additional functions are likely to become part of the design environment, while machine-specific parameters will remain part of the offline and machine programming software. cascading impact of a skin thickness change and a substructure shift in the fuselage panel. In engineering design, such a change may affect laminate stackup, ply drop-off locations and shapes, the skin inner tool surface, the substructure mating surfaces, fastener specifications, and, ultimately, weight and balance. In manufacturing engineering, the change may affect the ply layup tables, the bill of material, the supplier build-to packages, the maintenance and service documentation. In manufacturing, the change may affect the fibre placement programs, the composite flat patterns, the automated drilling and fastening program, the laser projection files and the process plans. In tooling manufacturing, the skin IML tooling and the substructure tooling may change. Finally, the First Article Inspection plan and other QA documents might change as well. The key issue is not so much that the implications of a single change are many, but that it takes only a couple of inconsistencies or missteps in the change process to derail a whole development programme with extremely detrimental consequences. Getting the change process right requires a combination of expertise in design, analysis, manufacturing and process planning, all within the context of a composite materials environment. Since its inception, Vistagy has embraced the necessity of intelligently automating the recognition and management of design changes as it has developed successive generations of its design software for composites engineering and manufacturing. Quantifying engineering complexity It is interesting to note that “engineering complexity” can be attributed a somewhat specific meaning in design and can be quantified to some extent. Indeed, we attempted to quantify the level of complexity of large aerostructure panels made of composites. For example, for a fuselage panel typical of a commercial aircraft made up of 6 by 8 bays separated by stringers and frames, we obtained the numbers shown in Figure 2. Geometry references are typically created and maintained by the CAD system. Detailed geometry elements are typically created manually and not subjected to any validation in 3D CAD. Beyond the geometric data, there are a staggering 11,320 nongeometric characteristics for the composite skin and 48,300 non-geometric characteristics for the assembly, fasteners and holes. These are not part of the 3D CAD model or in PLM and are not structured. In addition, the relationships are typically not captured in 3D CAD or PLM, nor is the specialized design intent. In all, over 90% of the data is not captured and managed effectively by the CAD and PLM systems. With Vistagy software for composites aircraft development, 100% of the product definition is captured and managed effectively, 85% of the geometry is automatically created and 100% of the critical characteristics are automatically validated. Accommodating change The face of the aerospace composites industry is changing rapidly under pressure from globalization, the emerging markets and the current economic downturn. In particular, manufacturing automation is becoming pervasive in aerospace composites, with the production of ever-larger and more complex composite aerostructures. As a result, aerospace firms need to take a more comprehensive approach to the design and manufacture of composite parts and assemblies. Efficient composites engineering tools extend beyond CAD, PDM and CAE to encompass a composites engineering-specific view of the ontology, process and product details. Ultimately, the foremost challenge facing designers and manufacturing engineers is the need to recognize and be able to rapidly accommodate the inevitable changes that occur throughout the development process without errors and costly delays. As the role of composites continues to evolve, Vistagy and its partners are committed to setting the standard for delivering solutions that will empower aerospace firms to continuously streamline and enhance the design-to-manufacturing process. Cascading impact of design changes Design changes are ubiquitous and inherent to the engineering process. What is the impact of a design change? Consider the More information: www.vistagy.com No48 May 2009 / jec composites magazine 37

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JEC COMPOSITES MAGAZINE - Issue #48 - May 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #48 - May 2009