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In this last decade, numerous works have been published on the use of metal organic frameworks (MOFs) for applications in adsorption field to remove contaminants from aqueous solutions. However, little is known about MOFs as adsorbents for the removal of fluoride ions from real effluents. In this work, a highly porous MOF, UiO-66-NH2, was used for the final treatment of complex discharge waters containing fluoride ions from a surface treatment plant. Batch experiments showed that MOF exhibited high adsorption capacities towards fluoride ions, leading to concentrations under current regulation values. 70–80 % of the fluoride was removed in 60 min using 100 mg of MOF in 50 mL of effluent without changing the industrial initial pH. At the same time, the treatment also completely eliminated traces of aluminium in the discharge water. All the results showed that adsorption onto a non-conventional material such as UiO-66-NH2 can be an interesting tertiary treatment step to remove more pollutant streams from multi-contaminated industrial discharge waters.

The tonewoods used in musical instruments are finely selected and are subject to current and upcoming availability issues. Wood grading assesses the quality of the tonewood and depends on both subjective and objective criteria. Traditionally, grading criteria based on mechanical properties consider mainly the longitudinal direction. This paper investigates the elastic and damping properties of spruce wood used in the making of acoustical guitars and violins. In this context, the mechanical grading properties will be studied in multiple directions. A non-destructive vibrational characterisation method is used to simultaneously identify at least six mechanical properties of wood and leads to the determination of the elastic and damping parameters of wood along the different material directions. The main objective is to quantify the variability of the mechanical properties in different material directions as a function of the grading attributed by the wood seller. The results show that material anisotropy decreases as the grade decreases. This is attributed to strong increase of the specific elastic modulus in the radial direction and the specific shear modulus in longitudinal and radial plane. Moreover, grading seems to be assigned as a function of specific elasticity and loss factor in the longitudinal direction, which is tied in with the preferences of instrument makers. Following the assumption that high specific modulus is desirable, the classification based on instrument makers choices can be improved for new grading criteria that consider directions than longitudinal. Moreover, the substitution of wood species and the proposal of new materials exhibiting equivalent elastic and damping properties can be proposed.

International audience; The literature focusing on the transverse mechanical properties of single fibers is very sparse compared to those related to longitudinal properties. An original characterization method is proposed herein, relying on a micro mechatronics device to implement a transverse compression test which is monitored using 2D full-field measurements. This is shown to allow for the identification of the transverse elastic properties of a single fiber. The method is used, at first, on a bio-based polymer monofilament (PA11) which is assumed to have regular and controlled dimensions and geometry. The transverse elastic modulus is identified to be equal to approximately 1500 MPa and the longitudinal modulus 2150 MPa. The proposed method is then used to investigate the transverse compressive behavior of contrasted natural fibers, such as beard hair (protein-based) and sisal fibers (polysaccharides-based) which have more complex shape and/or internal structure. This paper gives for the first time the compressive force displacement curves as well as the monitoring of the shape of the cross-section during the loading.

The development of sustainable sandwich materials is needed in the transportation sector to address environmental concerns related to the production and operation of vehicles. In addition to biobased composite skins, alternatives to classic synthetic core materials must be found to reduce the ecological footprint of whole sandwich-structured composites. This study focused on three eco-friendly lightweight core materials: balsa wood, paper honeycomb, and recycled PET foam. The effect of the hygrothermal ageing on their shear creep/recovery behaviour has been here investigated. Two different environmental conditions were tested: 23 °C-50% RH and 70 °C-65% RH. The results indicate that the maximum shear strain, the time-delayed strain and the residual strain increase for the three core materials with the severity of the hygrothermal conditions. This was attributed to the softening of the constitutive polymeric materials of the cell walls at temperatures close to 70 °C. The balsa wood exhibits the best creep resistance under the two environmental conditions. The identification of the viscoelastic properties highlights that the release times and the shear viscous parameter of the balsa wood and the PET foam depended on the stress level and the hygrothermal conditions.

