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International audience; In this study coatings of kaolin and talc particles were successfully applied on the surface of polyamide 12 powder intended for laser sintering (LS). Microscopic observations revealed that using carboxymethyl cellulose (CMC) as surface modifier for fillers led to a better coverage of polymer grains with a surface coverage between 6 and 16% as a function of filler type and content. Differential scanning calorimetry measurements showed that the addition of talc and kaolin led to an increase in the crystallization temperature of PA12, but at the expense of processability. Process parameters were optimized in order to manufacture LS samples with the different coated powders. Fire behavior assessed by cone calorimetry showed that the use of CMC resulted in a significant decrease in the peak of heat release rate depending on the filler type and content. This behavior can be partially explained by an interaction between CMC, fillers and polymer, with the formation of amide linkage between carboxyl part of CMC and amine end groups of polyamide, resulting in an increase in the complex viscosity of materials.

International audience; This article investigates and compares the effects of hydrothermal aging on carbon fibre / Elium™ thermoplastic composite and on carbon fibre / vinylester thermoset composite for marine application. Accelerated aging tests are performed by immersion in deionised water at 70 °C. Water diffusion, monitored by regular weighing, shows that both composites as well as Elium™ resin exhibit non-Fickian behaviour. Analytical models are proposed to fit the experimental curves and to identify and compare diffusion parameters. The aging effects on the microstructure are evaluated using SEM, while irreversibility of degradation mechanisms is investigated by desiccation tests. Mechanical tensile tests, performed before and after aging, show the slight impact of water on tensile modulus and tensile strengths for both materials. Furthermore, it was found that shear modulus and interlaminar shear strength undergo significant alteration related to irreversible physicochemical degradation of the matrix. Studied materials have shown different diffusion behaviours, but similar mechanical properties evolutions.

A calcium sulfoaluminate (CSA) cement has been characterised by X-ray diffraction and energy-dispersive X-ray spectroscopy analysis. Selective extraction methods have been used to improve detection limits for identification and quantitative measurements. Perovskites are present in the cement in the form of brownmillerite and a phase with the following average chemical composition Ca1·95Mg0·05Al0·29Ti0·39Fe1·03Si0·22O5·18. The zincite is known as a strong retarder for ordinary Portland cement (OPC), and its effect on the hydration of CSA cement was investigated using isothermal calorimetry, thermal analysis and X-ray diffraction. The low pH of the pore solution in the CSA cement compared to the OPC considerably reduces the solubility of zincite and, at an early age of hydration, zincite behaves as a filler in the CSA cement.

International audience; This work aims at evaluating the durability of a carbon fibre reinforced thermoplastic composite under different aging conditions. The absorption and desorption of deionised water in carbon fibre (CF) reinforced Elium composite material were measured gravimetrically over two different temperatures. Water uptake experimental data were fitted to a Langmuir type diffusion model in order to identify and compare diffusion parameters and kinetics and to evaluate their dependence to aging conditions. It was found that the temperature increase had a significant effect only on saturation water uptake. Water desorption after aging was modelled accurately using Fick's law and slight differences were found between model parameters. The effect of hydrothermal aging conditions and their reversibility were then evaluated by static and vibratory mechanical analysis. Results showed a slight and quasi-reversible reduction of longitudinal properties compared to shear properties at moderate aging temperature. While for higher aging temperature, the impact was found to be more significant and permanent on mechanical in-plane properties. Furthermore, static and modal results are confirmed by dynamic mechanical analysis, where the behaviour of studied material is differently affected by aging temperature, with a considerable increase in dried materials glass transition temperature.

International audience; This study evaluated the potential of using poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blends for fused filament fabrication (FFF) and assembly with pure PLA for biomedical applications. PLA/PCL binary blends were meltblended in a twin-screw extruder at different ratios (20/80 to 80/20) and then formed into filaments with a calibrated diameter for FFF. The microstructure, surface properties, and rheological and mechanical behaviors of the blends were assessed. The blends were immiscible but showed signs of adhesion between the phases. It was determined that the fibrillar morphology of inclusions for PLA/PCL ratios higher than 30/70 proved to be driven by the manufacturing process. The tensile mechanical behaviors of printed and injected samples were similar, and their Young's modulus was simulated using Halpin-Tsai and Mori Tanaka models based on the sample microstructure. The ductility of the blends was strongly driven by the behavior of its majority phase. Finally, specific samples were designed to characterize the tensile strength between PLA and its blends by entangling layers of both materials. The strength of the assembly was found to be dependent on the phase that was continuous and was governed by the strength and the viscosity of the blend.

International audience; The estimation of solid surface energy is generally obtained through the determination of liquid/solid contact angles. Many questions arise in the literature about the appropriate contact angle to use (dynamic, quasi-static or static, measured at a macro or a micro-scale). Theoretically, equilibrium contact angles should be inserted into equations to determine surface energy components. However, for powders or porous materials more issues arise, notably due to the imbibition of the liquid into the medium. An apparent contact angle can be obtained using wicking tests and the modified Washburn equation. Nonetheless, Washburn hypotheses are not always respected or no longer valid during wicking meaning that this procedure could not allow to determine contact angles. This study has the aim to propose a new simple method to determine the surface energy components of powders and porous media. An experimental protocol coupled to a modified Jurin law is proposed. This protocol was applied to lignin particles used as reinforcement in polylactic acid (PLA). Some treatments were performed on lignin to improve the adhesion with PLA and the modifications due to the treatments were characterized. Reliable surface energy and components of untreated and treated lignin were obtained revealing the efficiency of the proposed method.

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International audience; A boiling liquid expanding vapour explosion (BLEVE) is a physical explosion caused by a sudden rupture of a vessel containing superheated liquid. A BLEVE can occur with many types of fluids and is not an exclusive phenomenon for flammable liquefied gases such as propane or butane. Other superheated liquids suffering a fast depressurization at high temperature may entail a BLEVE, such as water in steam generation systems. Several pieces in literature suggest that superheated water may produce a BLEVE, but little experimental data can be found on that topic.The aim of this work was to perform water BLEVE tests with a 14 L pressure vessel designed on purpose to produce high superheated liquid water (290 °C; 75 bar) and to trigger a BLEVE through calibrated rupture disks. Pressure sensors were set in the vessel to measure the internal phase change pressure dynamics and other aerial overpressure sensors were put around the relief rupture disk to capture the blast wave. Temperature of water was also recorded, and a fast camera (Phantom V2512) was used to see the phenomenon.Data show clearly the pressure recovery due to rapid boiling in the vessel. Explosive boiling did not add additional internal pressure force on the containment. Two main blast waves were observed, they were strongly related with outlet orifice area but little dependant on filling ratio. The two phase jet reached a 20 m range.

