The aerospace industry continues to increase its use of composites, a phenomenon that’s pushing academics, trade groups and manufacturers to research and develop methods to enhance the techniques and tools for using the materials.
Some of those advances include improvements in the composites themselves, but others involve enhancements in manufacturing machinery; the software used for machine control, and also for simulation; assembly techniques; and inspection equipment.
What’s driving these improvements?
Just as in the automotive industry, lightweighting is the Holy Grail for aerospace. Lighter vehicles, whether on the roads or in the air, use less fuel and reduce carbon emissions. In addition to improved performance and fuel savings, though, composites offer the added benefit of resisting corrosion.
As a result, the growth in the use of composites is expected to be high at least until 2033, with a valuation at that time of $6 billion and consumption at 134 million pounds, according to market research firm Lucintel (Dallas, TX).
“Composites consumption in the commercial aerospace industry will be driven by three programs, Boeing 787, A350 XWB, and A380,” according to Lucintel’s web site. “Both Airbus A380 and (Boeing) 787 contain more than 100,000 pounds of composites per aircraft.”
The use of carbon fibers to strengthen composites is also expected to grow as a result of increased use in the automotive and aerospace industries, among others, said R. Byron Pipes, director of design, modeling and simulation technology at the Institute for Advanced Composites Manufacturing Innovation (Knoxille, TN), a public-private partnership to increase domestic production capacity, grow manufacturing and create jobs across the composite industry in the United States.
“We use 100 million pounds of fiber now,” he said. “If we commit to a composite automobile, we’ll be using a billion pounds of fiber.”
Lou Dorworth, division manager for direct services at Abaris Training Resources (Reno, NV), referring to the growth in the use of automated fiber placement and tape layup machines, said: “Ten years ago we probably would have a laydown rate that’s 50 percent less than today due to application of automated layup methodologies.”
“By combining those two technologies in one machine, that has been a big plus in automation,” Dorworth said.
Robotics and automation are on the mind of more than one expert.
“There are and will be a lot more robotics and automation to get rid of the labor intensive processes, for one,” said Scott Beckwith, global technical director for the Society for the Advancement of Material and Process Engineering (Diamond Bar, CA), although hand layup will not likely ever completely go away.
“There are some things like tight 3D geometries that can’t be done with automation, such as some of the very complex resin infusion processes,” Beckwith said.
Beckwith also sees opportunities for the aerospace industry to learn from the automotive industry, and vice versa. Bringing the two industries together to share information is something his society facilitates.
“The automotive industry has learned how to work with snap cure, or rapid cure, resins and processes that work in minutes vs. hours and that looks very attractive to the aerospace people,” Beckwith said. “And the automotive companies are just learning how carbon fiber works with certain resin systems that aerospace has been using for a long time.”
Unlike the automotive industry, and despite the growing use of robotics and automation, aerospace continues to employ labor-intensive processes on the shop floor.
“It’s just not economical to build the small parts in aerospace in an automated fashion,” said Dorworth. “When it comes to laying up by hand, which is not going away, the biggest benefits we’re seeing are the inclusion of laser projectors and instructions that are projected onto the layup for the operator.”
Dorworth was referring to Assembly Guidance, a Massachusetts company that’s made innovative use of lasers in the composite assembly process.
A ‘template of light’
In the mid-1980s, the aerospace industry was searching for a replacement for the complicated, expensive templates used to locate composite materials to make airplane parts. Made of Mylar or fiberglass, the templates could cost tens of thousands of dollars apiece for large parts.
“There were people who said you could probably project a laser to create a ‘template of light’,” said Scott Blake, president of Assembly Guidance (Chelmsford, MA), who at the time was involved with laser light shows in the entertainment industry. “I knew how to draw pictures with lasers, but they weren’t very precise.”
Blake figured out how to incorporate lasers into the composites laminating process, and today his company integrates its LaserGuide system with an automated fiber placement, or AFP, machine manufactured by ElectroImpact (Mulkiteo, WA).
“That improved the cycle time for the laser projector by a tremendous amount,” said Blake. “We have customers who save over an hour on each inspection cycle.”
The LaserGuide software is compatible with FiberSIM, TruLaser, Verisurf, metrology data and other CAD and numeric control data software. It works with the Windows XP, 2000, Vista and 7 operating systems.
