Engine Structures Next Target For OPM’s 3D Printed Composites
March 1st, 2017
Aerospace manufacturers have long used polymer 3D Printed for rapid prototypes or lowstrength production parts such as ducting, but the need for load-bearing structural components has pushed the industry to qualify metal additive manufacturing processes using highstrength alloys.
But just as reinforced composites have grown in capability over the decades to gain a major share of airframe structures, polymer additive manufacturing is evolving. Oxford Performance Materials (OPM) has secured a Boeing contract to supply 3D Printed components for the CST-100 Starliner manned spacecraft that are large, complex, composite and structurally loaded.
“Some parts are highly loaded,” says Bernie Plishtin, chief business development officer. The company’s OXFAB additive manufacturing process uses a high-performance thermoplastic, polyetherketoneketone (PEKK), reinforced with short carbon fibers. OPM says it is the first to apply 3D Printed to PEKK, which has high resistance to heat and can withstand high mechanical loads.
South Windsor, Connecticut-based OPM uses carbon fiber from Hexcel, and the composite materials producer has invested an additional $10 million in the company, taking its total to $25 million. “Hexcel’s follow-on investment will further enable OPM to expand capacity to meet rapidly growing market demand . . . in aerospace and other industries,” the company says.
OXFAB parts will be used in three areas within the CST-100, which is designed to carry up to seven crew to low Earth orbit. One is the air revitalization system, says Plishtin. OPM has begun shipping production parts to Boeing for installation in the spacecraft, which is scheduled for its first unmanned orbital test flight in June 2018, followed by a crewed flight in August 2018.
“From our earliest discussions with Boeing, they stressed the need to see significant reductions in weight, cost and lead times in order to consider replacing traditional metallic and composite parts with a new technology for their space program,” says Larry Varholak, president of OPM Aerospace and Industrial, the company’s 3D Printed unit.
“Boeing has demanding requirements for manned spaceflight. We worked with them for many years and met every test point to get on the Starliner. But that just gets us past the performance part,” says Plishtin. “The real benefit is in time to delivery, cost reduction and the ability to address design changes quickly.”
Introducing chopped carbon fiber into the PEKK “alloy powder” significantly reinforces the thermoplastic and makes the material conductive. Components are 3D Printed by laser sintering—melting the powder with a laser beam to produce a part layer by layer—and the material is “machine agnostic,” he says. So far, the technology has been qualified with one manufacturer’s laser sintering machine.
With 3D Printed, complex parts can be produced without tooling or touch labor. “We can comingle shape and complexity with no negative consequences,” Plishtin says. OPM also recycles the unused powder to reduce cost. “Only 10-12% of the powder in the bed is used in each run. The other 85%- plus is unused powder that we can recycle,” he says. OXFAB is qualified for one recycle, but OPM is working with a “major prime” to qualify the material to be recycled up to three times, and possibly more. “The second recycle will be qualified within this quarter,” says Plishtin.
The next step is to apply OXFAB to commercial aircraft, and the company is initially targeting thrust-reverser cascades and fan exit guide-vanes on turbofans. “These are secondary structures that are loaded, and historically have tremendous touch-labor content,” he says. “We can replace a hand-layup composite cascade for a 50% reduction in cost in part by eliminating that labor.”
OXFAB® - Ni Plated ESD Fan
Exit Guide Vane (22”H)
In addition to eliminating hand layup and reducing the raw material required, 3D Printed removes the need to machine the cascade to its final shape. “We just machine the attachment holes to the positional tolerance,” Plishtin says, adding that cascades can be produced as a single part, eliminating attachment hardware, and they offer weight savings over aluminum or magnesium castings.
“We are talking to engine manufacturers,” he says. OPM is developing technology to nickel- plate the fan exit guide-vanes for erosion protection. “We can 3D Printed a six-pack of vanes as one part and nickel-plate the entire structure.” Plishtin says the 3D Printed structural vanes have the density of aluminum and mechanical properties “between titanium and the highestperformance aerospace aluminum.”
OPM uses Hexcel’s AS4 carbon fiber but is now working to incorporate the company’s IM intermediate-modulus and HM high-modulus fibers into OXFAB . “We have aggressive research and development spending,” says Varholak. The company is also gearing up for high-volume 3D Printed of engine components. “We have nine machines and are facilitized for 40. We are growing rapidly,” he says.