JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010 - 35

Simulation
manufacturing behaviour of other materials, such as aluminium. Composite design requires a careful balance between the geometric requirements, the material form and the manufacturing process. For example, a monolithic skin panel, a T-shaped stringer and a sandwich panel fairing must be treated differently. Likewise, different material forms, such as woven fabric, unidirectional tape or a non-crimp fabric, all represent unique design and manufacturing implications. Finally, the manufacturing process, such as hand layup, automated tape laying, automated fibre placement, resin transfer moulding (RTM) or forming, needs to be taken into consideration. The specific combination of these variables influences the design approach and, ultimately, the cost and quality of the finished product. Balancing all of these elements constitutes a significant challenge. A solution that incorporates simulation capabilities tailored to the specific material and manufacturing process will provide early visibility into the challenges that will occur during the build process. For example, a machine limitation such as a minimum course length induces a design constraint which can affect ply boundaries, potentially interfere with mating part footprints, and influence part weight. Identification of such constraints must therefore be highlighted and addressed during the design process rather than being left for manufacturers to resolve. Ignoring these critical manufacturing requirements in design will inevitably result in costly design iterations, overdesign, and situations where as-built does not conform to asdesigned, a significant certification risk. By working closely with the manufacturers of automated deposition systems and CAM software for composites, a set of requirements has emerged that enhances the engineering environment so that the design of composite components for automated manufacturing can be fully defined and optimized.

Improving the engineering environment
In an effort to increase throughput, cut production costs and improve quality and repeatability, automated deposition processes are quickly becoming the manufacturing method of choice for composite aerostructure components. Unlike the NC machining of metals or the injection moulding of plastics, manufacturers of automated processing equipment for composites are installing relatively few systems per year as opposed to the thousands being installed for the automated manufacture of other materials. However, some analysts estimate that within the next decade, more than 75% of composite parts will be manufactured with an automated fibre placement, tape laying or robotic deposition process instead of hand layup, which will drive demand for new systems. Regardless of the method, it is clear that we are still in the very early stages of a major transformation in the way that composites are manufactured. Cycle times will decrease significantly, part quality will improve, and design-formanufacturing techniques will evolve to the point where surprises will be rare during machine run time. To keep pace with this evolution, the capabilities of composite design software must likewise evolve. Just as hand layup requires the ability to manage the complex splicing and staggering requirements imposed with fixed-width conventional materials, producibility simulations that mimic hand smoothing techniques and the generation of suitably shaped flat patterns, automated processes will require their own set of innovative design-for-manufacturing capabilities.

The top image shows the ply layup design for a composite fuselage panel generated by VISTAGY’s FiberSIM® software during a CATIA V5 CAD modelling session. The design data is rapidly and seamlessly transferred to CGTech’s VERICUT Composite Programming & Simulation software (bottom) to generate the manufacturing data for the automated fibre placement machine and verify the process.

Minimum course length, staggered ply origins, minimum strip width and minimum cut angles are some of these manufacturing requirements that are part of FiberSIM software. And with the composite manufacturing industry leaning toward machine-independent part definition, additional functions are likely to become part of the design environment. However, a separate category of machinespecific, run-time parameters will still remain part of the offline and machine programming CAM software environment.

Managing airframe assembly complexities
With the increased usage of composites and the ability to tailor thicknesses to support loading conditions, the specification of fasteners is becoming unmanageable. A number of issues, such as material compatibility, hole preparation methods, structural requirements, and cost and lead time implications of specialized fasteners, are raising

No58 June - July 2010 / jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #58 - June - July 2010