International audience; By combining chemical and gamma radiation treatments, we show that it is possible to improve the interfacial adhesion between natural fibres and a non-polar and non-reactive matrix such as low density polyethylene (LDPE), and the resulting mechanical performances of their biocomposites. To this aim, flax fibres are first functionalized with octadecylphospho-nic acid (ODPA) and the quantity, effective grafting and localization of ODPA molecules on flax fibres are characterized by ICP-AES, solid state 31 P NMR and SEM-EDX. ODPA molecules are effectively grafted onto flax fibres at a content of roughly 2.5 wt% and mostly localized at the fibre surface. Moreover, contact angle measurements as well as water sorption kinetics give evidence for increased hydrophobic and oleophilic character of ODPA treated fibres. Pellets of LDPE/flax fibre biocomposites obtained by melt extrusion are then submitted to gamma radiation and processed by injection moulding. Based on Soxhlet extraction experiments and SEM observations, it is shown that LDPE cross-linking rate induced by gamma radiation is locally enhanced at the fibre/ma-trix interface, suggesting that regio-selective cross-linking occurred between LDPE chains and the alkyl chain of ODPA grafted on flax fibre surface. Consequently , the uniaxial tensile performances of the biocomposites are enhanced by this combined chemical and radiation-induced grafting approach, especially their ultimate properties (up to 40% increase in the work of rupture). These results evidence an enhanced interfacial adhesion that is also supported by more cohesive interfacial failure and higher work of rupture through in-situ micro-mechanical tensile SEM experiments.

International audience; The survival of a supermarket chain is heavily dependent on its capacity to maintain the loyalty of its customers. Proposing adequate products to customers is the issue of the store’s assortment. With tens thousands of products on shelves, designing the ideal assortment is theoretically a thorny combinatorial optimization problem. The approach we propose includes prior knowledge on the hierarchical organization of products by family to formalize the ideal assortment problem into a knapsack problem. The main difficulty of the optimization problem remains the estimation of the expected benefits associated to changes in the product range of products’ families. This estimate is based on the accounting results of similar stores. The definition of the similarity between two stores is then crucial. It is based on the prior knowledge on the hierarchical organization of products that allows approximate reasoning to compare any two stores and constitutes the major contribution of this paper.

Taraxacum officinale extract (TOE) has been tested for preventing the corrosion of cooling systems in desalination plants. The inhibition of corrosion effects has been characterized by chemical and electrochemical methods (Mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy) and surface observations. Tests on cooling systems were carried out in seawater environment. The presence of TOE in the re-circulation loop decreases the corrosion of carbon steel by adsorption of TOE compounds on the surface of metal pipes. The optimum TOE concentration was reached at 400 mg L−1 and the inhibition efficiency was higher than 94%. TOE allowed increasing the energy barrier of the corrosion process. SEM, FT-IR and UV spectra observations confirmed that TOE prevents corrosion attacks at the surface of the pipes. HPLC analyses identified the presence of saccharides, organic acids, phenol antioxidant and caffeic acid derivatives in TOE, which may be the active promoters of corrosion inhibition.

International audience; The results of a study of the mechanical properties of the honeycomb material made of polyamide-12, which consists of structural elements that repeat in three directions and have Schwartz primitive geometry, are presented. Samples in the form of a cube (size 30 × 30 × 30 mm) are obtained by layer-by-layer sintering of powder material on a 3D printer of selective laser sintering (SLS) type. Compression tests of samples with various geometry show that the strength of the samples increases with a decrease in the characteristic size of the repeating structural element. According to the calculations performed by the finite element method, this is caused by an increase in the dangerous sectional area. The possibility of a significant increase in the specific strength of the material while maintaining its density is shown.

International audience; Liquid Composite Moulding processes are considered as promising and effective to manufacture structure composite parts reinforced with synthetic and natural fabrics. The main novelty of this work is the estimation of capillary pressure (Pcap) for both fabrics at different fibre volume fractions (Vf) and with different liquids. From the previous works, the Pcap was defined as the equivalence between Washburn’s equation and Darcy’s law while our novel model for the capillary wicking could predict very well the swelling behaviour of natural fabrics. The combination of our Pcap definition and our novel model was explored in this study. Linear trends, thresholds and extremums of Pcap at different conditions were found for the first time. These results are relevant to estimate the importance of capillary effects during Liquid Composite Moulding processes and extremely valuable for numerical models at the fibrous scale to predict voids formation.

International audience; Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) is functionalized via radical grafting with 4-vinyl-1-cyclohexene 1,2-epoxide (VCHO) initiated using 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane. The existence of the epoxide group on the SEBS backbone is evidenced by 1H nuclear magnetic resonance. A size exclusion chromatography (SEC) study reveals some chain coupling, and this phenomenon is limited by controlling the quantities of peroxide and monomer reagents used during the radical grafting. Photo-crosslinking of SEBS-g-VCHO under ultraviolet irradiation in the presence of a cationic initiator is then successfully performed with resultant gel contents higher than 85%. Mechanical properties of SEBS and crosslinked materials are measured by tensile tests on thin films. On the one hand, those tests reveal a significant increase of Young's modulus of the crosslinked materials. On the other hand, the diminution of elongation at break is much more limited; crosslinked materials retain their elastomeric properties with an elongation at break greater than 200%. Finally, the photosensitive SEBS-g-VCHO is used to show the adhesion performance of the photo-crosslinking coating as well as a resin for the stereolithography process.

