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Title: Sources of Flax Submitted for Composite and Fiber Characterization

Author
item ALCOCK, MERCEDES - Composites Innovation Center
item Foulk, Jonn
item ULVEN, CHAD - North Dakota State University

Submitted to: Composite Innovation Center(CIC) Technical Report
Publication Type: Other
Publication Acceptance Date: 10/4/2009
Publication Date: 1/7/2010
Citation: Alcock, M., Foulk, J.A., Ulven, C. 2010. Sources of Flax Submitted for Composite and Fiber Characterization. Composite Innovation Center(CIC) Technical Report. Report No. 08-020-02 R01.25.

Interpretive Summary: Attempts were made to quantify attributes of eighteen fibre samples that were selected based on processing variables that may influence fibre properties. In total, 22 different test groupings were performed: adsorption, colour, conductivity, cuticle content, density, fibre length, fibre strength, image analysis, fineness, glucose content, hollowness, hydrophobicity, metals content, microorganisms, moisture content, openness, organoleptic testing, pectin content, ph, polarity static decay, shive content, and wax content. Each of the test groups was hypothesized to measure variables that directly, indirectly or acted as an indicator for a property that did have a direct or indirect influence on composite performance. Indicator values, while not direct measurements of the properties, could prove to be a more cost effective method than direct testing once the relationship between indicator and fibre quality was determined. Measured flax physical and chemical properties could potentially impact binding and thus the stress transfer between the matrix and fiber.

Technical Abstract: Biofiber variability due to different cultivation techniques, retting conditions, and processing techniques is one of the main concerns for the composite industry to incorporate biofibers into production parts. Presently, the impact of most fibre characteristics on thermoset composite performance and the range of variability within different fibre sample sets are unavailable. Understanding the relationship between fibre characteristics and composite performance is an important aspect in creating test standards, developing treatments to improve composite performance, achieving consistent composite products, contrasting different fibre processing techniques, and establishing value for quality in the supply chain. In order to evaluate fibres holistically, a preliminary investigation of fiber characteristics and their relationship to composite performance was developed. The approach was to evaluate a wide variety of fibre quality variables and when available, use multiple test methods to determine if trends could be established between these variables and various test methods, fibre sources, and most importantly, composite performance. Identified trends could then be used to determine the direction of subsequent research to substantiate relationships. Flax (linseed) and hemp are bast fibre plants that are grown commercially in Canada for seed. Both plants contain fibres that have the potential to replace E-glass in composite parts. Based on availability, commercial supply, international support, and to limit the work scope of the project, flax was chosen for the study. Eighteen flax samples were selected based on the perception that the samples would contain a representation of the large spectrum of influencing variables on fibre characteristics including mechanical processing methods, degree of ret, method of ret, variety (fiber or linseed), and year of harvest. Attempts were made to quantify attributes of the eighteen fibre samples that were selected based on processing variables that may influence fibre properties. In total, 22 different test groupings were performed: adsorption, colour, conductivity, cuticle content, density, fibre length, fibre strength, image analysis, fineness, glucose content, hollowness, hydrophobicity, metals content, microorganisms, moisture content, openness, organoleptic testing, pectin content, ph, polarity static decay, shive content, and wax content. Each of the test groups was hypothesized to measure variables that directly, indirectly or acted as an indicator for a property that did have a direct or indirect influence on composite performance. Indicator values, while not direct measurements of the properties, could prove to be a more cost effective method than direct testing once the relationship between indicator and fibre quality was determined. To correlate the fibre properties to composite performance, a series of composite tests were undertaken to provide comparative analysis. All composite specimens were fabricated using Hydropel R037-YDF-40, a low viscosity, thermosetting vinyl ester resin, suitable for resin infusion processing. This resin was chosen due to its suitability for ground transportation parts and good adherence to the fibres as compared to other resins of similar purpose. A fibre pullout test and an interlaminar shear strength test were chosen to evaluate interfacial bond strength. Impact performance (ASTM D4812) was selected to determine if certain fibre properties correlated to impact performance more than interfacial bond strength. Fibre diameter and the percentage shive in biocomposite were suspected of being strong influences based on previous research and composite theory. Fiber diameter and shive content were investigated via tensile testing (ASTM 3039) in absence of other masking parameters to determine their influence on composite performance. This report pro