Process optimization includes deciding where to begin lay-up, such as in the center of the part or toward an edge. The process planner must also decide which lay-up strategy to use based on surface geometry, such as constant angles or constant curvature. Together, these choices affect fiber coverage and help alleviate potential issues, including fiber overlap where the part is thicker and gaps where the AFP machine can’t place fibers. Process planners must also consider angle deviations and possible effects of steering fibers over distance, such as wrinkling. “The starting point of the lay-up, coupled with the lay-up strategy and coverage, creates an exponential influence on the final manufactured part,” says Harik.
Use of the AFP machine, or its tool path, must also be optimized to reduce inertia and increase throughput. This includes choosing which axis to use and its range of movement. Process planners must think about tow width and whether to use unidirectional or bidirectional fiber placement. “This task is often very, very tedious,” Harik emphasizes.
Using the CAPP tool, process planners begin by entering the part’s geometry and design parameters. Then, they access a menu of preloaded, scored options for each manufacturing decision. With the click of a mouse, they can explore each potential lay-up strategy, including an illustrated analysis of where gaps, overlaps, angle deviations and other defects will occur. The computer-aided tool will not only save time but will also provide traceability and justification for manufacturing decisions.
A modified version of the software that requires less data entry to launch helps designers see how angles, plies, boundaries and other design parameters will play out. “Very often, you see a disconnect between the design and reality,” says Harik. “You can come up with the best design, but perhaps your design is unachievable … or it does not account for how the fibers will actually be laid.” The software will flag potential manufacturing hot spots. For example, if a design specifies a 45-degree ply angle but it will be 40 to 50 degrees in some areas due to geometry or machine limitations, the tool will highlight the discrepancy.
“The software will help designers and engineers make better designs and make manufacturing-informed designs from the get-go,” says Harik. The computer-aided process planning tool is currently in testing and is expected to be released next year.
Advancing Composites in the Construction Industry
Project: Pultruded FRP Construction Framing
School: The University of Notre Dame
Location: Notre Dame, Ind.
Principal Investigator: Kevin Walsh