A long-standing roadblock to greater market share for composites is destined for demolition.
Wider adoption of composite materials in the built environment has long been the goal of the composite industry. However, a dearth of published performance criteria for composite structures has been a major roadblock to increasing market share, says Tom Dobbins, chief staff executive for the American Composites Manufacturers Association (ACMA).
“The completion of a three-year program to publish pre-standards for load and resistance factor design (LRFD) for pultruded fiber-reinforced polymer (FRP) products marks the beginning of a new era in the composites industry,” he says. “When the adoption process of the pre-standards is complete, composites will achieve a much higher level of acceptance.”
If pultruded products are going to be competitive in the marketplace, engineers and designers need LRFD standards, states John Busel, director of ACMA’s Composites Growth Initiative (CGI). The initiative aims to expand the use of composites in a wide range of markets.
“If I’m a structural engineer, and I have a project to build, like a cooling tower in a nuclear power plant,” says Busel, ” and I can choose to make it out of non-corrosive materials instead of wood or steel, what tells me how to design with composites? Until now, I had to refer to individual pultruder guidelines based on older design methodology called allowable stress design.”
Load and Resistance Factor Design (LRFD) refers to a design methodology that makes use of load and resistance factors based on the known variability of applied loads and materials. Structural engineers use LRFD because it is widely becoming a preferred method for design, replacing other methods such as Allowable Stress Design. LRFD is also referred to as reliability-based design—the direction all civil engineering design codes are moving.
Why do we need it?
Composites are now generally recognized as excellent materials in many construction and civil infrastructure applications. Attractive qualities include strength and stiffness, durability, high corrosion resistance and light weight.