Monitoring integrity of operating structures has become a crucialneed in industrial applications while motivation for moresustainable materials pushes forward the development of naturalfibre composites (NFC). The complexity and variability of theirfailure behaviour and mechanical properties still limit theexploitation of their full potential. Acoustic Emission (AE) hasshown promising results to predict remaining service life ofstructures, allowing identification, localisation and assessment ofdamages in composite materials. Thus, embedment of AE sensors couldbe a reliable solution for real-time Structural Health Monitoring(SHM). This paper aims to quantify

Treatment of wastewater pollution is a critical issue in the context of growing population and industrialization. Actual treatment methods are expensive and not fully effective and rely on fossil fuel-derived chemicals, thus calling for alternative adsorption methods on natural materials such as hemp. Industrial hemp (Cannabis sativa Linn) is a high-yielding annual industrial crop harvested for its fiber from the stem and its oil from the seeds. Hemp is a multi-purpose plant with great potential because of its many uses, such as building materials, textiles, paper, food and beverage, automotive, cosmetics, and medicine. Wastewater treatment is another innovative application. Indeed, the past decade has shown an explosion in the study of hemp-based materials for the biosorption of metal ions from effluents, demonstrating that industrial hemp is one of the most promising materials for environmental applications. Hemp products can be used as biosorbents in granular or felt forms or to prepare non-conventional activated carbons, both used in biosorption-oriented processes. In this chapter, after a brief description of biosorption, the use of different types of hemp-based materials that can be used as pollutant biosorbents is described.

International audience; Flax has a long and fascinating history. This plant was domesticated around 8,000 bce1 in the Fertile Crescent area2, first for its seeds and then for its fibres1,3. Although its uses existed long before domestication, residues of flax yarn dated 30,000 years ago have been found in the Caucasus area4. However, Ancient Egypt laid the foundations for the cultivation of flax as a textile fibre crop5. Today flax fibres are used in high-value textiles and in natural actuators6 or reinforcements in composite materials7. Flax is therefore a bridge between ages and civilizations. For several decades, the development of non- or micro-destructive analysis techniques has led to numerous works on the conservation of ancient textiles. Non-destructive methods, such as optical microscopy8 or vibrational techniques9,10, have been largely used to investigate archaeological textiles, principally to evaluate their degradation mechanisms and state of conservation. Vibrational spectroscopy studies can now benefit from synchrotron radiation11 and X-ray diffraction measurement in the archaeometric study of historical textiles12,13. Conservation of mechanical performance and the ultrastructural differences between ancient and modern flax varieties have not been examined thus far. Here we examine the morphological, ultrastructural and mechanical characteristics of a yarn from an Egyptian mortuary linen dating from the early Middle Kingdom (Eleventh Dynasty, ca. 2033–1963 bce) and compare them with a modern flax yarn to assess the quality and durability of ancient flax fibres and relate these to their processing methods. Advanced microscopy techniques, such as nano-tomography, multiphoton excitation microscopy and atomic force microscopy were used. Our findings reveal the cultural know-how of this ancient civilization in producing high-fineness fibres, as well as the exceptional durability of flax, which is sometimes questioned, demonstrating their potential as reinforcements in high-technology composites.

Lignocellulosic fibers extracted from plants are considered an interesting raw material for environmentally friendly products with multiple applications. This work investigated the feasibility of using hemp- and flax-based materials in the form of felts as biosorbents for the removal of metals present in aqueous solutions. Biosorption of Al, Cd, Co, Cu, Mn, Ni and Zn from a single solution by the two lignocellulosic-based felts was examined using a batch mode. The parameters studied were initial metal concentration, adsorbent dosage, contact time, and pH. In controlled conditions, the results showed that: (i) the flax-based felt had higher biosorption capacities with respect to the metals studied than the hemp-based felt, (ii) the highest removal efficiency was always obtained for Cu ions, and the following order of Cu &gt, Cd &gt, Zn &gt, Ni &gt, Co &gt, Al &gt, Mn was found for both examined biosorbents, (iii) the process was rapid and 10 min were sufficient to attain the equilibrium, (iv) the efficiency improved with the increase of the adsorbent dosage, and (v) the biosorption capacities were independent of pH between 4 and 6. Based on the obtained results, it can be considered that plant-based felts are new, efficient materials for metal removal.

