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Advances in the Circularity of Polymeric and Composite Materials
No full textPolymeric and composite materials are ubiquitous today. However, to improve their sustainability, it is of paramount importance to make sure that their waste does not end up in landfill or in the environment, and to find ways to recover and reuse these materials in useful and profitable applications. To contribute to building a resource-efficient future, it has become essential to put them in the loop of a more circular economy.Eco-design, including design for recycling, has become the watchword, with several recycling techniques available and competing to achieve this ambitious goal. There is also an increasing number of attempts to reuse constitutive products recovered that way by reincorporating them into new materials or high value-added applications. Which methods achieve which objectives, however, and which make sense for various feedstocks?This Special Issue welcomes papers on the latest advances and development of recycling, recovery, and reuse of polymeric and composite materials. Suggested contributions may address materials, processing, sorting, design, performance, or application issues, with either experimental or numerical approaches
Laser transmission welding of PEKK: Influence of material properties and process parameters on the weld strength
No full textInternational audienceAbstract. Laser transmission welding (LTW) is a suitable process for assembling thermoplastic materials. This joining process is use to assembly most thermoplastics, but high-performance thermoplastics, such as polyetherketoneketone (PEKK), have received less attention until now. The present work deals with joining PEKK parts by LTW in amorphous over semi-crystalline state configuration. The optical properties of amorphous and semi-crystalline states were measured. The effect of the upper part thickness (2 or 4 mm) and those of the laser power reaching the interface was assessed through the determination of the heat affected zone (HAZ) dimensions and the mechanical resistance of the bonds. Single lap shear (SLS) tests were conducted to investigate the influence of the process parameters on the interfacial strength and to validate the weld quality. The highest LSS is obtained around 60 MPa. When increasing the laser power, the dimensions of the HAZ increase, and the mechanical strength decreases
Experimental characterization and numerical modeling of a viscoelastic expandable epoxy foam: Time–temperature transformation and time–temperature equivalence diagrams
No full textInternational audienceAn expandable and Fire, Smoke, and Toxicity (FST) compliant epoxy foam is proposed as an interesting alternative to Nomex® honeycomb cores for the development of Multi-Functional Structures (MFS). The paper first analyzes the processing conditions using several experimental techniques as differential scanning calorimetry (DSC), rheology, and expansion in a closed volume in order to evaluate the reaction kinetics, the chemorheological behavior, and the expansion kinetics of the material. The experimental data are used to identify several empirical models describing the material processing behavior and finally plotting the isothermal time–temperature transformation (TTT) diagram. A typical curing cycle for the foam is used to describe the evolution of the material parameters during the curing process. The fully cured foam is then characterized using optical and laser microscopy in order to identify its cell size distribution and density. Quasi-static and dynamic machines are used to evaluate its mechanical and dynamical properties. The time–temperature equivalence is finally used to plot the master's curves of the material, representing the evolution of the material viscoelastic properties as a function of the frequency
Dynamic characterization approach for the investigation of microstructural changes in clay-based materials during firing
No full textInternational audienceThis work aims to understand the mechanisms occurring during the microstructural transformation of clay-based mixtures. For that, the combination of various standard and advanced characterization techniques was used. This original approach allowed an outstanding description of complex mechanisms involved during the firing, bringing new insights in regards to the state-of-the-art. Thus, the formation of viscous glassy phases and the associated effects in terms of densification acceleration were particularly revealed by following the damping of Acoustic Resonance (AR) signals and by dynamic high-temperature Scanning Electron Microscopy (SEM). Further STEM-EDX (Scanning Transmission Electron Microscopy Coupled with Energy Dispersive X-ray) analyses revealed that the glassy phase resulting from the solidification of the viscous phase is predominantly composed of silicon, aluminum, oxygen, and potassium. This study also evidenced that the behavior of a binary clay-based mixture was not always described by a mixing law model
