Swelling of natural fibre bundles under hygro- and hydrothermal conditions: Determination of hydric expansion coefficients by automated laser scanning

Garat, William; Moigne, Nicolas Le; Corn, Stéphane; Beaugrand, Johnny; Bergeret, Anne

doi:10.1016/j.compositesa.2020.105803

Cited by 44 publications

(16 citation statements)

References 27 publications

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“…Water pretreatment generates a water uptake by the fibers, which occurs under two states in natural fibers, depending on the moisture content [ 22 , 27 , 28 ]: (i) Water bound to the different biopolymers constituting the cell walls and middle lamella, involving the formation of hydrogen bonds with hydroxyl groups OH, and (ii) free water that fills voids (micro- and macropores of cell walls and lumens) and is retained by capillary forces. Garat et al [ 29 ] measured moisture content of 62.8 ± 0.7% for hemp fiber bundles in immersion (compared to 60.9 ± 0.7% for flax fiber bundles). Moreover, Pejic et al [ 28 ] showed that lignin removal decreases the moisture sorption and increases the water retention ability of hemp fibers.…”

Section: Resultsmentioning

confidence: 99%

“…On the contrary, Sawpan et al [ 24 ] and Sair et al [ 33 ] observed an increase of tensile properties for hemp fibers after alkali treatments that they attributed to a relaxation and reorganization of the microfibrils along the principal axis of the fiber, resulting in a more rigid structure thanks to the elimination of lignin and hemicellulose components. Besides a reduction of lignin and hemicellulose amounts [ 29 , 30 ], authors report a transformation of cellulose II to cellulose I [ 33 ] and an augmentation of the cellulose crystallinity [ 31 ] after application of an alkaline pretreatment to the fibers.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Alkali and Silane Treatment on Hemp/PLA Composites’ Performance: From Micro to Macro Scale

et al. 2021

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This study investigated the effect of hemp fiber pretreatments (water and sodium hydroxide) combined with silane treatment, first on the fiber properties (microscale) and then on polylactide (PLA) composite properties (macroscale). At the microscale, Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy investigations highlighted structural alterations in the fibers, with the removal of targeted components and rearrangement in the cell wall. These structural changes influenced unitary fiber properties. At the macroscale, both pretreatments increased the composites’ tensile properties, despite their negative impact on fiber performance. Additionally, silane treatment improved composite performance thanks to higher performance of the fibers themselves and improved fiber compatibility with the PLA matrix brought on by the silane couplings. PLA composites reinforced by 30 wt.% alkali and silane treated hemp fibers exhibited the highest tensile strength (62 MPa), flexural strength (113 MPa), and Young’s modulus (7.6 GPa). Overall, the paper demonstrates the applicability of locally grown, frost-retted hemp fibers for the development of bio-based composites with low density (1.13 to 1.23 g cm−3).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Impact of Alkali and Silane Treatment on Hemp/PLA Composites’ Performance: From Micro to Macro Scale

et al. 2021

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“…X-ray tomography conducted on a single wood fibre by Joffre et al [38] showed dimensional changes when increasing the ambient relative humidity from 47% to 80%, but without focusing on the lumen shape. Garat et al [8] determined a decrease of the form factor of flax bundles under increasing relative humidity conditions. In these cases, the fibres might swell in an anisotropic way partly to recover their in-planta rehydrated and more circular state.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, porosities in plant fibres are also the location of free water filling at high moisture content. This water is involved in the hydric expansion coefficients of the fibre, and, in other words, determines its dimensional characteristic [8] and related hygromorph properties [9]. From an engineer or material scientist point of view, porosity is an important characteristic of plant fibres to deal with in order to tailor Fibers 2021, 9, 24 2 of 17 plant fibre composites.…”

Section: Introductionmentioning

confidence: 99%

Novel Insight into the Intricate Shape of Flax Fibre Lumen

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Durand

Melelli

et al. 2021

Fibers

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Plant fibres and especially flax can be distinguished from most synthetic fibres by their intricate shape and intrinsic porosity called lumen, which is usually assumed to be tubular. However, the real shape appears more complex and thus might induce stress concentrations influencing the fibre performance. This study proposes a novel representation of flax fibre lumen and its variations along the fibre, an interpretation of its origin and effect on flax fibre tensile properties. This investigation was conducted at the crossroads of complementary characterization techniques: optical and scanning electron microscopy (SEM), high-resolution X-ray microtomography (µCT) and mechanical tests at the cell-wall and fibre scale by atomic force microscopy (AFM) in Peak-Force Quantitative Nano-Mechanical property mapping (PF-QNM) mode and micromechanical tensile testing. Converging results highlight the difficulty of drawing a single geometric reference for the lumen. AFM and optical microscopy depict central cavities of different sizes and shapes. Porosity contents, varying from 0.4 to 7.2%, are estimated by high-resolution µCT. Furthermore, variations of lumen size are reported along the fibres. This intricate lumen shape might originate from the cell wall thickening and cell death but particular attention should also be paid to the effects of post mortem processes such as drying, retting and mechanical extraction of the fibre as well as sample preparation. Finally, SEM observation following tensile testing demonstrates the combined effect of geometrical inhomogeneities such as defects and intricate lumen porosity to drive the failure of the fibre.

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“…The exposure causes aging, which needs to be studied to evaluate their behavior during their service life. In general, the dimensional stability of the composites and their mechanical performance are strongly influenced by hygro-thermal and hydro-thermal conditions, which are related to relative humidity and immersion conditions, respectively [ 97 ]. The ability of natural fibers to absorb moisture relies on the hydrophilic nature of the fibers itself.…”

Section: Factors Determine the Mechanical Failurementioning

confidence: 99%

A Review on Mechanical Performance of Hybrid Natural Fiber Polymer Composites for Structural Applications

et al. 2021

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In the field of hybrid natural fiber polymer composites, there has been a recent surge in research and innovation for structural applications. To expand the strengths and applications of this category of materials, significant effort was put into improving their mechanical properties. Hybridization is a designed technique for fiber-reinforced composite materials that involves combining two or more fibers of different groups within a single matrix to manipulate the desired properties. They may be made from a mix of natural and synthetic fibers, synthetic and synthetic fibers, or natural fiber and carbonaceous materials. Owing to their diverse properties, hybrid natural fiber composite materials are manufactured from a variety of materials, including rubber, elastomer, metal, ceramics, glasses, and plants, which come in composite, sandwich laminate, lattice, and segmented shapes. Hybrid composites have a wide range of uses, including in aerospace interiors, naval, civil building, industrial, and sporting goods. This study intends to provide a summary of the factors that contribute to natural fiber-reinforced polymer composites’ mechanical and structural failure as well as overview the details and developments that have been achieved with the composites.

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Swelling of natural fibre bundles under hygro- and hydrothermal conditions: Determination of hydric expansion coefficients by automated laser scanning

Cited by 44 publications

References 27 publications

Impact of Alkali and Silane Treatment on Hemp/PLA Composites’ Performance: From Micro to Macro Scale

Impact of Alkali and Silane Treatment on Hemp/PLA Composites’ Performance: From Micro to Macro Scale

Novel Insight into the Intricate Shape of Flax Fibre Lumen

A Review on Mechanical Performance of Hybrid Natural Fiber Polymer Composites for Structural Applications

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