International audience

International audience; This work is focused on the preparation and the optimization of a biobased intumescent fire-retardant system (IFR) which was applied to a biopolymer such as PLA. This aliphatic biopolyester is obtained from agricultural plants and is recyclable and compostable in specific conditions. However, it has a poor thermal stability [1] and is very sensitive to hydrolysis [2]. In order to respect fire security standards, an IFR was designed using ammonium polyphosphate (APP), a common fire retardant and lignin which is a biobased by-product of the paper industry. Lignin has a good thermal stability and the ability to retard fire in composite materials by promoting the formation of char in association with APP [3]. The aim of the study is the optimization of the IFR and the chemical modification of lignin in order to prevent a trans-esterification between PLA and lignin that may break the polyester macromolecule. The first part of the study shows that an optimized ratio between APP and lignin is situated around 17/3. At this ratio, the IFR is more efficient with a significant reduction of the heat release rate (HRR) and a good fire retardancy capability (Figure 1). In addition, an encapsulated APP was also tested with lignin. The encapsulant improved the flame retardancy of the biocomposite with an enhancement of the char promotion. Finally, the last part of the work was focused on the chemical modification of lignin with esterification or phosphorylation. Chemical treatments showed an improvement of the quality of the PLA/lignin adhesion, due to the modification of the surface properties of lignin. The incorporation of phosphorus with lignin favors the intumescent reaction and the char promotion directly on the lignin particle. As a conclusion, lignin in association with APP was found to be efficient as IFR component for PLA, and beneficial as reinforcement for this polymer, applying adequate treatments to improve lignin surface properties and then the compatibility with PLA.

International audience; Current environmental concerns push towards more sustainable and local practices for biomass production. In this regard, agroforestry has been highlighted by researchers and policies as a highly efficient approach for carbon sequestration (between 1.5 and 4 t C/ha/year), and a sustainable alternative to deforestation with many agricultural benefits: deeper rooting of trees in soil, enhanced biomass productivity, crop fertilization... Agroforestry implies regular branch cuts that are processed into wood chips and mostly used as energy wood or soil mulching. New higher added-value chains could be considered such as reinforcements or specific molecules for bio-based materials and chemistry. Besides, since 90’s, Wood-Plastic Composites (WPCs) have experienced significant growth, particularly in building (decking & siding), and constitute the largest share of bio-based composites developed at an industrial scale. Nevertheless, the quality of WPCs and variability in their performance are major technological issues for their implementation in industrial applications. This could be related to the difficulty in tracing the various origin of wood fillers as well as the different processing steps, from wood drying and defibration process to composite manufacturing, that are not well controlled. Indeed, numerous interdependent parameters govern the final properties of WPCs, such as biochemical composition, presence of metallic and chemical contaminants (binders, wood treatment residues, varnishes, etc.), (micro)structure, thermal stability, mechanical properties of wood fillers, and the control of their milling/granulometry and further processing into composite materials. In this context, the development of quality-controlled agroforestry wood fillers in terms of granulometry (size and shape factor), chemical composition and physical (microstructure, mechanical) properties is therefore strategic for their implementation in wood-based products. This work investigates and evidences the influence of wood species (poplar, oak, walnut, chestnut)) and filler size and shape on the microstructure and mechanical properties of polypropylene (PP) / wood composites manufactured by extrusion/injection moulded. Moreover, wood from three recovery platforms in Brittany (mix of several species) was also investigated to evaluate the potential of existing agroforestry feedstocks.

National audience; Les élastomères thermoplastiques de la famille des copolymères poly(styrène-b-(éthylène-co-butylène)-b-styrène), dits SEBS, sont des matériaux de hautes performances en raison de leur microstructure particulière et de leur allongement à la rupture élevé. Ils sont largement utilisés comme matériaux absorbeurs de chocs, isolants de câbles ou dans des formulations d'adhésifs et de mastics. Ils présentent l’avantage de pouvoir être mis en œuvre par différents procédés (injection, extrusion, application en solution…).Bien que le SEBS soit largement utilisé aujourd'hui dans des applications de grande diffusion et des secteurs de pointe, seules quelques études se sont focalisées sur la modification du SEBS par greffage radicalaire du fait de sa sensibilité aux radicaux libres. Passaglia et Rosales ont rapporté en 2000 une dualité entre le degré de greffage d’un monomère comme l’anhydride maléïque et la β-scission, voire de réticulation des chaînes de SEBS [1,2]. Ces deux phénomènes conduisent à une dégradation très rapide des propriétés mécaniques du matériau et surtout de son allongement à la rupture. Aussi, accroître les applications potentielles du SEBS par modification de ses propriétés mécaniques reste un défi important.Dans cette étude, le SEBS a été fonctionnalisé par greffage radicalaire du 4-vinyl-1-cyclohexène 1,2-époxyde (VCHO), un monomère réactif par voie UV cationique grâce à son cycle époxyde cyclo-aliphatique. Ce greffage permet la réticulation ultérieure du SEBS sous rayonnement UV. À notre connaissance, c’est la première fois que la réactivité radicalaire du groupe vinyle du VCHO est mise en évidence, notamment par 1H-RMN, tout comme son greffage sur un polymère oléfinique. La photo-réticulation du SEBS-g-VCHO sous irradiation UV en présence d'un photoamorceur cationique a ensuite été conduite avec succès menant à des teneurs en gel supérieures à 85 %. Les propriétés mécaniques du SEBS-g-VCHO réticulé ont été caractérisées par des essais de traction sur films minces. Ces tests ont révélé une augmentation significative du module d'Young du SEBS-g-VCHO réticulé. Par ailleurs, les matériaux réticulés ont conservé leur comportement d’élastomères avec un allongement à la rupture supérieur à 200 %.Ces nouveaux matériaux pourraient donc être mis en œuvre pour la réalisation de revêtements ou de pièces obtenues en stéréolithographie 3D afin d’élargir la gamme d’élastomères réactifs actuellement utilisés dans ces applications.

International audience; The development of new sustainable routes towards better environmental footprint of composites for marine boatbuilding is motivated by the absence of eco-friendly and economically viable recycling techniques to deal with growing end-of-life thermoset boats waste and increasing restrictive legislation. Thermoplastic composites may offer the possibility to recover raw materials from retired parts, which could have a substantial environmental and economic benefit. This study investigates the feasibility of recovery and reuse of both reinforcement and matrix from a carbon fibre reinforced thermoplastic Elium composite. An original pyrolysis process allowed the depolymerisation of the acrylic matrix and recovery of clean carbon fibres and matrix monomer. Distillation was used to purify the monomer from impurities and a recycled Elium resin was synthesized and reused as matrix with long and aligned recycled carbon fibre reinforcement. The study of the morphological and composition differences at fibre scale resulted in concluding that sizing has been decomposed during depolymerisation process and only small traces of polymer were left on fibre surface. Virgin and recycled resin reinforced with carbon fibre laminates were produced by resin infusion. While tensile modulus, strength and strain at break were nearly unchanged, interlaminar shear strength results showed enhanced fibre-matrix interphase bonding. Dynamic mechanical analysis confirmed the good quality of recovered carbon fibres as well as similar virgin and re-polymerised resin properties. The new composite made from both recycled fibre and matrix could be used in the same application field.