Blake recently added imaging to Assembly Guidance’s inspection lasers. Those images are stored permanently, can be enhanced for closer scrutiny of a part, and can be viewed simultaneously in the plant or remotely.
Blake explains that the layup operator is the first inspector, but a second inspector designated by the Federal Aviation Administration has to scrutinize the job too. Sending the image to the FAA-designated inspector’s device—whether he’s on the shop floor or in another part of the plant—helps improve quality and save time over having to locate him and wait for him to inspect the job, he said.
The image is also analyzed by computer software.
“When you use automatic inspection by a computer, critical characteristics can’t be missed,” Blake said. “Human factors of fatigue, distraction and boredom are eliminated.”
In addition to aerospace, Assembly Guidance Systems serves high performance customers in wind turbine, marine, Formula 1, and stock automotive markets around the world.
It also makes Multitasking KitGuide, a system to guide unloading and sorting of plies from the cutting table for up to three parts. Operators using Multitasking KitGuide have the option of wearing wireless printers to generate a label with a barcode to attach to each ply as the table is unloaded.
When it Comes to Composites, Lasers are Hot
Guidance isn’t the only task for lasers on the shop floor in the aerospace industry. Automated Dynamics (Niskayuna, NY) incorporates a proprietary laser system with its tape placement head to consolidate a thermoplastic tow in situ, or heat a thermoset tow, as it’s applied to a work piece. An integrated pyrometer measures the composite material’s temperature and adjusts the laser in a real-time, direct feedback loop, explains Rob Langone, company president.
This allows precise, direct control of material temperature as it’s placed, even when placement speed varies.
Automated Dynamics’s laser system eliminates the need for vacuum bags and autoclaves, along with their associated materials and operating costs. This represents over 90% savings in energy costs when compared to hot gas or infrared heating—and orders of magnitude improvement when the autoclave process can be eliminated.
It also offers some benefit over using hot inert gas, like nitrogen, or an infrared lamp for tow consolidation.
With infrared, the operator has no control over the lamp’s output or the composite material’s temperature, leaving him to make an educated guess about the consolidation process.
“With IR heating, what you can control is two steps away from what you want to control,” said Langone, who started at the company in 1988 as a college student. In addition to developing high-performance automated fiber placement equipment like the laser incorporated with an ATP machine, the 30-year-old company specializes in solution-based engineering services and manufactures advanced thermoplastic composite structures.
Using the laser makes the process three to five times faster than using hot gas or infrared, according to company literature.
The downsides to using the laser include cost, safety and incompatibility with composite materials.
Although a laser heating system is significantly more expensive than alternative heating systems the cost of high-energy lasers is dropping rapidly as the technology improves. However, laser heating is able to deliver energy savings and increased throughput that quickly recoups this increased cost when used in serial production, Langone said.
Because the laser light isn’t in the visible spectrum, there is a potential for eye injury. This is mitigated through the use Automated Dynamics proprietary optics and the use of eye protection and safety interlocks.
And, while carbon fibers readily absorb the laser light’s radiation, glass fibers don’t. Technology is available to make use of laser heating for material systems that are transparent to laser radiation and this technology continues to evolve today.
Carbon and glass are, coincidentally, the two most commonly used materials in aerospace composites. The technology can be also extended to metal and ceramic matrices composites, according to company literature.
In 2015, the National Aeronautics and Space Administration gave Automated Dynamics a small-business research grant to develop its laser heating process further to get it ready for production-level manufacturing. The technology has potential for applications in the automotive, electronics, commercial aviation, medical, energy and chemical processing industries, according to Automated Dynamics’ grant proposal to NASA.
When it comes to computer software related to aerospace automated composite layup, the industry has a milestone anniversary to mark.
It’s been 10 years since CGTech (Irvine, CA) developed the first machine-independent simulation and CNC programming software for AFP and automated tape layup, or ATL. Prior to the software, manufacturers were dependent on machine builder-supplied software that only works with their specific machine, forcing manufacturers to implement multiple off-line NC programming products when using multiple brands or vintages of machines, said Bryan Jacobs, marketing communications manager for the company.
CGTech, an NC verification and simulation software company, offers a suite of three machine-independent software programs for composite layup: for simulation, Vericut Composite Simulation (VCS); AFP or ATL programming, Vericut Composite Programming (VCP); and designing/simulation, Vericut Composite Paths for Engineering (VCPe). They are compatible with most surface model and ply geometry formats including NX, Creo, SolidWorks, STEP, ACIS, Catia V5 and FiberSIM.
