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Characterization of the Shear Properties of Hemp Fiber and Core Using the Discrete Element Method

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 54(6): 2279-2285. (doi: 10.13031/2013.40641) @2011
Authors:   M. A. Sadek, Y. Chen, C. Laguë, H. Landry, Q. Peng, W. Zhong
Keywords:   Cohesion, Direct shear test, Discrete element, Friction, Hemp, Modeling, Stiffness, Stress, Yield

Processing of hemp for fiber involves mechanical separation of the outer fiber layer from the inner core of the hemp stem. Existing processing equipment is often not effective due to lack of information on the mechanical properties of hemp fiber and core. In this study, direct shear tests of hemp fiber and core were performed to measure the yield strength, cohesion, and internal friction of these two materials. The materials were ground into small particles before the tests. A numerical model was developed to simulate the direct shear tests using PFC3D (Particle Flow Code in Three Dimension), a discrete element program. The model consisted of an assembly of spherical particles (2 mm diameter) that represented ground fiber and core particles. The particle assembly was virtually sheared under different normal loads to obtain the shear properties (yield strength, cohesion, and internal friction) of the model particles. The microproperties (particle friction and stiffness) of the model particles were calibrated using the measurements from the direct shear tests. The calibrated values of normal stiffness and shear stiffness were 5e4 N m-1 for the ground fiber and 8e4 N m-1 for the ground core, and the calibrated friction coefficient of the particles was 1.0 for both the ground fiber and core. The shear properties simulated with the model were validated with the measurements, and they agreed well with the measurements in most cases.

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