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08 Jul 2008  -  United States

NIAR's composites lab lay-up room expands capabilities

© NIAR

Tucked away in a corner of the National Institute for Aviation Research’s Composites and Advanced Materials Lab exists the lab’s highly capable and rapidly-expanding lay-up room.

The layup room has existed for several years, and has recently experienced several modernizations and capability and procedure updates under the management of Allison Crockett, NIAR research engineer and program manager.

The layup room’s current workload is made up of about 30 percent from the aviation/composite manufacturing industry and 70 percent from government entities like the FAA and the NIAR-Industry-State (N-I-S) research program.

“That is quickly flipping, because we’re getting more and more companies wanting us to fabricate their qualification or equivalency panels, as they’re having a hard time getting people to do it in a timely manner,” Crockett said. “Every month we’re getting another industry request, it seems.”

Crockett credits that growth in part to several industry courses on composite materials that NIAR and Wichita State University’s College of Engineering have offered over the past four years. To augment lectures on a variety of topics related to composites manufacturing and testing, the classes have always included hands-on training in the lay-up room—and that’s the first time a lot of the industry professionals in the class even realized the room existed, Crockett said.

What they’ve discovered upon arrival is a “clean room” with a large walk-in freezer, the most current bagging materials available, a controlled environment, and vacuum lines throughout the room, to optimize space and time. The lab has two large lamination tables for performing hand lay-up of resin-impregnated fiber forms (prepreg).

Plies are laminated most commonly in an open (one-sided) mold; the plies are then consolidated and “debulked” using a vacuum bagging process with an air-impermeable plastic. The edges are sealed with sticky tape and vented. The air within the plies from lamination process is then removed using a calibrated vacuum port. Next, the panel is cured in NIAR’s 3-foot-by-5-foot research autoclave, which applies temperatures as high as 1000 degrees Fahrenheit and pressure up to 400 psi. Once the part is cooled, it is inspected visually and by NDI for defects and anomalies. Finally, it is cut in the Composites Lab machine shop to the desired specimen sizes for testing in NIAR’s Composites, Fatigue & Fracture and Structures Labs.

“Our panels have come out and they’ve passed C-scans very well, with very few voids,” Crockett said of a recent project. “They’ve undergone testing and the strengths are really high. That would be a by-product of good panel fabrication.”

Other types of lay-up that the staff of four full-time employees and three part-time students does most often are vacuum-assisted resin transfer moulding (VARTM) and wet lay-up. For VARTM, fiber preforms are impregnated with resin inside a closed mould with the assistance of a vacuum. For wet lay-up, fiber preforms are impregnated with resin by hand, using rollers or brushes.

“The wet lay-up is a messier process because during lamination you have to mix the resin part A and B together and then apply adequate amounts to the various layers of fibers placed in an open mould. A squeegee or paint brush with short bristles usually works best to spread the resin mix around wetting each layer of fiber,” Crockett said.

In large part, the wet lay-up process at NIAR is used to perform repairs on panels being tested in FAA programs like “Effect of Repair Procedures Applied to Composite Airframe Structures” and “Aging of Composite Aircraft Structures” or N-I-S programs such as “Repair of Composite Structures” and “Composite Bearing Allowable Baseline.”
“The wet lay-up is one of the most common repair methods used in the field today,” Crockett said.

By client request, NIAR’s layup room has also performed a few other types of lay-up, including resin transfer moulding (RTM) and filament winding. In the filament winding process, a machine passes fiber material through a resin bath just before the material touches a cylindrical mandrel creating a tubular structure which is then oven-cured or autoclaved on the mandrel.

Crockett hopes to be able to perform more of these types of manufacturing processes as well as more of their “specialties” when the Composites Lab gets space at the new National Center for Aviation Training at Wichita’s Jabara Airport. The training centre is scheduled for completion in the fall of 2010.

“The plan is to move the entire lay-up room out to Jabara, where we will to have more than 5,000 square feet of lay-up space, two large ovens, two large autoclaves, a Gerber cutter, a big walk-in freezer and an even more controlled environment with more air filtration,” Crockett said. “We’ll have the capability of laying up three times the number of panels and offering a lot more courses.”

About the NIAR
The National Institute for Aviation Research (NIAR) is a prestigious state-of-the-art aerospace research and development laboratory with global reach and expertise in research, design, testing, and certification. The Institute’s clientele includes many of the world’s aerospace manufacturers, NASA and the FAA. It is the largest aviation R&D academic institution in America. The National Institute for Aviation Research is an unincorporated division of Wichita State University.

Source : NIAR