Date of Award:

5-14-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Advisor/Chair:

Thomas H. Fronk

Abstract

Bio-composites are increasing in demand due to governmental incentives across the globe for both environmental and human health reasons. The ideal bio-composite is renewable, recyclable, available, and non-toxic. To properly engineer bio-composite products, the physical properties of the fiber as well as fiber/matrix interactions must be known. The problem lies in the fact that many suitable natural fibers are not currently available in a material form that may be easily worked with. This research investigates methods to process raw kenaf (hibiscus cannabinus) on a scale that allows researchers to make more consistent samples for testing. Though kenaf is highlighted, these processing methods may be applied to any natural fiber. The raw fibers are processed into kenaf chopped strand mats (KCSM) by adapting basic paper-making techniques. KCSM exhibit paper-like qualities and mechanical properties and provide a material of uniform thickness for use in composite parts. Also presented are a basic understanding of natural fiber constituents and effects of mechanical and co-mechanical treatments on those constituents. To test KCSM, samples are made for the ASTM D3039 tensile testing and for testing in a dynamic material analyzer (DMA). Both mechanically and chemo-mechanically processed samples are made for the purpose of comparison. Also, I-beam bridges are built with KCSM to demonstrate how KCSM may be used to create a structure. This is spurred on by the annual SAMPE bridge competition that includes special categories for natural fiber beams. The lay-up procedure is shown in detail to provide a framework that future competitors may use to build quality I-beams for this competition.

The properties obtained by using the KCSM are competitive with other reported properties for kenaf-based composites. A kenaf I-beam demonstrates a strength-to-weight ratio that is 65% of a berglass I-beam built to the same dimensions. Trade-os of using KCSM are the random 2d-fiber orientation and brittle failure, which are not usually desirable in composite components. The chemically treated samples indicate a higher degree of crystallinity but demonstrate inferior mechanical properties when compared to the untreated samples.

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