Hemp fiber production: development of an automated peeling decorticator to produce optimal fiber for biocomposites

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Schwed, Tim
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Electronic thesis
Mechanical engineering
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Around the world there has been an increased focus on finding more sustainable and environmentally friendly options for a variety of manufacturing industries and practices. The composites industry, for example, is one with significant waste, a large carbon footprint, and poor end-of-life options. There has been a recent trend to reduce this impact by replacing synthetic fibers (e.g., E-glass, Aramid) with natural fibers. Hemp fiber has come forward as a competitive alternative to synthetics due to its high strength-to-weight and modulus-to-weight ratios, and its economic competitiveness when compared to other common natural fibers like cotton. Although hemp fiber has been used for centuries, there are still improvements to be made to the processing of the fiber. The current automated decortication processes – the automated process to separate the hemp fiber from its inner woody core called ‘hurd’ – is typically an aggressive process that can damage fibers and results in a tangled mess. The resulting fiber quality, while efficiently produced, is not of high enough quality to be used for advanced composite applications. This research looks to develop an automated machine that can perform decortication on hemp stalks without damaging fiber, yet allowing it to be custom-cut to length for use in high-performance biocomposite components. A novel and useful splitting and peeling decortication process is demonstrated, and a machine is developed for process automation. Specifically, flattened stalks are fed into a splitting wedge using rubber-coated pinch rollers, the stalks split into two halves, and are broken at the split ends to peel the fiber away from the intact hurd. The fiber halves are pulled sideways using two sets of pinch rollers while the splitting wedge drops downward and the peeled hurd proceeds downwards. Experiments with two machine prototypes show that this machine design and decortication process is a viable option for producing undamaged hemp fiber suitable for high-performance biocomposites, while still maintaining throughput and efficiency levels delivered by automation. While future work is required to transform this machine into a commercial product, the reliability and effectiveness of the machine has been demonstrated.
School of Engineering
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Rensselaer Polytechnic Institute, Troy, NY
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