International audience; Retting of fibrous plants such as flax is an essential step in the extraction of fibre bundles and their transformation into textiles and reinforcement fabrics for use in garments and composites. Dew-retting is traditionally performed from Northwest France to the Netherlands, as the climate is highly favourable for this process. Hemp is a plant that can be grown almost all over Europe with a low environmental impact. A retting step is also required to facilitate the separation of the hemp fibres before their transformation into textiles for garments or for 1D to 3D reinforcement composites, which requires thoroughly separated fibres. Dew-retting is currently used in flax production zones. The present work demonstrates that dew retting can be conducted under different climates on different soils, from dry Mediterranean environments up to the cooler regions of eastern France. If the ternary combination of moisture, temperature and solar radiation is appropriate, field retting (dew-retting) can be as short as about three weeks. In less favourable conditions, such as in dryer areas or when retting is performed late in the season after seed maturity (cooler temperatures), it lasts longer, but it can reach suitable levels. When conducted with care and with proper monitoring of the retting level, the dew-retting process does impact neither the tensile properties of elementary hemp fibres (by degrading crystalline cellulose I) nor the tensile properties of unidirectional and injected composite materials. Consequently, if extracted with a suitable process such as scutching and hackling, fibres suitable for load-bearing composites can be produced from dew-retted hemp stems produced in a wide range of climates and locations, therefore not limited to the conventional “dew retting zone” of flax production areas.

The use of recycled and renewable components in structural applications supports the development of sustainable lightweight structures. Disposed bottle caps can be used to generate eco-friendly honeycomb cores, especially when combined with other eco-friendly components. A natural fibre-based laminate represents an alternative to synthetic fibres, matrices, and metals in skins for sandwich panels. This study evaluates the use of flax fibre laminates as sustainable skins for sandwich panels made from upcycled bottle caps core. Metallic skin cases are also tested as a reference. The influence of the amount of adhesive used to produce the panels is also investigated in a 22 full factorial design, together with an independent test carried out on samples made from natural fibres. The characterisation against flexural and low-velocity dynamic loads indicates that the flax fibre skin leads to specific core shear and flexural moduli up to 19% higher than in aluminium-based panels. Unidirectional flax fibres, however, reduce the energy absorption during impact. Flexural properties show that the most efficient design involves the least adhesive amount. Finite element models also show a good fit to the experimental results and indicate a 166% increase of energy absorption with the presence of multidirectional fibre laminates.

International audience; It is generally alleged that the design choices of acoustic guitar bracing patterns lead to a specific sound of the instrument. However, in the presence of strong uncertainties due to variability of material properties and climatic conditions, the robustness of the soundboard dynamics has yet to be investigated. In this study, three types of bracing patterns are studied using physics-based models and stochastic analyses are performed to account for material and climatic uncertainties. It is shown that the choice of a brace design leads, at least in the low frequency domain, to a dynamic behaviour that is not stackable with another design, even in the presence of strong aleatory uncertainties. This assessment supports the conjecture that guitar brace design choices have a greater impact than material variability where guitar soundboard dynamics are concerned. More generally, these results illustrate the usefulness of detailed physics-based models in the understanding, design and making of guitars.

