I-Corps: Recycled plastic lumber building material replacement for structural lumber

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The broader impact/commercial potential of this I-Corps project is the development of a recycled plastic building material intended as a drop-in replacement for structural lumber. This proposed material is similar in cost to lumber and may provide equivalent installation methods, may reduce weight, and may prevent damage due to rot and insects. The proposed initial application is the US agricultural fence post market: 206 million linear feet of fencing or 15 million fence posts annually. Using current lumber prices, this market is estimated to have a current value of $98 million. The softwood sawn dimensional lumber, the targeted industry, has an approximate market value of $39 billion in the United States. Based on initial customer interviews, wood fence posts typically last 10-20 years. The polymers utilized in the proposed material have a useful life of 30-50 years, significantly reducing future costs for end users. Additionally, the reduction in wood usage could reduce the 10 million acres of forest harvested for fence posts each year in the United States. The goal is to develop a material that directly replaces lumber while utilizing low-cost recycled materials and providing a similar or reduced price compared to lumber.This I-Corps project is based on the development of a composite material that matches the driving force and withdrawal force of nails and other fasteners used in wood. The proposed material utilizes an over jacketing extrusion technique to increase the gross mechanical strength of the section as well as a hollow composite composed of the proposed materials. The innovation requires an increase in the coefficient of friction while reducing the compressive strength to allow for nails to be driven by hand. Over jacketing extrusion must be reconfigured to allow for coextrusion of the bulk composite material with macro-reinforcement, which is similar to the reinforcement method used in reinforced concrete. These requirements must be maintained while allowing for a hollow section to reduce material costs. The project seeks an improved understanding of the influence of additives or fillers based on polymer-based composites. Fillers provide advantages including reduced costs, increased stiffness, and increased compressive strength, and their usage has increased in the polymer industry. Futrue activities will focus on the introduction of fillers for increased friction in mechanically fastened connections.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.