The designing/simulation software, VCPe, lets a designer virtually test and experiment with various path options and evaluate the effects automated manufacturing has on a composite part’s design intent. By doing so, VCPe eliminates many possible unforeseen manufacturing process problems that could cause a manufacturing engineer to kick back a part design to the design engineer for modifications because it won’t work on the machine to be used to make the part, said Jacobs.
Features associated with post-processing and post-processing NC programs aren’t included with VCPe: however, the user can measure and evaluate the effects of AFP path trajectory, material steering, surface curvature, course convergence and other process constraints he would find on the shop floor.
CGTech’s CNC programming software reads the same CAD geometry and ply boundary information but also outputs the code the machine will use to run. VCPe files containing AFP or ATL tape courses are compatible with standard VCP and can be used as a starting point for off-line NC programming. Its simulation software emulates the complete AFP or ATL machine that’s going to do the automated layup, and validates the CNC program. Added material is measurable and can be inspected for manufacturing requirements.
Thin is in
Another advance in composites for aerospace is spread tow, aka thin ply. While regular tow might be 5/1,000-inch (127 microns) thick and 20 fibers deep, spread tow is 1/1,000-inch (25.4 microns) thick and made of only four or five fibers though the thickness, said the Institute for Advanced Composites Manufacturing Innovation’s Pipes.
“The thinner we make the tow, the stronger they are,” said Pipes. “We don’t know why, but there are several theories.
“If you can figure that out, you can perhaps learn how to make it even stronger.”
Thin ply is also less prone to cracking and delamination. “The tendency to delaminate is inverse to thickness,” he said.
In the time since Radius Engineering (Salt Lake City, UT) developed same qualified resin transfer molding, a majority of the large aircraft manufacturers around the world have conducted their own development programs on the method, said Tom Coughlin, business developer for Radius, a closed mold tooling and injection systems manufacturer (the company also does process development and workstation design).
“We’ve been doing this long enough that some of our customers are doing it on their own,” said Coughlin, referring to the technology that enables near net shape assemblies. “Where we stay in the game is providing the work cells.”
The principle behind SQRTM (pronounced “squirt ’em”) is that it uses the same resin that’s pre-impregnated in the majority of the composite materials aircraft manufacturers have spent a few million dollars to qualify.
“We wanted to be able to use those materials because they’re important to them (the manufacturers who are Radius’ clients),” said Coughlin. The resin injected during the SQRTM process isn’t used to wet the composite material. Instead, it’s used to maintain steady hydrostatic pressure within the mold to prevent voids, much the same as an autoclave.
There are other advantages to SQRTM, including no need for an autoclave.
Also, SQRTM-manufactured pieces don’t have to be machined to net. “Machining is incredibly expensive,” Coughlin said.
The manufacturing process is streamlined, with no need to catalog, inspect and inventory multiple parts that typically make up primary structures (the parts of an aircraft whose failure would seriously compromise safety, such as fuselages and wings).
It allows manufacturers to “cellularize” their manufacturing: in other words, instead of making one part of an assembly, a work team makes the entire assembly. “I’m making the whole thing,” said Coughlin of the cellularized workers’ mindset. “You’d be surprised how important that is.”
Even if an aircraft manufacturer can’t make an entire primary structure using SQRTM, he can significantly cut down on the number of parts. For example, if a manufacturer needs to incorporate de-icers in a wing flap, he can make the part minus one skin (the upper or lower skin). After the de-icers are added, he can attach the skin. Determinate assembly is the result of net shaped composite manufacturing process.
“This allows us to create an entire assembly and it’s the same way every time,” Coughlin said of the SQRTM method.
Abaris’ Dorworth said; “It’s taking the assembly and all of the inspection related to that into the layup room.”
For more information
Abaris Training Resources
Web site: www.abaris.com
Web site: www.assemblyguide.com
Web site: www.automateddynamics.com
Web site: www.cgtech.com
Web site: www.electroimpact.com
Web site: www.fivesgroup.com
Institute for Advanced Composites Manufacturing Innovation
Web site: www.iacmi.org
Web site: www.lucintel.com
Web site: www.radiuseng.com
Society for the Advancement of Material and Process Engineering
Web site: www.sampe.org