How nucleating particles migration affects the fractionated crystallization of isotactic polypropylene/polystyrene immiscible blends
No full textInternational audienceWe investigate the inter-phase migration of nucleating particles and their effect on the fractionated crystalli-zation of polypropylene droplets dispersed in an immiscible polystyrene matrix by preparing melt-mixed 90/10wt% PS/PP blends with selected nucleating agents. Different concentrations of nucleating agents (NAs): Phta-locianene Blue, NA11, Talc, and sodium benzoate, were initially incorporated either in neat PP or in neat PS.Then the different PS/PP/NAs blends were prepared. Contact angles were determined for the neat polymers andthe NAs, and the results indicated that, from a thermodynamics point of view, all NAs should remain or migrateto the PS phase. According to SEM observations, a sea-island morphology was obtained that did not vary with NAaddition. Hence the results should be independent of differences in the morphology.PP droplets crystallized in neat blends in three well-differentiated crystallization peaks (i.e., fractionatedcrystallization). The NAs induce a concentration-dependent increase in the high-temperature crystallization peakat the expense of reducing the low-temperature peaks, as droplets become in contact with or contain the NAs.When compared at a constant concentration in one of the phases, the nucleating agents have efficiencies thatdecrease in the order: Pht Blue ≈NA11>Talc>Sod Benz. Surprisingly, for the three most effective NAs, it wasfound that adding them initially to the PS phase led to a much higher nucleation efficiency (evaluated in terms ofincreases in peak crystallization temperature) than adding them to PP. This indicates that these NAs, initiallypresent in the PS phase, migrate to the interface or to the bulk of the PP phase (against thermodynamics). SodBenz was the only exception, as it shows a higher thermodynamic affinity to the PS phase. We explain themigration of most particles from the PS phase to the phases’ boundary or to the bulk of the PP droplets byconsidering that kinetic factors dominate the behavior, as, from a rheological perspective, the minor component(PP) always displays a lower viscosity than the matrix component (PS) under the chosen mixing conditions
Développement de mousses polymères par extrusion assistée par CO2 supercritique : assemblage d'âme pour panneaux sandwich aéronautiques et caractérisation des propriétés acoustiques
No full textInternational audienceLes structures sandwich sont très utilisées dans de nombreuses applications aéronautiques et spatiales grâce à leur rapport rigidité/masse favorable. Parmi les matériaux d’âme les plus utilisés, nous trouvons le nid d’abeille Nomex® et l’aluminium, à la fois très légers, résistants aux contraintes mécaniques et au feu. Cependant, ces structures sandwich classiques présentent des défauts importants tels qu’un faible taux d’amortissement et d’isolation acoustique [1], ainsi qu’une faible résistance à l’impact.Dans l’optique de développer de nouveaux matériaux d’âme pour contourner ces limitations des structures sandwich, une solution prometteuse consiste à utiliser des matériaux d’âme alvéolaires tels que les mousses polymères thermoplastiques. Cette famille de matériaux présente en effet plusieurs avantages, comme la facilité de mise en oeuvre, la capacité d’absorber l’énergie pendant un impact à faible énérgie (résilience), la recyclabilité et des propriétés accrues en termes d’isolation thermique et acoustique.Parmi les différentes technologies de moussage applicables aux polymères [2], la technique de moussage physique par extrusion assistée par CO2 supercritique [3] présente l’avantage d’avoir un impact environnemental très limité, ainsi qu’une microstructure et des propriétés qui peuvent être modifiées en fonction des paramètres procédé. Cette technologie reste cependant peu explorée dans le domaine des matériaux composites, notamment à cause de la difficulté de maîtriser la forme de la mousse à la sortie de la filière d’extrusion.Le projet ONOMATOPE, financé par l’IRT Saint-Exupéry et la fondation STAE, a permis de mener une première étude à ce propos, en explorant le potentiel d’utilisation de ces mousses dans le domaine aéronautique. Dans ce cadre, plusieurs mousses à base d’acide poly lactique (PLA) ont été développées avec différentes propriétés (densités, taille et densité de cellules, cristallinité). Les différents produits à l’état brut après extrusion ont été ensuite utilisés pour produire des panneaux en mousse assemblés, qui ont enfin été caractérisés avec un tube de Kundt pour accéder à leurs propriétés acoustiques