International audience; This paper reviews the damping characteristics of

International audience; Shifting from petrochemical feedstocks to renewable resources can address some of the environmental issues associated with petrochemical extraction and make plastics production sustainable. Therefore, there is a growing interest in selective methods for transforming abundant renewable feedstocks into monomers suitable for polymer production. Reported herein are one-pot catalytic systems, that are active

Despite the increased use of hemp fiber, negligible attention has been given to upgrade the hemp hurd, which constitutes up to 70 wt % of the hemp stalk and is currently considered a low-value byproduct. In this work, valorization of hemp hurd was performed by reductive catalytic fractionation (RCF) in the presence of a metal catalyst. We found an unexpectedly high yield of monophenolic compounds (38.3 wt %) corresponding to above 95% of the theoretical maximum yield. The high yield is explained by both a thin cell wall and high S-lignin content. In addition, organosolv pulping was performed to generate a pulp that was bleached to produce dissolving-grade pulp suitable for textile fiber production (viscosity, 898 mL/g; ISO-brightness, 90.2%) and nanocellulose. Thus, we have demonstrated a novel value chain from a low-value side stream of hemp fiber manufacture that has the potential to increase textile fiber production with 100% yield and also give bio-oil for green chemicals., Hemp hurd, a byproduct from hemp fiber production, was successfully valorized by reductive catalytic fractionation to give high yields of monophenolic compounds and a pulp suitable for textiles or nanocellulose.

International audience; Increasing the production of high-performance natural fibres that minimise their impact on the environment is a challenge that flax (Linum usitatissinum L.) cannot address alone. In flax traditional production territories, hemp (Cannabis sativa L.) can be a complementary source of high added value fibres if their yield of long line fibres can be maximised to levels equivalent to the one of flax. The objective of the present work was to establish process parameters maximising the long line fibre yield using flax dedicated scutching and hackling devices. A lab-scale scutching/hackling device was used to establish sets of process parameters which best improve the long fibre scutching yield and as a consequence minimise the production of tow fibres. Decreases in straw processing transfer and beating speeds during scutching were necessary so that to be less aggressive on the straw and fibres. Very high long fibre yields were obtained after scutching and hackling at the laboratory scale (18 % of the hemp straw mass). These very high results, combined to high straw yield production in the field indicate that hemp can be a very productive source of high-performance fibres as these ones showed tensile properties completely suitable for a textile use as well as for load bearing composite materials. If the potential of high production yields and high mechanical and morphological properties was demonstrated at the lab-scale, this one should be improved at the industrial scale. Suggestions to reach this goal are provided to prevent too high transformation of long fibres into tows and to keep the mechanical potential maximum. When using optimised parameters and a lab-scale scutching/hackling device, it was demonstrated that hemp has the potential for providing equivalent amounts of long fibres per hectare than flax with tensile properties about 20 % lower than the ones of flax.

International audience; Prompted by environmental legislation and citizens’ awareness induced by global warming ef-fects, the market for plant-fibre reinforced composites has been growing steadily for the past 10–20 years, as observed by the substantial increase in academic and industrial research de-velopments. However, the transition to larger production still requires several uncertainties to be overcome. Among these uncertainties, defects in plant fibres are known to decrease the me-chanical properties at the composite scale. It is therefore of interest to better understand the defects nature, origin and consequences at the fibre scale to monitor the use of plant fibres as reinforcement. In recent decades, finite element modelling has emerged in various scientific fields as an interesting tool that complements experimental characterization. Finite element modelling is even more critical for small and intricate elements such as plant fibres where standard me-chanical tests require substantial adjustments and investments due to their complex ultrastructure compared to synthetic materials. The main objective of this review is to provide a novel overview of defects found in plant fibres and their influence on the mechanical properties of plant fibres based on experimental and modelling work. Through a top-down and multi-scale approach, we first describe the flax fibre ultrastructure with a focus on defects. Then, advanced testing methods and emerging numerical approaches that capture the complex mechanical behaviour of plants, especially flax fibres, are addressed.

This work describes the physical and mechanical characterization of unidirectional [0]12 and crossply [(0/90)3/ 0 ‾ ]S flax fibre reinforced composites fabricated in autoclave using a prepreg flax tape impregnated with fire retardant epoxy polymer. Tensile, bending and impact properties are evaluated along the longitudinal and transverse fibre directions. The tensile-tensile fatigue behaviour is characterised along the fibre direction. Physical and specific properties are also assessed to identify the potential characteristics of these bio-based composites for lightweight and secondary loadbearing applications. The robust manufacturing process described in this work, coupled with precision laser cutting, makes this type of composite a promising sustainable material for aircraft, transport and lightweight construction designs.