International audience; A fire protective coating was developped by combining ammonium polyphosphate (APP) and sepiolite nanoparticles (SP) in Polyvinyl Alcohol (PVA). This coating was applied on a glass fibre/polyester composite substrate. Upon heat exposure, a thermal barrier was formed than enables to delay the backside temperature rise. The efficiency of the barrier was attributed to the reactivity between APP and sepiolite and the ability of the layer to reradiate heat.

This work highlights the possibility of obtaining peculiar morphologies by adding fumed silica into 80/20 polylactic acid/polyamide11 (PLA/PA11) blends. Two kinds of fumed silica (A200 and trimethoxyoctylsilane modified R805 fumed silica) were dispersed (by twin-screw extrusion, TSE) at a weight amount of 5% in neat PLA, neat PA11 and a 80/20 PLA/PA11 blend. Thermal Gravimetric Analysis (TGA) was used to verify this 5 wt % amount. Oscillatory shear rheology tests were conducted on all the formulations: (1) on neat polymer nanocomposites (PLASi5, PLASiR5, PA11Si5, PA11SiR5), and (2) on polymer blend nanocomposites (PLA80Si5 and PLA80SiR5). Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscope (STEM), Atomic Force Microscopy (AFM) characterizations and laser granulometry were conducted. Microscopic analysis performed on polymer blend nanocomposites evidenced a localization of A200 silica in the PA11 dispersed phase and R805 silica at the PLA/PA11 interface. Frequency sweep tests on neat polymer nanocomposites revealed a pronounced gel-like behavior for PLASi5 and PA11SiR5, evidencing a high dispersion of A200 in PLA and R805 in PA11. A yield behavior was also evidenced for both PLA80Si5 and PLA80SiR5 blends. For the blend nanocomposites, PA11 dispersed phases were elongated in the presence of A200 silica and a quasi-co-continuous morphology was observed for PLA80Si5, whereas PLA80SiR5 exhibits bridges of silica nanoparticles between the PA11 dispersed phases.

International audience; High speed imaging is applied for drop test on composite samples. The effect of optical blur on image correlation accuracy is described. Blur magnitude is tuned by decreasing the exposure time (at constant sensor sensitivity) for the same drop test series on flyspecked composite plates, while focus, aperture and 1:1 magnification are kept constant. Frame rate (80-20kfps) and lighting are changed while keeping the same image contrast. Results show correlation quality is already altered with subpixel blur. This study enables to define blur criterion in high-speed imaging and completes study about sampling rate effect in time resolved image correlation by high-speed imaging.

The use of bio-based concretes performed with lignocellulosic aggregates constitute an interesting solution for reducing the energy consumption, greenhouse gas emissions and CO2 generated by the building sector. Indeed, bio-based materials could be used as an alternative of traditional materials such as expended polystyrene and mineral resources (e.g. glass and rock wools) for insulation. Furthermore, these bio-based concretes are known for their interesting insulation properties, indeed they allow to enhance thermal properties of buildings and enables moisture management which lead to design efficient building materials. For this purpose, bio-based concrete using rice straw as aggregate are studied in this present work. The impact of the characteristics of rice straw particle (particle size distribution, bulk density, and water absorption capacity, etc.) on both the mechanical and thermal properties of the bio-based concrete are investigated. Five formulations of rice straw concrete are examined, compared and then classified in terms of insulation properties and mechanical properties. The assessments are based on the measurement of density and thermal conductivity. The variation of compressive strength in function of the characteristics (mean particle length) of rice straw particle are assessed and discussed. The investigation covers also the porosity and density. Tests are also carried out on agricultural by-products with a view to highlight their chemical, physical and structural proprieties. The results show that the use of large particles with low water absorption capacity induce lighter concretes with the density between 339 and 505 kg/m3 and lead to a high compressive strength with a high mechanical deformability. Furthermore, it appears that an increase in the average length of rice straw particle lead to decrease of thermal conductivity of bio-based concretes. It varies from 0.062 to 0.085 W/(m.K).

International audience; This study proposes a novel sepiolite-based Aquivion electrolyte membrane which could be operated at low relative humidity. In the study, it was discovered that the functionalization of sepiolite with fluorinated groups (i.e., -C7F15), named SEP-F, helps its dispersion in the composite membrane, compared with the use of natural sepiolite. The Aquivion/SEP-F composite membrane showed increased water uptake, thermo-mechanical and chemical stability as well as proton conductivity and decreased swelling compared with commercially available Nafion HP and pristine Aquivion. Their behavior in single cell MEA testing conditions was also assessed. Aquivion/SEP-F composite membrane can be an interesting alternative for low relative humidity operation of PEMFC (proton exchange membrane fuel cell).

The singular property of shrinkage is used in the packaging sector to wrap products. Polyethylene film products are mostly produced by either blown or cast film extrusion. During processing, under the effect of drawing, the molten polymer is stretched in one or two dimensions according to the cast or blown film extrusion. When the resulting solid film is subjected to a sudden increase in temperature, it shrinks as a result of the relaxation of polymer chains that were oriented under stress and frozen in a stretched state upon processing resulting in internal residual stresses. A general viscoelastic model in the framework of large strain has been used to predict the development of the internal residual stresses stored during the stretching stage of the process. Linear and branched polyethylenes (LLDPE, LDPE) were used as model matrices and additional blends (80/20%, 50/50% and 20/80% LDPE/LLDPE w/w) of pure resins were also studied. Moreover, as properties of stretched films are highly dependent on processing conditions, the influence of the draw ratio was also investigated. Contrasted mechanical response in strain of the LDPE and LLDPE films under stretching were observed and justified by differences in their rheological behavior due to long branch chains (LCB) in LDPE. The modeled ultimate stress stored in LDPE and LLDPE films was compared to the shrinkage stress measured by Dynamic Mechanical and Thermal Analysis (DMTA). Both stresses were found to be in the same order of magnitude which constitutes an interesting result for the prediction of heat-skrinkability of stretched polymer films.

