Portail des publications scientifiques IMT Mines Alès
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Accelerated ageing of a pultruded FRP composites PA6/GF
No full textInternational audienceNowadays, mobility is experiencing numerous transformations driven by the need to reduce carbon footprint. The INFRAlight project aims to develop an environmentally friendly composite railway infrastructure to reduce the carbon footprint in economic development. Rails are subjected to severe natural and mechanical weather conditions such as temperature variations, relative humidity, UV radiation. Therefore, the study of durability under severe service conditions is essential to the industrial exploitation of these materials. One of the materials considered for this application is a pultruded fibre-reinforced plastic (FRP) made of polyamide 6 (PA6) and glass fibres (GF). Literature shows that the durability of pultruded composite materials is still an understudied topic. However, several studies have shown that PA6 polymers are sensitive to moisture, leading to changes in their physicochemical properties and a decrease in their mechanical properties. In this study, accelerated hygrothermal ageing at 70 °C and 80 %RH was applied to the PA6/GF pultruded composites. The results show a decrease in mechanical properties during water absorption, followed by a recovery upon drying, highlighting the reversibility of the ageing process.Viscoelastic characterisation from vibration analysis complement these results to understand the effect of moisture on the material
Post-polio syndrome is not a dysimmune condition
No full textInternational audienceBackground: Poliomyelitis is a global disabling disease affecting 12-20 million of people. Post poliomyelitis syndrome (PPS) may affect up to 80% of polio survivors: increased muscle weakness, pain, fatigue, functional decline. It relies on aging of an impaired neuro-muscular system with ongoing denervation processes. A late involvement of humoral or cellular pro-inflammatory phenomena is also suspected.Aim: To assess the dysimmune hypothesis of PPS by comparing lymphocyte subpopulations and humoral immune factors between PPS patients and controls.Design: Cross-sectional study.Setting: Montpellier University Hospital.Population: Forty-seven PPS and 27 healthy controls.Methods: PPS patients and controls were compared on their lymphocyte subpopulations and humoral immune factors (IL-1β, IL-6, IL-8, IL-17, IL-21, IL-22, IL-23, IFN-γ, TNF-α, GM-CSF, RANTES, MCP1, MIP-3a, IL-10, TGF-β, IL4, IL13). Patients were further compared according to their dominant clinical symptoms. Sample size guaranteed a power >90% for all comparisons.Results: PPS patients and controls were comparable in gender, age and corpulence. Most patients had lower limb motor sequelae (N.=45, 95.7%), a minority had upper limb motor impairment (N.=16, 34.0%). Forty-five were able to walk (94%), 35/45 with technical aids. The median of the two-minute walking test was 110 meters (interquartile range 55; 132). Eighteen (38%) required help in their daily life. Their quality of life was low (SF36). All described an increased muscular weakness, 40 (85%) a general fatigue, and 39 (83%) muscular or joint pain. Blood count, serum electrolytes, T and B lymphocyte subpopulations and cytokines were comparable between patients and controls, except for creatine phospho kinase that was significantly higher in PPS patients. None of these variables differed between the 20/47 patients whose late main symptoms were pain or fatigue, and other patients.Conclusions: Our results suggest that PPS is not a dysimmune disease.Clinical rehabilitation impact: Our results do not sustain immunotherapy for PPS. Our work suggest that PPS may be mostly linked to physiological age-related phenomena in a disabled neuromuscular condition. Thus, our results emphasize the role of prevention and elimination of aggravating factors to avoid late functional worsening, and the importance of rehabilitation programs that should be adapted to patients' specific conditions
How effective is transcranial direct current stimulation?
No full textInternational audienceGerrit Burkhardt and colleagues reported that the use of transcranial direct current stimulation (tDCS) as an additional treatment to stableselective serotonin reuptake inhibitor pharmacotherapy did not elicit further antidepressant effects in patients with major depressive disorder (MDD) [...]