International audience; Substitution of fossil energy sources for bio-based ones will require development of efficient processes that can convert inedible and preferably low-value fractions that currently are not used into high-value products. It is desirable that such processes are developed so that both current logistics and infrastructure can be used. Bark, which is the outer layer of woody biomass, is currently burnt in a low-value process or left in the forests to decay and is therefore considered waste. In this work, birch (Betula pendula) bark was converted to hydrocarbons suitable for use in both road and aviation fuels in two efficient steps. Development of an efficient, recyclable, salt- and metal-free solvent-based system to solubilize birch bark under benign reaction conditions was a key outcome. The obtained gum was composed of organosolv lignin and suberin oligomers and was fully characterized. This gum had unique properties and could be directly processed in a conventional hydroprocessing unit set-up to afford hydrocarbons in the road and aviation fuel ranges. Life cycle assessment was applied to evaluate different scenarios for implementing this technology. When using bark generated as a forestry by-product and current infrastructure in a pulp mill, the process had a favorable low carbon dioxide footprint for biofuel generation.

International audience; Recent developments in the field of bio-based composite materials are mainly focused on the use of unidirectional reinforcements. The production of woven fabrics and required yarns or rovings isstill complex for composite applications due to the finite length of plant fibers and to the high number of process parameters which can be tuned. This study focused on the influence of weave pattern and process parameters on the resulting material properties at different scales. Results from mechanical characterizations and X-ray nanotomography show that very competitive tensile properties can be obtained for woven hemp fabric composites made from low-twisted rovings, in particular when compared to the front-runner flax cross-ply laminate.

International audience; The ability of Capacitive Micromachined Ultrasonic Transducer (CMUTs) todesign broadband sensors for Structural Health Monitoring (SHM) is studiedthrough both multi-frequency and bandwidth aspects. Elementary cells arecomposed of circular membranes fabricated using the standard MUMPS Process. The multi-frequency aspect, which involves different individual membranes from 50 µm to 250 µm radius, is theoretically addressed through anumerical modeling. The targeted frequency range, consistent with the SHMapplication, is then between 80 kHz and 2 MHz. Geometrical features induced by the manufacturing process greatly affect the dynamic properties ofthe membranes and this is experimentally validated. The bandwidth aspectis also addressed on an array of identical 100 µm radius membranes thusinvolving their intrinsic capabilities. Harmonic excitation with targeted frequencies 300 kHz, 530 kHz and 800 kHz, below and beyond the resonancefrequency of the membranes, are performed. The influence of the bias voltage VDC on the signal-to-noise ratio is studied according to the excitationfrequency. As a result, a signal-to-noise of 20 dB is achieved around the resonance frequency. Finally, the circular membranes array is tested for acousticemission sensing through a pencil lead break test. In spite of a low signal-tonoise ratio, acoustic events are clearly detected. The multi-frequency aspectand the large bandwidth capability of the CMUTs are hence demonstratedand highlight the adaptability of the sensor to its environment.

International audience; This work explores the use of supercritical carbon dioxide (sc-CO2) conditions as an innovative and environmentally friendly treatment of plant fibres to optimize their performance for integration into composite materials. This study evaluates, in particular, the influence of this treatment on the mechanical, thermal, hygroscopic properties and biochemical features of industrial hemp bast fibres. Two distinct settings were tested by tuning time, temperature and pressure parameters to assess the influence of the severity of the treatment on the fibre quality. Results show that sc-CO2 treatment induces an increase in the fibre fineness and a decrease in their moisture sensitivity while maintaining their initial resistance to temperature. These changes are consistent with the measured decrease in the relative content of hemicelluloses. A significant decrease in the tensile rigidity and strength is also observed as a function of the severity of sc-CO2 treatment, counterbalancing a little bit the benefits retained on the other properties.