International audience

International audience; The aim of this article is to investigate the optical properties of a recycled polymer during numerous processes. The effects of different process parameters (number of grinding-injection cycles, material temperature, mold temperature, and injection rate) on gloss and color properties of a buff-colored polypropylene containing 2wt%/wt of pigment was considered. The variations of properties are in the same range that is observed by changing processing parameters. It is found that the roughness is not able to explicate the variation of the optical properties for these variations of conditions. In addition, the optical properties of the skin layer of the injected parts are associated with the observed gloss and color variations. Moreover, the change of spherulite dimensions is related with optical changes.

Stone slate used for roofing is often considered as a key element of architectural heritage, especially in the French ‘‘Massif Central’’ region, where it contributes to the Mediterranean agropastoral cultural landscape of the “Causses and Cevennes” perimeter registered on the UNESCO World Heritage List. This material is subjected in service to severe and cycled climatic conditions (freeze-thaw) that may lead from mechanical damage to failure and thus compromise its use. In this paper, a damage assessment strategy of limestone roofing tiles samples during freeze-thaw cycles, based on the monitoring of their impulse vibration response, is proposed. Variations of the modal parameters such as resonant frequencies, damping ratios and mode shapes are analyzed through a 3D finite element model of each sample. This allows quantifying the loss of dynamic stiffness due to the ongoing damage and drawing comparisons between the studied materials in relation to their microstructural and mesostructural damages. Thus presence of pre-existing diagenetic features, such as stylolites (Ds in Nicholson classification), inside limestone tilestone with unimodal micropore, or with presence of high porosity volume, constitute weaknesses of the stone that can lead to damage.

In order to get new insights on cable behavior during real-scale fires, the gases released under incomplete combustion in pyrolysis combustion flow calorimeter were recorded for several PVC and halogen-free flame-retardant cables. Incomplete combustion was monitored by changing combustion temperature between 600 and 900 °C. Gases were identified using PCFC–FTIR coupling. Quantitative assessment of different gases produced during combustion was also carried out. It appears that larger amounts of unburnt gases are produced for PVC cable at low temperature (

International audience; Since the last decade, there has been an increasing demand for the design of more advanced functional materials. The integration of inorganic nanoparticles to polymer matrices is a powerful tool to confer their fascinating and complementary properties to the polymer materials. Among the different polymer nanocompos-ites, transparent nanocomposites are of particular interest due to their significance in a wide range of applications. To achieve a high level of transparency in the nanocomposites, it is necessary to minimize the aggre-gation of the nanoparticles that induce significant light scattering and thus hamper the application for transparent materials. The basic concepts of light scattering, the refractive index modulation and the methods to characterize the transparency of nanocomposites are provided to introduce this review. The fabrication of the transparent nanocomposites has been the subject of many efforts to develop methods to limit aggregation. To address this challenge, several methods have been implemented to control the polymerization process, the nanoparticle synthesis, and the polymer-nanoparticle interface together with the polymer casting or processing. The main methodologies developed to fabricate transparent nanocomposites are discussed according to four main categories: the blending of nanoparticles and polymer; the in-situ polymerization in the presence of pre-formed nanoparticles; the in-situ nanoparticle synthesis in a pre-formed polymer matrix; and finally the simultaneous polymerization and in-situ nanoparticle synthesis. The few studies dealing with casting of polymer solution loaded with core-shell nanoparticles are also discussed. In light of the literature on polymer nanocomposites, this review focuses on transparent nanocomposites with special attention given to the level of transparency and how this transparency is assessed for each study claiming transparency of the nanocom-posite. For each class of nanocomposites, it is of great importance to provide an overview of the different level of transparency according to the thickness of the polymer material. The second part of the review provides a thorough overview of the properties investigated in transparent nanocomposites with attention paid to the characterization of transparency. The transparent nanocomposites were described according to the targeted properties which are primarily the improvement of mechanical properties, thermal stability, barrier properties, magnetic properties and the optical properties. The optical properties have been the most thoroughly investigated due to the myriad inorganic nanoparticles exhibiting an excellent wide range of optical properties. Thus, the present review also describes the polymer/nanoparticle systems designed for the fabrication of transparent polymer nanocomposites with advanced optical properties: UV or IR-filtering properties, photoluminescence, ability to produce extreme refractive index, dichroism or non-linear optical properties.

The incorporation of glutaraldehyde crosslinked polyethylenimine (PEI) in algal beads (ABA/PEI) increases its Pd(II) sorption capacity. However, the large size of dispersed agglomerates introduces limitations of sorption performance in terms of availability and accessibility of reactive groups. The homogeneous incorporation of PEI in alginate/algal mixture prior to inotropic gelation and glutaraldehyde crosslinking (HABA/PEI) improves sorption performance: HABA/PEI beads have a higher maximum sorption capacity (1.49 ± 0.02 mmol g−1) than ABA/PEI (1.13 ± 0.03 mmol g−1), probably due to more uniform dispersion of PEI in HABA/PEI beads. The comparison of 5 consecutive cycles of sorption-desorption shows that HABA/PEI beads are physically stable with no mass loss, while ABA/PEI bead loses up to 30% of its weight. The potential of these materials as precursors for the synthesis of supported catalysts has been investigated. Pd(II) sorbed on ABA/PEI and HABA/PEI has been reduced to Pd(0) using hydrazine hydrate or hydrogen gas (generated in situ). A simple hydrogenation reaction of 3-nitrophenol (with sodium formate as hydrogen donor) was tested for comparing their catalytic properties. Catalytic tests show that HABA catalyst exhibits similar catalytic activity, but better stability and reusability compared with ABA catalyst. Their rate constants are lower than conventional nanostructured catalysts, probably due to intra-diffusion limitation.

International audience; The influence of an Interfacial Transition Zone on mechanical behavior of concrete has been established by many authors. Several experimental studies have highlighted the weak mechanical properties of Interfacial Transition Zone due mainly to higher porosity than other phases, or to the presence of initial damage at the interface between paste and aggregates. Thus, it is necessary to take this zone into account when modelling the mechanical behavior of concrete, particularly outside of the elastic domain. Various analytical or numerical methods have been proposed, and some of these replace the physical representation of an Interfacial Transition Zone, by an imperfect interface between paste and aggregates, and an adhesion model with specific mechanical properties. In this work a cohesive zone model coupling adhesion, friction and unilateral contact is applied to a finite element model of a cement paste-aggregate composite, designed to test interface mechanical properties. Cohesive zone model parameters are calibrated using an experimental study of the same composite, submitted to mechanical loading during hydration and leaching of cement paste. This numerical approach allows modelling of the mechanical behavior of a composite until the tensile strength is reached. Moreover evolution of cohesive zone model parameters during hydration and leaching, shows a partial adhesion on contact surfaces between cement paste and aggregate. This could explain initial interface damage.