Flash flood and vigilance forecasting of a complex, anthropogenic karst hydrosystem using neural networks. Application to the Las coastal river at Toulon (South-East France)
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Cellulose nanocrystals as reinforcements in thermoplastic Composites: effect of processing route on dispersion
No full textInternational audienceCellulose nanomaterials, such as cellulose nanocrystals (CNC), are expected to play a major role in the current environmental and societal transition towards a greater use of bioresources for materials applications. Due to their low density, high specific surface area and high Young's modulus, these nanomaterials have a great potential as sustainable, high-performance fillers for the development of materials with tunable rheological, thermo-mechanical, optical and barrier properties [1]. They are currently used mainly in paper manufacturing, packaging, membranes and bioengineering.As with other nanoparticles, the dispersion of CNM in thermoplastic polymers remains a huge challenge for the development of high-performance polymer nanocomposites. In the literature, several processing methods have been studied to improve their dispersion and the mechanical properties of the nanocomposites, using solvent-based, melt processes and other more innovative processes such as chilled extrusion or wet compounding with various thermoplastic polymers as well as physico-chemical and processing aids [2], [3]. However, it has been shown that the different processes seem to have a similar impact on mechanical improvements, and therefore potentially on CNM dispersion, with the exception of the Kyoto process [3].In this work, a common system to different preparation routes, based on thermoplastic polyvinyl alcohol (PVA) and CNC, is used to study the operating conditions and parameters. The different processing methods were compared on a laboratory scale: from conventional solvent and melt routes, to more recent hybrid routes. With the aim to identify the key steps in obtaining a good dispersion of CNC that best improves the mechanical properties of the final composite. The impact of the processing method on the CNC dispersion in PVA is discussed, in particular by means of rheological, mechanical and microstructural analyses of PVA/CNC composites
Vieillissement accéléré des fibres naturelles et de leurs composites : une étude comparative
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Effect of Flax Shive Particle Size on Microstructure and Mechanical Behaviour of Injection-Moulded Thermoplastic Biocomposites
No full textNational audienceFlax shive (FS) is the predominant by-product of flax fibre production, representing around 50% of the weight of the dry flax stem. Recent studies [1] have shown that FS initial granulometry affects the tensile properties of the reinforced composite. Therefore, our study aims to investigate the influence of FS granulometry on the microstructure and mechanical properties of FS/Polypropylene (PP) injected composites. Various FS granulometries (FS-0-200, FS-200-315, FS-315-500, FS-200-500, FS-500-800 and FS-800-1600 µm) were prepared and incorporated into PP composites with fibre weight fraction ranging from 10 to 40%, using extrusion and injection moulding. An optimal quantity of Maleic Anhydride Polypropylene (MAPP) was used as a compatibilizer in the composites. X-ray tomography was conducted on composites reinforced with 10% wt. of FS-200-500 (Figure 1) and FS-800-1600, providing insights into the impact of FS granulometry on FS orientation and its distribution in the composite microstructure. The dimensions and aspect ratio of the FS particles were measured using a 2D scanner after solvent extraction. The results reveal that the maximum aspect ratio of the FS after processing is reached by the medium-size particles FS-200-315, with deviations in particle size leading to a decrease in its aspect ratio. Additionally, it was observed that FS-200-500 tends to be more oriented toward the injection flow compared to FS-800-1600. Composites reinforced with 30%wt. of FS-200-315 demonstrate a significant enhancement, with Young's modulus increasing by 19% (from 2964 MPa to 3519 MPa) and ultimate tensile strength by 26% (from 32.1 MPa to 40.3 MPa), compared to those reinforced with 30%wt. of FS-800-1600. The elastic properties of the composite were modelled using the Mori-Tanaka model based on the investigated microstructural parameters, allowing us to back-calculate the FS Young’s modulus. The Mori-Tanaka model shows that there is a variation in Young’s Modulus among the different FS granulometry within a range between 14 and 29 GPa (Figure 2), which is in the same range as estimated using analytical modeling in the literature: 27.9 GPa [2] and 22.2 GPa [3]
