Biomechanical properties of miscanthus stems

Miscanthus × giganteus is emerging as one of the most promising crops suitable for biomass production, as it requires low inputs and produces high yields. Miscanthus harvesting using forage and hay equipment presents a challenge because of the thickness and hardness of miscanthus stems. Biomechanical properties of the miscanthus stems were investigated for use in designing better harvesting and size reduction equipment. Material testing equipment was used to study cutting force, shearing strength, tensile strength, and bending strength. The cutting force was determined at the first internode, whereas other properties were determined at internodes one through seven. The shear strength of miscanthus stems at the first or second internode was about double that at internodes three through seven. Tensile strength of the cortex in the cross-sectional direction was about 0.4% of tensile strength in the longitudinal direction. Shearing strength of the cortex was 7.0 and 65.0 MPa and tensile strength was 288.1 and 1.1 MPa in the longitudinal and cross-sectional directions, respectively. The modulus of elasticity of miscanthus stems increased from 4,600 to 11,300 MPa as the internode number increased from first to seventh. The maximum cutting force to cut miscanthus stems was 83.0 N mm ^-1 for a flat blade and 54.6 N mm ^-1 for a serrated blade. The specific cutting energy was 87.5 mJ mm ^-2 for the flat blade and 66.1 mJ mm-2 for the serrated blade. Analysis revealed that the serrated blade employed less energy-demanding modes of failure than the flat blade, resulting in lower cutting energy and reduced cutting force. The results of this study may be useful in designing harvesting and size reduction equipment employing optimum failure modes to minimize the energy or to achieve desired quality of cut.