17 research outputs found
Composites en matiÚres premiÚres renouvelables et leurs procédés
National audienceThe development of new bio-based composites and efficient manufacturing methods that are suitable for series processing is the purpose of the current sub-project C4 of the Excellence Cluster MERGE, sponsored by DFG (Deutsche Forschungsgemeinschaft). Two different types of materials are combined: bio-based thermoplastic biopolymers such as bio-polyethylene (BioPE) or bio-polyamides (BioPA) and renewable reinforcing materials such as thin wood veneer or unidirectional flax fibers. To achieve a high-efficiency in terms of mass-production, reproducibility and flexibility, it is required to overlap several steps in the realization of semi-finished and final products. The improvement of the adhesion at the interface of the components, the implementation of continuous processes in order to increase energetically the yielding and the final design, through several methods, for the future potential applications are so many perspectives to achieve. MOTS-CLĂS : polymĂšre bio-basĂ© thermoplastique; renforcement naturel (Lin ou placage en bois) ; AmĂ©lioration de l'adhĂ©sion Ă l'interface matrice/renforcement ; ProcĂ©dĂ©s plastic/textile continu ; Application dans l'automobile et Ă©quipement sportifsLe dĂ©veloppement de matĂ©riaux bio-basĂ©s et de mĂ©thodes efficaces de mise en forme, adaptable Ă la production en sĂ©rie, est le but de l'actuel sous-projet C4 du programme d'excellence MERGE financĂ© par la DFG (Deutsche Forschungsgemeinschaft). Ainsi, deux types de matĂ©riaux sont combinĂ©s : Des polymĂšres bio-ressourcĂ©s thermoplastiques tels que bio-polyĂ©thylĂšne (BioPE) ou bio-polyamide (BioPA) et des matĂ©riaux de renforcements renouvelables tels que le placage en bois ou des fibres de lin unidirectionnelles continues. Pour atteindre un haut rendement en termes de production en masse, de reproductibilitĂ© et de flexibilitĂ©, il est requis de suivre plusieurs Ă©tapes dans la rĂ©alisation de produits semi-finis et finis. L'amĂ©lioration de l'adhĂ©sion Ă l'interface des composantes, la mise en place de procĂ©dĂ©s continus afin d'augmenter leur rendement, et la mise en forme finale, par diverses mĂ©thodes, pour des futures potentiels applications sont autant d'objectifs Ă atteindre
25th annual computational neuroscience meeting: CNS-2016
The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong
25th Annual Computational Neuroscience Meeting: CNS-2016
Abstracts of the 25th Annual Computational Neuroscience
Meeting: CNS-2016
Seogwipo City, Jeju-do, South Korea. 2â7 July 201
Technologieentwicklung zur Herstellung von naturfaserverstÀrkten Bauteilen in Leichtbauweise unter Einsatz von Ganzpflanzenrohstoffen
Die Verwendung von âklassischenâ Naturfasern als VerstĂ€rkungskomponente in Kunststoffbauteilen ist durch ihr besonderes Eigenschaftsspektrum in Kombination mit wirtschaftlichen und ökologischen Vorteilen im gesamten Lebenszyklus begrĂŒndet. Die Technologien zur Verarbeitung von Naturfasern zu Bauteilen wurden in den vergangenen Jahren kontinuierlich weiterentwickelt, wobei das Hauptaugenmerk auf der Optimierung von Material- und Verfahrensparametern bekannter Technologielösungen lag. Komplexe Anwendungen im Automobilbau erfordern allerdings eine ganzheitliche Betrachtung der gesamten Wertschöpfungskette von der Rohstoffbereitstellung ĂŒber die Halbzeugfertigung bis hin zur Bauteilentwicklung und -herstellung. In diesem Zusammenhang weisen neuartige FaserverstĂ€rkungen aus Ganzpflanzenrohstoffen (GPR) gegenĂŒber den konventionell aufgeschlossenen Naturfasern ein Potenzial fĂŒr deutlich höhere Material- und Kosteneffizienz auf. Ziel dieser Arbeit ist die Bereitstellung einer werkstoffgerechten Auslegungsstrategie fĂŒr eine neue durchgĂ€ngige Prozesskette zur Herstellung von naturfaserverstĂ€rkten Bauteilen unter Einsatz von Ganzpflanzenrohstoffen. Am Beispiel der Flachspflanze werden dabei die verketteten Prozessstufen und die zugehörigen Schnittstellen entwickelt, charakterisiert und validiert. DarĂŒber hinaus wird zur Umsetzung von Leichtbauanforderungen der Ansatz verfolgt, funktionale ZusammenhĂ€nge zwischen mechanischen Werkstoffkennwerten und lokaler Bauteildichte fĂŒr eine belastungsgerechte Bauteilauslegung in Leichtbauweise zu erfassen.The use of âclassicalâ natural fibres as reinforcing part for plastic components is caused by their particular property range in combination with economical and ecological advantages in the total life cycle. In recent years, technologies for the processing of natural fibres to components were continuously developed, focused on optimising material and process parameters of existing technology solutions. Certainly, complex applications in the automobile industry require an integrated consideration of the total value added chain from material supply to manufacturing of semi-finished products up to component development and production. In this regard novel fibre reinforcements made from whole plant materials possess potential for considerably higher material and cost efficiency compared to conventional natural fibres. The Intention of this work is to provide a material-specific dimensioning strategy for a new integrated process chain to produce natural fibre reinforced components by using raw materials made of the whole plant. Linked process steps and related interfaces were developed, characterised and validated by using the example of a flax plant. Moreover, the approach of realizing lightweight construction requirements is necessary in order to measure functional relations between material parameters and local density for the load-bearing part dimensioning in lightweight structure
Investigation of bio-based polyamide with short fibers for lightweight structures
In the automotive industry, petrochemical plastics are widespread because glass and carbon fiber-reinforced composites consist exclusively of petroleum-based matrix materials. So far, bio-based plastics couldnât meet the requirement profile due to their high prices, their inappropriate features and the ineligible quality assurance of their synthesis. But the development of new bio-based polyamides opens the opportunity to replace petroleum-based plastics and may initiate the use of bio-based plastic matrices for fiber-reinforced composites for automotive applications.In this study, short fiber-reinforced polyamide 10.10 composites were investigated. Short carbon and glass fibers were used in varying compositions along with different modifiers to optimize the resulting characteristics. Fiber breakage during twin screw extrusion processing was researched and affected by the use of lubricants. The effect of using lubricants was noticed after extrusion. The addition of lubricants caused negative effects on mechanical properties at concentrations higher than 0.5 % wt. Further influences on fiber matrix interactions were investigated by varying the parameters of injection molding and positive effects on tensile properties were recognized. Strengthening effects on resulting composites are discussed in terms of lightweight structure and cost-efficiency