Bio-Industrial Materials Institute: Characterization of Natural Fiber Material Property Variability

Abstract

To become a more competitive alternative to synthetic fibers, the variability of natural bast fiber material properties must be understood. Standardizing the relationship between these fibers and their associated material properties will broaden the range of applications to include more technical industries. Initial tensile testing showed variability within all bast fibers, and flax was used to investigate methods to reduce variation. Single strands of fibers were selected, tabbed, and then placed in a fiber dimensional analysis system to record their diametral geometry. Observations for various physical defects were catalogued before tensile testing the fiber. Material property data were filtered according to defects in the fiber’s observed physical characteristics. High variation of fiber mechanical properties was reduced by accounting for various physical defects including kinks, geometric inconsistencies, fraying, and transient data due grip failure or unexplained loss of load carrying capability. While fiber color was not found to significantly affect the strength or modulus of the fiber, darker hemp fibers were found to have reduced standard deviation when compared lighter or spotted fibers. Based on these results, microscopy was performed to assess fiber constituents. Comparing modulus with lignin content for bleached flax fibers, a slight increase in modulus was noted as the percent area of lignin increased. Excepting this weak trend, no other trends could be established between the lignin content and either tensile strength or modulus in any of the other natural fibers. These results conflicted with literature studying agave plant fibers, wherein cellulose-to-lignin ratios were associated with higher tensile strength values. As such, future work is anticipated to better understand the fiber constituents toward characterization as well as investigate effects of decortication to maintain structural quality and length continuity of bast fibers.