Recycling of plastics is hindered by their important variety and strong incompatibility. However, sorting technologies bear costs and meet limits. Very high purities (&lt, 2 wt%) are difficult to reach. Yet, such rates may be detrimental to functional properties. In this work, an ABS matrix (major plastic in Waste of Electrical and Electronic Equipments) was filled with 4 wt% of PP to mimic impurities in ABS after recycling. PP-g-MA was introduced in the blend to improve the compatibility. A finite element model was developed from the mechanical behavior of each component. ABS and PP were individually characterized from tensile tests instrumented with photomechanics and their behaviors were modelled through a set of numerical parameters (elasto-visco-plasticity with a Gurson’s criterion behavior). Comparison between the determinist model results and the experimental data (strength, volumetric variation) shows that this type of modelling could be a predictive tool in order to anticipate composite mechanical properties and to understand micromechanisms of deformation (damage, cavitation). The main result is that PP introduced at 4 wt% into ABS does not alter the static mechanical properties despite polymers incompatibility. The addition of PP-g-MA modifies the local properties and possibly conduct to a premature breakage of the polymer blend.

International audience; With the development of dark polymers for industrial sorting technologies, economically profitable recycling of plastics from Waste Electrical and Electronical Equipment (WEEE) can be envisaged even in the presence of residual impurities. In ABS extracted from WEEE, PP is expected to be the more detrimental because of its important lack of compatibility. Hence, PP was incorporated to ABS at different rates (2 to 8 wt%) with a twin-screw extruder. PP was shown to exhibit a nodular morphology with an average diameter around 1–2 µm. Tensile properties were importantly diminished beyond 4 wt% but impact resistance was decreased even at 2 wt%. Both properties were strongly reduced as function of the contamination rate. Various potential compatibilizers for the ABS + 4 wt% PP system were evaluated: PPH-g-MA, PPC-g-MA, ABS-g-MA, TPE-g-MA, SEBS and PP-g-SAN. SEBS was found the most promising, leading to diminution of nodule sizes and also acting as an impact modifier. Finally, a Design Of Experiments using the Response Surface Methodology (DOE-RSM) was applied to visualize the impacts and interactions of extrusion temperature and screw speed on impact resistance of compatibilized and uncompatibilized ABS + 4 wt% PP systems. Resilience improvements were obtained for the uncompatibilized system and interactions between extrusion parameters and compatibilizers were noticed.

Environmental impact assessment studies are mandatory for major industrial or infrastructure projects in most countries. These studies are usually limited to on-site impacts during exploitation but do not consider indirect impacts generated off-site or those concerning other steps of the project, including dismantling. National regulations in various countries have recently begun to include these neglected impacts to obtain a better appreciation of project trade-offs. Several scientists have highlighted the substantial potential of using the life cycle assessment methodology to increase the level of detail and completeness of environmental impact assessment (EIA) studies. Even if mining activities are known to produce significant local impacts, their consequences outside an extraction site have not yet been well documented. The implementation of the life cycle assessment (LCA) methodology in the EIA procedure has been carried out in a Au mining project by separating on-site and off-site impacts during the entire life cycle of the mine from prospection to site restoration following the end of exploitation. Mining projects occur over large time periods and require diverse materials and processes. The main difficulty of such analysis is the data collection that needs to be extrapolated for some of the activities. Even with these limitations, the Afema case study highlighted the significant share of off-site impacts (from a spatial perspective) and the major contribution of the exploitation phase of the mine (from a temporal perspective). Operating activities, especially excavation, ore, and waste rock transportation, blasting, ore processing, and tailing treatments, are the main impacts produced during the exploitation phase and are involved in climate change, particulate matter formation, and land destruction. Therefore, this standardized LCA method should be recommended by the regulatory authorities for use in EIA procedures. Integr Environ Assess Manag 2021;17:465-479. © 2020 SETAC.

International audience; The Cretaceous of southern France is characterized by a long erosional hiatus, outlined with bauxite deposits, which represent the only remaining sedimentary record of a key period for geodynamic reconstructions. Detrital zircons from allochthonous karst bauxites of Languedoc (Southern France) have been dated using LA‐ICP‐MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry), in order to specify the age of deposition and to constrain the provenance of the weathered material. We analysed 671 single detrital zircons grains from 3 karst bauxitic basins, stretching from close to the Variscan Montagne Noire to the present‐day Mediterranean Sea. Analytical results provide Variscan (300‐350 Ma) and Late Proterozoic (550‐700 Ma) ages as primary groups. In addition, Middle‐, Late Proterozoic and Early Archean (oldest grain at 3.55 Ga) represent significant groups. Mid‐Cretaceous zircons (118‐113 Ma) provide a pooled age of 115.5 ± 3.8 Ma, which constitutes the maximum age for bauxite deposition. Results also suggest a dual source for the Languedoc bauxite: one generalized sedimentary source of regional extent and a localised source in the Variscan basement structural high, that has been progressively unroofed during Albian. Integration of these new findings with previously published thermochronological data support the presence of an Early Cretaceous marly cover on the Variscan basement, which has been weathered and then removed during the Albian. The Languedoc bauxite provide a spatial and temporal link between the uplift of southern French Massif Central to the north, and the Pyrenean rift and its eastward extension to the south. These new results allow to constrain the timing and distribution of uplift/subsidence during the mid‐Cretaceous events in relation with the motion of the Iberian plate relative to Eurasia.

International audience; The molecular architecture and rheological behavior of linear and branched polybutylene succinate blends have been investigated using size-exclusion chromatography, small-amplitude oscillatory shear and extensional rheometry, in view of their processing using cast and blown extrusion. Dynamic viscoelastic properties indicate that a higher branched polybutylene succinate amount in the blend increases the relaxation time due to an increased long-chain branching degree. Branched polybutylene succinate exhibits pronounced strain hardening under uniaxial elongation, which is known to improve processability. Under extensional flow, the 50/50 wt % blend exhibits the same behavior as linear polybutylene succinate.