Preparation, characterisation and utilisation of biosourced nickel and iron-based catalysts for hydrogen production
No full textInternational audienceThe Paris Agreement (2015) engaged the 195 signatory nations to reduce greenhouse gas emissions. The valorization of biomass and biowaste into hydrogen and biofuels may play a significant role in reaching this objective, due to the carbon neutrality and high availability of these bioresources. The Water Gas Shift reaction (WGS), which allows enhancing the conversion of syngas into hydrogen, is involved in many thermochemical conversion processes such as gasification, Fisher-Tropsch Synthesis, and biogas reforming. It typically occurs between 180 and 400°C in the presence of noble or transition metal-based catalysts, including iron (Fe) and nickel (Ni) (Ghogia, 2021). Commercial catalysts present a high environmental impact and a high dependence on critical or precious metals (Said, 2017). To overcome this problem, catalysts may be produced from bioresources with a high metal content, which requires a deep knowledge on the complex and heterogeneous structure of bioresources and on metal catalytic activity. The objective of this work is to prepare, characterize and utilize biosourced catalysts from bioresources rich in catalytic elements for enhancing hydrogen production through WGS reaction.In a first approach, raw fern and willow were selected due to their ability to cumulate heavy metals from soil by phytoremediation. For catalysts preparation, a part of raw biomass was pyrolyzed under N2 from 25°C to 800°C at 2°C/min, followed by an isothermal step at 800°C for an hour. Impregnation was carried out by Wetness impregnation (WI) method for biomass samples and Incipient Wetness impregnation (IWI) for biochar samples, in both cases with an objective of 3 wt%biochar of Ni or Fe. Catalysts were then characterized in terms of organic element content (CHNS analysis), inorganic element content (ICP-AES) and its dispersion on the carbonaceous matrix (SEM, TEM), thermal stability (TGA-DSC), surface area (BET, N2), textural properties and surface chemical groups (TPD, TPR, XRD).Catalysts were then tested in WGS reaction. A fixed bed reactor (8 mm diameter, 25 cm long) was filled with 1.00±0.01 g of each biosourced catalyst and an inert bed of α-Al2O3 (Ghogia, 2021). Permanent gases were analyzed using an in-line µ-GC/TCD device. A first screening of the catalysts was carried out in Reverse WGS conditions (RWGS) to facilitate reactant introduction in gas phase, at 400°C, 3 bar and a ratio of reactants equal to 1:1 (CO2:H2). In a second step, the best catalysts were tested in WGS reaction conditions (220°C, 3 bar, 1:5.5 CO:H2O). Biosourced catalyst structure was compared before and after the chemical reaction.The produced biosourced catalysts showed their thermal stability in TGA up to 500°C. Concerning the impregnation method, WI required 2 to 4 times less time and up to 3 times less metal nitrate than IWI catalysts and therefore biomass impregnation was facilitated. This may be explained by the aromatic nature of biochar leading to formation of Van der Waals bonds between the metals introduced by impregnation and the carbonaceous structure (Said, 2017). In the case of biomass, metals make covalent bonds with biomass structure during impregnation, which results in a strong retention of metals by the carbonaceous structure after pyrolysis. Fern biochar IWI impregnated with Ni showed promising activity in RWGS with an initial CO2 conversion of 20% (~35% at equilibrium) and an average selectivity for CO compared to CH4 of 88%. Willow biochar WI impregnated with Fe catalysts lower CO2 conversion, but a higher selectivity to CO (>98%). Non impregnated fern and willow biochars showed lower CO2 conversion with no CH4 production. Future work will test the selected biosourced catalysts in WGS conditions, to identify the key parameters of the biosourced catalysts leading to the maximum syngas conversion rate, as well as H2 productivity and selectivity, as a function of WGS operating conditions
Un système d'aide à la décision basé sur un contrôleur de la chaîne logistique pour la gestion des risques
