Nonlinear tensile behaviour of elementary hemp fibres: a numerical investigation of the relationships between 3D geometry and tensile behaviour

Abstract

Nonlinear tensile behaviour of elementary hemp fibres: a numerical investigation of the relationships between 3D geometry and tensile behaviour.Abstract Experimental observations shown that most of plant fibres are characterised by an intricate structure, morphology and organisation. This complex geometrical characteristics may affect the mechanical behaviour of this kind of natural fibres and contribute to the high variability of their mechanical properties. So, this study proposes a numerical investigation on the relationship between the cross-section shape of primary hemp bast fibres and their tensile behaviour. A 3D viscoelastic model based on finite element method is used for this study. Real and elliptical simplified cross-section shapes are considered. Results of the tensile test simulations clearly show the strong influence of the degree of ellipticity on the tensile response of the fibre, and more exactly on the shape of the non-linearity of the response. Results also show that this morphologic effect is strongly related and coupled to structural parameters and physical mechanisms, such as the cellulose microfibrils angle and the viscoelastic behaviour of the material of the fibre wall. Geometric issues could then contribute to explain the different types of tensile behaviour experimentally observed and deserve to be taken into account in plant fibre models.

A viscoelastoplastic stiffening model for plant fibre unidirectional reinforced composite behaviour under monotonic and cyclic tensile loading

“…The reorientation of microfibrils has been demonstrated experimentally on elementary fibre and bundles of fibres under tensile testing [34] and has been correlated to numerical results using a 3D finite element model [35]. The question of this reorientation when bast fibres are used as a reinforcement in the composite is thus highly logical.…”

Beating of hemp bast fibres: an examination of a hydro-mechanical treatment on chemical, structural, and nanomechanical property evolutions

“…At low relative humidity (RH), up to approximatively 10 %, the water molecules were expected to bind to the surface of the sample in a monolayer by van der Waals forces. This involves the hydroxyl groups of hemicelluloses and amorphous cellulose as well as the carboxylic functions of pectin (Célino et al 2014), all present in hemp fibre (Placet et al 2017). Notice that for all samples, the curves where the moisture content was below 10 %RH could be superimposed.…”

“…A small peak approximately 3 µm which intensity increased with the treatment constituted the fibres microporosity could correspond to the lumens. They were defined as hollow and elongated cavities with transversal diameter between 0.5-10 μm (Del Masto et al 2017;Placet et al 2014). This observation obtained with the MIP also matches well with the lumen description visualized by X-ray nanotomography (Beaugrand et al 2017).…”

Quasi-Static and Low-Velocity Impact Behavior of Intraply Hybrid Flax/Basalt Composites

“…Many authors have pointed out this behavior [33,34] that seems to represent a peculiarity of natural fibers, as it has been reported to occur not only in flax [35,36] but also in wood [37] and hemp [38]. Recent studies tried to provide explanations for this behavior, and several mechanisms have been proposed, including cellulose microfibrils reorientation, shear strain-induced crystallization of the amorphous paracrystalline components and degree of ellipticity of the fiber's cross-section [38,39]. Indeed, this effect is significantly reduced in epoxy-based laminates when tested with basalt fibers in the longitudinal direction.…”