International audience; A poly(vinyl alcohol) (PVA)-based coating containing ammonium polyphosphate (APP) and sepiolite nanofillers (SP) and supported by a glass fabric was developed to fire-protect a glass-fiber-reinforced unsaturated-polyester-based (UP) polymer (GFRP). The fire behavior and thermal stability of the PVA coatings were characterized using thermogravimetric analysis (TGA) and a cone calorimeter. The coatings’ residues were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results from the cone calorimeter showed that the addition of sepiolite significantly improves the flame retardancy of PVA/APP/SP coatings. The addition of both additives promoted the formation of a cohesive layer composed of a silico-phosphate structure resulting from the reactivity between APP and SP. The fire resistance of the composite laminate protected by PVA coatings was evaluated using a cone calorimeter by measuring the temperature of the back face. Photogrammetry was used to assess the swelling of residues after heat exposure. The interaction between APP and SP in PVA coating leads to the formation of an effective thermal barrier layer. The presence of SP reduces the layer expansion but greatly decreases the backside temperature during the initial period of exposure. The effect was assigned to high thermal stability of the layer and its ability to dissipate heat by re-radiation.

International audience; This paper aims to investigate the effect of the settling behaviour of sediment particles during resuspension on the mobilisation of pollutants such as polycyclic aromatic hydrocarbons (PAHs). Sediments were collected in different areas (basin, channel, beach) of a Mediterranean harbour, located in the south of France (the Grau du Roi harbour), and then separated into different size fractions: large (80–1000 μm), intermediate (40–80 μm), and fine (< 40 μm). Total PAHs concentrations in the initial sediment ranged from 320 to 1043 μg kg-1. Study of the settling behaviour of the PAH-contaminated sediment revealed two sedimentation regimes: sedimentation by mass, which exhibits a sharp interface between the supernatant and the deposit, and sedimentation by clarification with no interface. It appears that sediment particles settle either by the clarification regime or by a combination of the two sedimentation regimes, depending on the size fraction. Particle size distribution monitoring during the settling process allowed the identification of sediment particles less than 20 μm which remain in the water column up to 20 min after resuspension and appear to be the ones that can potentially mobilise PAHs.

International audience; An environmentally friendly approach, which consists in coupling a dielectric barrier discharge (DBD) based atmospheric plasma treatment with a coating of an aqueous phase polyurethane dispersion (PUD) containing blocked polyisocyanates, is proposed to improve the adhesion of a thermoplastic polyurethane (TPU) film onto a poly-(ethylene terephthalate) (PET) textile fabric. In this study, a screening digital design of experiment plan (DOE) was developed to determine the influence of process parameters on the adhesion between film and fabric and to evaluate the best possible adhesion value. The process parameters considered are: the dielectric barrier discharge power, the speed of the fabric undergoing the treatment, the concentration of polyisocyanates (NCO) in the PUD and the air gap. The adhesion was measured by a peeling test and further scanning electron microscope observations were carried out. Results showed that an increase of both the processing power and the NCO content in PUD, as well as the decrease in the DBD speed, had a positive effect on the adhesion. In addition, X-ray photoelectron spectroscopy and contact angle measurements demonstrated an increase in the oxygen/carbon atomic percentage ratio between the reference fabric and the treated fabric. Thus, the calibrated oxidation of the PET treated with DBD plasma treatment leads to a greater chemical and physical interaction with the TPU film, which results in better film-fabric adhesion.

International audience; Structural composite materials with good impact resistance are required in several industrial sectors to design parts submitted to crashes or falling objects. This work investigates the impact behaviour of flax fabrics-epoxy and commingled flax-polypropylene (PP) fibres composite plates manufactured using compression moulding process. An instrumented drop tower was used to conduct low velocity impact tests at several energies and high-speed imaging coupled with DIC analysis was used to assess the damage evolution. A crack-tracking algorithm was implemented in ImageJ to identify the initiation and propagation of cracks. A comparison of the force-displacement histories and high-speed camera results for both composites were used to identify the different modes of damage and the critical energy for complete penetration. The proposed method is able to depict the successive events that lead to the breakage of biocomposites and it will be a valuable tool to investigate the impact behaviour of other materials as well.

Une approche par éléments finis cohésifs-volumétriques, tenant compte des propriétés mécaniques de la zone de transition interfaciale (ITZ), est utilisée pour étudier le comportement mécanique du béton lors d'un essai de compression uniaxiale. Dans ce travail, un modèle géométrique bidimensionnel à l'échelle mésoscopique du béton numérique a été considéré. Les échantillons obtenus sont maillés à l'aide du logiciel GMSH avec une méthode de Delaunay. Les résultats des simulations à l’aide du Modèle de Zones Cohésives Frottantes (MZCF) permettent, à travers une étude de criblage de type Hadamard, d’apporter des éléments de réponses concernant les facteurs les plus influents et leur contribution à la résistance maximale du béton en compression uniaxiale., Academic Journal of Civil Engineering, Vol 38 No 1 (2020): Special Issue - RUGC 2020 Marrakech

This text presents two Artificial Intelligence (AI) approaches to a non-computer audience. Non-specialist researchers wishing to deepen their knowledge in this field will find a structured review and a classification of the various reference works in AI according to the two usual approaches. The first one is the core of Cognitive Sciences and assumes an autonomous cognitive level. The second one focuses on interactions and assumes that cognition is linked to an organism inserted in a particular situation with a specific configuration. For each approach, we also propose an analysis of their relationship to natural intelligence and natural cognition. Then we present the intelligence of objects which put into perspective an organizational intelligence., Ce texte présente deux approches de l’intelligence artificielle (IA) pour un public non informaticien. Les chercheurs non spécialistes désireux d’approfondir leurs connaissances sur ce domaine y trouveront une recension structurée et une classification des différents travaux de référence en IA selon les deux approches usuelles. La première est le cœur des sciences cognitives et suppose un niveau cognitif autonome. La seconde s’intéresse aux interactions et suppose que la cognition est liée à un organisme inséré dans une situation particulière avec une configuration spécifique. Pour chacune des approches, nous proposons également une analyse de leur relation à l’intelligence et la cognition naturelles. Puis nous présentons l’intelligence des objets qui met en perspective une intelligence organisationnelle.