No full textWith the advancement of globalization, companies need to collaborate with other companies in order to meet the demands of the market on a global scale. Due to the need for more networking among companies and the increased risk of uncertainty in the supply chain, companies need better digital means for risk management. Although the concept of Supply Chain 4.0 provides a theoretical foundation for supply chain management, companies still lack effective means to share risks and exchange information with other enterprises.To address the above problem, we design a novel computer framework to deal with this challenge. We named this framework " A Decision Support System Based on Supply Chain Control Tower ". Technically, the framework integrates and visualizes various types of data in the supply chain and adopts the computer framework of decision support systems. Methodologically, the framework integrates two techniques, multi-criteria decision making and the concept of supply chain control tower.Contribution: This manuscript introduces a novel supply chain control tower based on a decision support system. The framework aims to support companies overcome information silos, improve supply chain information transparency, and utilize group decision support making to share common risks. In order to validate the effectiveness of the framework, we developed two computer simulation platforms. After more than 20 rounds of simulation, we found that 54% to 70% of the KPIs were substantially optimized if the framework was used, in the context of facing the same risk. Meanwhile, the construction of the two simulation platforms also provides a technical basis for future research on the control tower concept and an experimental platform for more computer algorithms to be integrated into supply chain research.Avec l'évolution de la mondialisation, les entreprises doivent collaborer entre elles afin de répondre aux demandes du marché à l'échelle mondiale. La mise en réseau entre les entreprises de plus en plus forte ainsi que le risque accru d'incertitude dans la chaîne d'approvisionnement, amènent les entreprises à améliorer leurs moyens numériques pour la gestion des risques. Bien que le concept de la chaîne d'approvisionnement 4.0 fournisse une base théorique pour la gestion de la chaîne d'approvisionnement, les entreprises manquent encore de moyens efficaces pour partager les risques et échanger des informations avec d'autres entreprises. Pour résoudre ce problème, nous avons conçu une nouvelle plateforme logicielle pour relever ce défi. Nous appelons cette plateforme "Système d'aide à la décision basé sur le contrôle de la chaîne d'approvisionnement". Techniquement, la plateforme intègre et visualise divers types de données dans la chaîne d'approvisionnement et s'inscrit dans la lignée des systèmes d'aide à la décision. Sur le plan méthodologique, la plateforme intègre deux techniques, la prise de décision multicritères ainsi que le concept de contrôle de la chaîne d'approvisionnement.Contribution : Ce manuscrit présente une nouvel outil de contrôle de la chaîne d'approvisionnement basée sur un système d'aide à la décision. La plateforme développée vise à aider les entreprises à surmonter les silos d'information, à améliorer la transparence des informations de la chaîne d'approvisionnement et à utiliser la prise de décision de groupe pour partager les risques communs. Afin de valider l'efficacité de la plateforme, nous avons développé deux approches de simulation informatique. Après plus de 20 cycles de simulation, nous avons constaté que 54 % à 70 % des indicateurs clés de performance étaient considérablement optimisés si le système d'aide à la décision ainsi que l'outil de contrôle sont utilisés, dans le contexte de risque identique. Parallèlement, la construction des deux plateformes de simulation fournit également une base technique pour de futures recherches sur le concept d'outil contrôle ainsi que sur la plateforme expérimentale pour laquelle l'intégration d'autres algorithmes d'aide à la décision est possible
Demand-supply alignment in supply chain networks with access to hyperconnected production options
No full textInternational audienceSupply chain networks today comprise of various decentralized actors, subject toconstantly evolving challenges and customer expectations, and operate in a volatile, uncertain, and disruption-prone environment. These challenges and complexities bring in informational and material flow distortions, making it hard to align demand and supply with agility. Building a centralized optimization model for such complex systems tends to be computationally expensive and unscalable for real-world application. With this motivation, we propose a novel, real-world applicable multi-agent-based approach for collaborative and agile demand-supply alignment, through dynamic prediction-driven planning and operational decision-making. We first demonstrate the applicability and configurability of our approach with a real-world supply chain network operating in a stochastic and disruptive environment, with the desired characteristics in congruence with the Physical Internet framework. We then demonstrate the simulation-testing capability of our approach by highlighting the potential benefits of leveraging a hyperconnected network of open certified production options