Customers want to try thermoplastic composites for a variety of reasons, according to Uzman. In structural applications, end users want the interlaminar shear and tension strength of thermoplastic composites, which makes them a good choice for parts that try to flex under load, such as I-beams, spars, fuselage frames and some wing skins. Other customers are more interested in thermoplastics’ damage-resistance properties. They want to protect aircraft surfaces from damage when a tool is dropped, when items get shoved into cargo bays or when a passenger in high heels walks on the laminate.
“Automotive is interested in black sheet metal – they want composites that behave like steel when they form them. So we do a lot of work in the simulation of 3D shapes in the forming process,” Uzman adds. These customers are experimenting with a variety of thermoplastic manufacturing techniques. “In the automotive world, the material system has not been locked in place yet. Some favor the infusion process with epoxies, some favor thermoplastics and lamination forming, and there is some effort in the infusion of thermoplastics with low viscosity thermoplastic resins.”
Striking the Right Balance
Consulting firm Forward Engineering assists international automotive OEMs and parts manufacturers that are interested in lightweight structures and composite materials. Forward Engineering has worked primarily with thermoset composites in the past, but today its projects are split evenly between thermoset and thermoplastic composites. The company’s clients are looking at the potential of thermoplastic composite in high-volume, low-cycle-time, automated production of structural parts.
“OEM’s have a broad portfolio of materials to choose from, including lightweight metals that they are very familiar and comfortable with,” says Adam Halsband, Forward Engineering’s managing director. “For thermoplastic composites to be attractive, they must strike the right balance of mass, cost and performance.” OEMs consider design, material and manufacturing to determine the feasibility of using any product, and thermoplastic composites manufacturers have some remaining challenges to overcome there.
One is the lack of good data. To properly design structural parts, engineers need to understand thermoplastic composites’ properties so they can input that information into their modeling and simulation programs. (Halsband refers to this data as “material cards.”) Forward Engineering has been working with leading material suppliers to accelerate the development of these material cards.
The availability of thermoplastic composites in the necessary quantities and at a competitive price is another problem. “For manufacturing, there needs to be a capable supply base,” Halsband says. Advances in automated manufacturing processes and in the high-volume production of continuous and discontinuous fiber organosheets should help address both availability and cost concerns.