And it’s not as simple as categorizing materials by fiber type. Consider the overlap: The highest performing S-glass rubs up against the standard industrial grades of carbon fiber for tensile strength. Determining if a material is high-performance likely requires closer examination of a few factors, such as the end-use industry, mechanical performance and fiber configuration.
Each market segment has a different concept of high-performance composites: Aerospace may seek different properties than automotive, architecture or other markets. “Some industries are very concerned about a particular mechanical characteristic, like flexural modulus, tensile strength or compressive modulus,” says Carling. “For them, that’s the driving factor that qualifies a material as high-performance, but it might not be for another industry.”
That’s why it’s critical to consider mechanical performance. “You can accomplish something with a high-performance composite that you cannot accomplish with traditional materials, whether that’s strength or modulus or weight,” says Gert Frederiks, president and CEO of Teijin Aramid. Suppliers offer a variety of reinforcements designed to meet certain characteristics, such as intermediate modulus fibers, high-tenacity fibers, ultra modulus fibers and more. But the terms are used a bit loosely, says Carling.
“Everybody has their own nomenclature for what constitutes aerospace grade,” he says. “I try not to get too settled on the name: I look at the actual mechanical performance of the fiber.” Carling defines high-performance as a raw fiber with a tensile strength greater than 5,000 megapascals (MPa) and tensile modulus above 250 gigapascals (GPa).
IDI Composites International, headquartered in Noblesville, Ind., formulates thermoset molding compounds, including sheet molding compounds (SMC) and bulk molding compounds (BMC). It has a new line of Structural Thermoset Compounds™, manufactured in both sheet and bulk formats, for high-performance applications. The molding compounds use specialized resins and higher levels of reinforcement to provide greater strength, lower coefficients of thermal expansion and better corrosion resistance.
Larry Landis, director of technology and quality for IDI, says his company considers a material high-performance if it can be used in structural applications. “In the SMC field, that’s materials with more than 40 percent fiberglass,” he says. BMC isn’t often looked at for structural applications. While it has some very good structural properties, you can’t typically load the compound with high levels of fiberglass or carbon fiber. But IDI has structural BMCs.