International audience; This work is focused on the modification of the interphase zone in short flax fibres / polypropylene (PP) composites by a bio-inspired modification of fibres called “nanostructuration” that uses the adsorption of biomass by-products, i.e. cellulose nanocrystals (CNC) and xyloglucan (XG), to create hierarchical flax fibres. The wettability and interfacial adhesion study reveals a strong decrease in the polar character of CNC modified flax fibres, hence increasing the work of adhesion with PP. Moreover, combining XG/CNC modified interphases with MAPP coupling agent enhances the ultimate mechanical properties of biocomposites with higher tensile strength and work of rupture, and modifies failure mechanisms as revealed by in situ micro-mechanical tensile SEM experiments. Bio-based hierarchical composites inspired by naturally occurring nanostructures open a new path for the development of sustainable composites with enhanced structural properties.

International audience; Interest in eco-composites incorporating elements from recycling is growing to reduce the carbon footprint of final products. Therefore, the characterisation surface properties of recycled fibres is of first importance. However, in order to maximise the service properties and facilitate their development, chemical surface treatments can be made in order to improve fibres compatibility with resins. For a better understanding of the behaviour of these new reinforcements during Liquid Composite Moulding processes (LCM), surface analysis and wetting properties are studied. However, this type of analysis, using the Owens and Wendt relation and based on tensiometric methods, requires special procedures, specifically for estimation of the contact angle. Based on two tensiometric methods, carbon and basalt fibres with different sizing are characterised in first approach, in order to be able to address recycled materials in further studies. The main contribution of this study is to evaluate the error in surface energy and its components determination associated to the measurement of an alleged equilibrium contact angle deriving from static or quasi-static data.

International audience; This article reports on a new method to elaborate and conduct the safety demonstration phase for Nuclear infrastructures in phase with System Engineering principles. More particularly, this method focus on helping and guiding engineers involved in nuclear safety demonstration into a better assessment considering the increasing complexity and the expectations from the licensing owner who has to accommodate for any new nuclear project. As a first part of this method, this article claims that MBSE coupled to Natural Language Processing (NLP) and Artificial Intelligence (AI) is facilitating the Nuclear safety demonstration process and allowing to early prevent for any issues the project may face during the design, construction, commissioning and exploitation phases.

National audience; Les démarches en faveur de l’économie circulaire, attendues par le société civile et pilotées par les leviers législatifs,financiers, … nécessitent, pour leurs mises en œuvre, le développement d’une expertise tant en matière de compétences (et donc de compétences) que de recherche. C’est à ce défi que doivent répondre les écoles d’ingénieurs intervenantau croisement de ces domaines (entreprises, recherche, enseignement).

International audience; Skills, commitment, and motivation of hospital workers are essential to cope with sanitary crisis (Barasa et al., 2018) such as COVID-19 pandemic. However, most research on the preparation of hospital workers for sanitary crisis shows a mismatch between their level of preparedness and their perceived preparedness and the estimated needs to manage these situations (Gowing et al., 2017; Labrague et al., 2018). In this context, it is crucial to understand how these individuals perceived their readiness to manage these situations and not only their preparedness level. Social psychology can provide clues for understanding the readiness perception (Mishra & Mazumdar, 2015). This study aims to explore hospital workers readiness perception to manage a sanitary crisis upcoming (COVID19 pandemic) and determinants of this perception. 408 French hospital workers respond to an online survey containing 11 items about COVID-19. Variables studied concern perception of personal preparedness, colleagues preparedness, and institutional preparedness. Results show that hospital workers have a relatively low readiness perception to manage COVID-19 before it came out. This study proposed a model explaining personal readiness perception to manage COVID-19, most important variables are: Colleague hospital service’s (β=.37***), personal preparation perception (β=.29***), perception of hospital human resources sufficient (β=.22**), perceived capacity for professional action (β=.097***), and perception of personal skills as sufficient ( β=.11**). These results show that personal preparedness is not enough to feel ready, there is other essential variables. This study shows that the perception of personal readiness is a complex process which deserves a psycho-social study combining individual and collective variables. For practice, these results suggest that the preparation must therefore be based on the collective and not only on the individual.

National audience; À l’échelle mondiale, le lien entre changements climatiques et ressources en eau est un sujet d’intérêt, car les premiers sont susceptibles d’augmenter la fréquence et l’intensité des événements extrêmes (sécheresses, précipitations, inondations) et d’affecter ainsi la dynamique des hydrosystèmes de surface et souterrains. À une échelle plus locale,au sud de la France, les Gardons supportent (ou ont historiquement supporté) différentes activités humaines tout au long de leur parcours. À l’heure actuelle ces différents évènements sont étudiés quantitativement, essentiellement pour des aspects de gestion des risques naturels (prévision des crues éclairs et sécheresse). En revanche, les aspects qualitatifs de la ressource ainsi que leur variabilité sont beaucoup plus mal connus. La variabilité de la qualité de l’eau peut cependant avoir des conséquences importantes en termes d’usages, avec une eau de qualité dégradée qui peut présenter des impacts sanitaires ou environnementaux. Une meilleure connaissance des conséquences des changements climatiques sur la qualité des eaux et, par répercussion sur les usages de l’eau est donc nécessaire. La conception et la mise en œuvre de mesures d’adaptation, ainsi que l’évaluation de leurs effets sur la santé humaine, les écosystèmes et la disponibilité de la ressource en eau pour les générations futures s’avère indispensable.

Issu de : ITISE 2019 - International Conference on Time Series and Forecasting, Granada, Spain, 25-27 September 2019; International audience; Flash floods frequently hit Southern France and cause heavy damages and fatalities. To enhance persons and goods safety, official flood forecasting services in France need accurate information and efficient models to optimize their decisions and policy in crisis management. Their forecasting is a serious challenge as heavy rainfalls that cause such floods are very heterogeneous in time and space. Such phenomena are typically nonlinear and more complex than classical flood events. This analysis had led to consider complementary alternatives to enhance the management of such situations. For decades, artificial neural networks have been proved very efficient to model nonlinear phenomena, particularly rainfall-discharge relations in various types of basins. They are applied in this study with two main goals: first, modeling flash floods on the Gardon de Mialet basin (Southern France); second, extract internal information from the model by using the KnoX: knowledge extraction method to provide new ways to improve models. The first analysis shows that the kind of nonlinear predictor strongly influences the representation of information, e.g., the main influent variable (rainfall) is more important in the recurrent and static models than in the feed-forward one. For understanding “long-term” flash floods genesis, recurrent and static models appear thus as better candidates, despite their lower performance. Besides, the distribution of weights linking the exogenous variables to the first layer of neurons is consistent with the physical considerations about spatial distribution of rainfall and response time of the hydrological system.