The events of the past couple years have prompted fabricators to think differently about material choices such as aluminum. In early 2022, pent-up demand for the alloy was projected to deplete global stockpiles by as early as 2024. The industry has seen historic price hikes followed by recent reductions. Like other raw materials, aluminum continues to teeter between the constraints of supply chain disruptions and a deteriorating economy. Despite demand, the energy crunch, inflation, and geopolitical influences are hobbling production—factors that could move aluminum from a deficit to surplus.
As part of the U.S. Federal Sustainability Plan, companies are being tasked to achieve 100 percent carbon-free electricity by 2030. Aluminum appeals to manufacturers because it offers high strength, recyclability, and corrosion resistance combined with thermal and electrical conductivity. But energy costs for the metal account for more than one-third of production costs. In the current climate, manufacturers are not only looking at material substitutions, but in some cases advanced material technologies such as fiber-reinforced-polymer (FRP) composites. The drive toward more sustainable structures with a small carbon footprint has already created a growing niche for products that combine steel and FRP.
FRP offers an attractive alternative to metals such as aluminum. The composite is high-strength, lightweight, and corrosion resistant. It is also 99 percent sourced in the U.S.
But manufacturers and fabricators need to consider the application and performance requirements. An understanding of some of FRP’s traits also helps a design engineer determine if the material is an option. FRP’s longitudinal tensile strength rivals or exceeds a number of aluminum grades. FRP’s density is comparable to that of aluminum, and, in some cases, epoxy carbon pultrusion is lighter than aluminum.
Composites can also absorb impact energy with half the modulus of elasticity than that of aluminum. FRP will not permanently deform under a working load. Metals typically deform more easily, and permanently, under the same conditions.
FRP is inherently corrosion resistant, warding off chemicals, salt, and water. For infrastructure applications, design flexibility allows these products to be tailored for flame retardants, temperature resistance, UV protection, and higher corrosion resistance. These additives are easier and simpler to add to FRP versus other materials.
To meet stiffness requirements, a thicker glass fiber can be used and still retain lighter component weight. FRP has low thermal conductivity and zero electrical conduction. As a result, the composite material is able to retain reliability and performance properties in varying conditions.
Fiber architecture can be customized to manipulate mechanical and performance characteristics in different directions. Composites are a non-homogeneous material with properties that vary as a function in the body of a product.
The ladder industry, for example, has migrated from aluminum to fiberglass. In addition to rigidity and sturdiness, FRP ladders are non-conductive, thus safer when working around hot/live wires.
The ability to prefabricate FRP products also has the potential to reduce overall costs and make installation quicker and easier.The construction, automotive, and aerospace industries continue to look at composites as a robust alternative. Composites are also being adopted for waterfront infrastructure applications such as piers, pilings, and retaining walls.
Composites, aluminum, and other metals all are useful. To make the right choice, design engineers must assess ease of manufacture, environmental conditions, cost, and chemical and mechanical properties.
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