Pneumatically Actuated Soft Robotic Hand and Wrist Exoskeleton for Motion Assistance in Rehabilitation
No full textInternational audienceExoskeletons are being explored for assisting motion therapy for neurological impairment-related rehabilitation. Soft robotic exoskeletons are gaining more attention for upper-extremity applications due to their simplistic actuation mechanisms and compliant nature. To regain fine motor hand functions, it is desired to have both hand and wrist motions in a coordinated fashion, as most daily living tasks require a combination of both hand and wrist joint motions. However, a soft robotic exoskeleton with hand and wrist motion together is an underdeveloped area. This paper presents a pneumatically actuated soft robotic exoskeleton designed to provide coordinated assistive motion to the hand and wrist joints using PD-based feedback control. The results showed the potential of the exoskeleton to provide flexion/extension rehabilitation exercises and task-oriented rehabilitation practices. Additionally, the results have confirmed that the implemented PD control ensures that the exoskeleton reaches the targeted angular trajectories and velocities. Two modes, full and partial assistance, were successfully tested to verify the ability of the exoskeleton to accommodate varying levels of impairment
Interactions son/mouvement: indiçage rythmique et sonification
No full textInternational audienceDans le domaine de la santé, l’utilisation interactive de contenus sonores émerge comme technique innovante de stimulation de l’appareil sensori-moteur. Dans cet atelier seront présentés des travaux menés au sein de l’unité de recherche EuroMov DHM, dans un premier temps à travers l’utilisation de l’indiçage rythmique et de l’étude de la synchronisation, puis via deux mises en œuvre expérimentales de techniques de sonification du mouvement.Le premier dispositif, appelé HearMyHarm, a été conçu dans le cadre du traitement de la maladie de Parkinson. L’approche retenue est celle d’un retour sonore continu dont l’objectif est de permettre aux utilisateurs de prendre conscience de la position de leur bras et de l’amplitude des mouvements réalisés. Le développement d’un premier prototype a été l’occasion de tester deux systèmes de capture du mouvement (Qualisys et Movella Xsens), et de concevoir un système de synthèse sonore lié aux coordonnées biomécaniques du mouvement.Le deuxième dispositif est développé dans le cadre du projet européen Sharespace. Ce projet propose la création et l'exploration d'espaces virtuels et hybrides englobant une approche sensorimotrice des interactions sociales. Dans le cadre du scénario « health », un travail est en cours avec l’hôpital Vall d’Hebron de Barcelone pour le traitement de la lombalgie. L’utilisation du son au coeur de l’espace virtuel dans lequel le patient réalise des mouvements thérapeutiques ouvre de nombreuses perspectives de stimulations et de retours pour l’utilisateur, sur des aspects motivationnels et posturaux
Electrical properties of graphene/multiphase polymer nanocomposites: A review
No full textInternational audienceGraphene and their derivatives exhibit interesting properties (mechanical properties, electrical and thermal conductivities). When incorporated into polymer matrices, many applications are possible in fields like electronics, medicine, transportation. The goal of the present review is to highlight how graphene can influence the electrical properties of polymer nanocomposites. The first part explains the peculiar structure of graphene, the main ways to synthesize graphene and the influence on electrical conductivity. In this first part, it is also explained how orientation and alignment of graphene platelets or the presence of a second filler can influence the percolation threshold or electrical conductivity of a monophase polymer nanocomposite. Finally, in this first part, we present some generalities on the enhancement of electrical properties by chemical treatments performed on the graphene. The aim of the second part of this review is to show the effect of the incorporation of graphene into immiscible polymer blends on the microstructures and on the electrical properties. Especially, we focus on the concept of selective localization of nanoparticles into a blend: how to predict the localization of graphene and how to tailor the localization by chemical and kinetics factors. Several graphs were drawn, based on the data of 73 publications, to exhibit the influence of different parameters on the electrical conductivity (in S.cm−1) of graphene based polymer blend nanocomposites. Finally, the last part of this review is dedicated to the electrical applications of graphene-based polymer blend nanocomposites