Simulation of tensile tests of hemp fibre using discrete element method

Abstract

Abstract: Tensile strength is an important property of hemp fibre, because it determines the mechanical strength of fibre-based products such as biocomposites.  Commercial discrete element software, Particle Flow Code in Three Dimensions (PFC^3D), was used to develop a numerical model which simulates tensile tests of hemp fibre.  The model can predict the tensile properties (such as strength and elongation) of a hemp fibre. In the model, a virtual hemp fibre was defined as a string of spherical balls, held together by cylindrical bonds implemented in PFC^3D.  To calibrate the model, tensile data was collected for both unretted and retted hemp fibres using a commercial Instron testing system.  The average fibre diameter was 0.34 mm for the unretted fibre and 0.30 mm for the retted fibre.  The average tensile strength measured was 358 MPa for the unretted fibre and 343 MPa for the retted fibre.  The corresponding average elongations for the two types of fibres were 0.88 and   0.80 mm, for an original fibre length of 25 mm.  The bond modulus, the most sensitive microproperty of the model was calibrated.  The calibrated value was 1.02×10¹⁰ Pa for unretted fibre and 1.05×10¹⁰ Pa for retted fibre.  Using the calibrated bond modulus, elongations of fibre were simulated using the model.  The simulation results showed that the elongation increased linearly with the increasing fibre length; whereas the elongation was not affected by the fibre diameter. 

Keywords: hemp, fibre, PFC^3D, tensile, strength, elongation, simulation