“The vehicles will have to be made from composites because they have to be lightweight,” says John Melilli, president of Composite Automation LLC. Since these services are intended to be ubiquitous, there will be a need for thousands of aircraft. “When they talk about building urban aircraft, they’re not talking about building 30 or 40 a month,” says Melilli. “They’re talking about building 500 to 1,000 units a month.”
Improving on Technology
Manufacturers currently produce many aircraft parts with thermoset composites using hand lay-up and autoclave curing. It’s a labor and capital-intensive process.
Much of today’s manufacturing equipment isn’t designed for higher production rates, either. The specific design details of a part, including its geometry and ply stack-ups, can limit the feed and speed of equipment. “For example, depending on local part curvature, cross-sectional area, ply starts and terminations, and other design details, the equipment will have to slow down to complete a task and avoid creating undesired manufacturing defects,” says Larry Ilcewicz, the Federal Aviation Administration’s chief scientific and technical advisor for composites.
What’s needed to meet the increasing demand are processes that enable scalable and variable rates of manufacturing. Melilli says that manufacturers have to find processes that can move production from manual to automated operations, from resin systems that require going into an autoclave to systems that can get parts production out of the autoclave.
Spirit AeroSystems is currently researching new material systems that improve performance, processing and cost. It’s also developing new high-rate deposition processes. “Material deposition rates and cure times are key to improving fabrication costs and throughput,” notes Hein.
Aerospace composites manufacturers are beginning to research and build processes around fast-cure resin systems. Improvements in cure time will ultimately remove the autoclave or oven as a potential production bottle neck.
Composite parts makers are experimenting with a variety of out-of-autoclave (OoA) technologies, including compression molding, resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), and bladder and mandrel curing.
Thermoplastic in-situ consolidation is one OoA technology that’s attracting interest. Modern laser technology has given manufacturers more control over the temperatures required for working with thermoplastics; they can employ a laser to heat up the thermoplastic resin system and create pressure with a roller, so there’s no need for an autoclave cure.
Robotic tape placement is another possibility with in-situ consolidation. GA-ASI, for example, has introduced a tool-less thermoplastic manufacturing process that uses two robots, one to dispense thermoplastic tape and the other to consolidate it. This eliminates the need for massive tools; only perimeter holding and handling fixtures are necessary.