Composites Cost Model Enhancements
aPriori 2019 R2 provides a new Composites cost model for estimating manufacturing costs for parts made from continuous fiber-reinforced composite materials. The initial release is targeted at part types, material types, and layup processes common to the aerospace industry. The cost model supports both solid laminate parts and sandwich-structure parts containing honeycomb cores, made with thermoset resin materials (epoxy and phenolics).
Three different Layup processes are supported in this initial release of the Composites cost model:
• Hand Layup – a manual process in which large rolls of pre-impregnated (“pre-preg”) material are cut to produce the final ply shapes; the plies then are placed onto the tool by human operators. This process typically is used for smaller parts which have more complex geometries, such as small radii or bi-directional curvatures that may require darts in the material. Hand Layup also commonly is used for sandwich-structured composite parts which include lightweight honeycomb cores. The aPriori cost model automatically determine the number of hand layup cycles required. A cycle consists of placing some number of plies, then enclosing them in a vacuum bag, applying the vacuum to compact the plies and remove trapped air, then removing or rolling back the vacuum bag to enable placing the next set of plies. This incremental compaction or debulking improves the part’s quality by preventing air bubbles or voids forming within it. A user also may override the aPriori-computed number of hand layup cycles if desired.
• Automated Tape Layup (ATL) – an automated process in which rolls of a uni-directional composite tape material (typically 6 – 12 inches wide) are laid down by an automated head. ATL typically is used for large, fairly flat parts such as wing skins as it is not well-suited for achieving complex geometries or even laying into concave barrel-shapes such as fuselage skins. It also is not well suited for parts with cores since pressure from the machine head may crush the core material.
• Automated Fiber Placement (AFP) – an automated process similar to ATL but uses very narrow rolls or “tows” of tape material (typically 1/8 to ¼ of an inch wide). The machine head can lay down up to 36 individual spools of tape simultaneously, allowing each tow to follow more complex curvatures than typically can be achieved with ATL. It also is not well suited for parts with cores since pressure from the machine head may crush the core material.
Other processes included and costed in the Composites routing are:
• Ultrasonic Cutting (included when Hand Layup is the chosen layup process) – One or more layers of pre-preg material are rolled out onto an ultrasonic cutter bed and a pre-determined pattern of plies are cut from it. Multiple layers can be cut simultaneously if desired to reduce cutting cycle time per part.
• Mold Preparation – estimates the time and cost of (a) applying and curing a mold release agent to the tool, which helps ensure that plies don’t stick to the tool and the part can be removed after curing, and (b) applying and curing a Tool Tack substance to the tool to help the plies stay in place as they are being laid up.
• Autoclave –the part is placed into a chamber which produces and maintains the specific pressure and temperature conditions required to cure the resins within the plies.
• Tool Breakdown – accounts for moving the part from the Autoclave to a bench area, dismantling the final vacuum bag package and removing the part from the tool.
• Tool Cleaning – after the previous part is removed from the tool, it needs to be cleaned in preparation for the next part to be laid up.
• Trim and Drill – the profile of the part is machined with a 5-Axis Mill cost model to produce clean edges on the finished part, and to drill any holes.
• Ultrasonic Scan – an inspection process in which an ultrasonic probe is used to detect defects in the composite part. aPriori provides two types of Ultrasonic Scanning processes: Ultrasonic A-scan, in which the part is submerged in a tank and an ultrasonic probe scans the part surface; and Ultrasonic C-Scan, in which the part is placed between a waterjet and the ultrasonic probe.
• Manual Paint – this process is included automatically since composites parts are usually painted for both cosmetic purposes and for functional purposes such as to provide a moisture barrier and protect the composite from damaging fluids such as hydraulic fluid, fuel and de-icer. The new Manual Paint process cost model is more sophisticated than the existing Painting process. It assumes multiple coats of primer and finish coat, with sanding performed in-between coats, and assumes the use of some paints common in the aerospace industry.
• Final Inspection –a final visual inspection performed in order to detect any defects on the surface of the part.
A unique aspect of the aPriori Composites cost model is that it accounts for how ply geometry and material impacts manufacturability and cost. The apriori algorithm considers the size, shape, curvature, material, and fiber orientation of each ply to determine how this will affect the layup rate for each of the three layup processes.
Supported modeling formats: Note that in industry, there is a wide variety of practices and formats used to model composite parts. In order to cost a composite part, aPriori requires that information necessary to define the ply and core geometry be present in the CAD file (and ideally in the CAD model tree hierarchy itself). The ply and core geometry also must be displayed, not hidden. This is necessary for aPriori to read and determine the size and shape of a ply, which affect both processing time and cost and material cost. aPriori also can read ply and core meta-data from the CAD file in order to determine the specific material used for each ply or core, or the orientation of the ply fibers. These inputs affect both material cost and layup times, as less-flexible materials take longer to lay up. For aPriori to determine material information from the CAD model, this material-related meta-data also must be contained in the CAD model tree hierarchy or in an annotation that is associated with CAD model geometry.
As a result of this dependence on the CAD modeling practice, this initial release of the aPriori Composites cost model will officially support 3 formats for composite parts, which are generated by using the following combinations of CAD system and Composites Design tools:
• CATIA with Fibersim
• CATIA with CATIA CPD/CWB
• NX with Fibersim
Note that there is some capability to cost composite models even when not all relevant information can be read from the CAD model. For example, if ply material cannot be read from the CAD file OR the material can be read but isn’t found in the aPriori material database, aPriori assigns a common material as a default. Users then can assign the desired material to each ply manually.
aPriori also provides a flexible mapping layer to adapt to other modeling practices. If you follow a different modeling practice than those listed above, aPriori still may be able to work with your composites models by developing a new mapping, rather than waiting for a future release of aPriori. Please contact your aPriori account manager to learn more.
Please refer to the Known Issues and Workarounds section below for a description of some limitations in the initial release of the Composites cost model and workarounds.