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Thuault A.,CRISMAT | Eve S.,CRISMAT | Bazin J.,CRISMAT | Charlet K.,IFMA | And 3 more authors.
Materiaux et Techniques | Year: 2011

In this paper we seeked for correlation among the biocomposition, morphological parameters and mechanical properties of flaw fibre. Seven varieties among the most frequently cultivated in Normandy are examined. Biocomposition analyses have shown no significant differences between the different varieties while noticeable differences have been evidenced between the varieties for mechanical properties, and these are comparable to the dispersion within a given variety. Thus, the differences in mechanical properties among these varieties are not ascribed to morphological or biocomposition parameters. © 2011 EDP Sciences.

Thuault A.,CRISMAT | Bazin J.,CNRT Materiaux | Eve S.,CRISMAT | Breard J.,LOMC | Gomina M.,CRISMAT
Journal of Industrial Textiles | Year: 2014

This paper presents the results of a numerical simulation of the ultimate flax fibre (Linum usitatissimum) tensile mechanical behaviour using finite element analysis. Experimental data were used to develop a numerical multilayer model of the flax fibre. Thus, the influence of some parameters, such as cell wall thicknesses, microfibrils angles (MFAs), biochemical composition and mechanical properties of the biochemical components, on the flax fibre tensile mechanical behaviour has been investigated. Results show that the typical stress-strain curve profile of the flax fibre could be due to the mechanical properties of hydrophilic components (hemicelluloses) and thus to the environmental conditions. A parameter sensitivity study reveals that ultrastructural parameters (hemicelluloses and cellulose Young's modulus) strongly influence the flax fibre mechanical behaviour and structural parameters (S2 cell wall layer MFA and thickness) significantly influence the fibre longitudinal Young's modulus. Thus, the knowledge of the fibre ultrastructure seems to be the key of the understanding of the flax fibre mechanical behaviour. © The Author(s) 2013.

Jorel C.,National Engineering School of Caen | Colder H.,CRISMAT | Galdi A.,National Engineering School of Caen | Galdi A.,CNR Institute of Neuroscience | And 2 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2012

We report the growth of epitaxial Pb(Zr0.54Ti0.46)O3 (PZT) thin films on yttria-stabilized zirconia buffered silicon substrates by pulsed laser deposition. We demonstrate a full in plane epitaxy of the buffer layer, showing a RMS roughness of less than 0.3 nm for a 120 nm thick layer. This buffer layer allows the growth of fully (110) textured oxide conducting SrRuO3 and subsequent functional oxide layers. Here the Pb(Zr,Ti)O3 oxide was chosen to demonstrate its possible integration in piezoelectric microelectromechanical systems on silicon. © Published under licence by IOP Publishing Ltd.

Prou N.,Crismat | Riviere F.,Crismat | Berland C.,University Paris Est Creteil
Conference Proceedings - 9th Conference on Ph. D. Research in Microelectronics and Electronics, PRIME 2013 | Year: 2013

The LInear amplification with Nonlinear Component transmitter is a high power efficient architecture for radio communication systems. Nevertheless, this architecture is sensitive to mismatches between the two paths and its efficiency performances are dependent on the power amplification stage topology. Additively, careful attention has to be paid to baseband performances in terms of sampling rate, Digital to Analog Converters (DACs) resolution, reconstruction filter bandwidth. In this paper, we present the specification of the reconstruction filters for a single carrier WCDMA 3GPP base station transmitter and this, according to the Power Amplifier (PA) class (switched mode (SMPA) or AB class). We address the impact of the class of the PAs on the overall performances and on the reconstruction filters specifications. Admissible time delays and gain mismatches between the two paths will also be quantified. © 2013 IEEE.

Hervas I.,CRISMAT | Bettaieb M.B.,National Engineering School of Caen | Thuault A.,CRISMAT | Hug E.,CRISMAT
Materials and Design | Year: 2013

Compression tests were carried out on ductile cast iron with different sample geometries in order to understand the influence of the stress triaxiality on the local strain. The tests were performed in dry friction conditions involving a complex local stress and strain state with a severe barrelling. The numerical simulation of the compression tests was achieved by using finite element analysis. Local strain was evaluated using microstructural quantifications. A relationship between the nodule strain, experimentally determined at different stress-strain stages, and the numerical simulation is proposed. The numerical predictions agree with the distribution of the experimental aspect ratio defined as the ratio between the major and minor axis of the graphite nodules. This study shows that the nodule strain is a good indicator of the total material strain at room temperature for different triaxiality states and complex strains. In addition, it was highlighted that graphite nodules cannot always be considered as ordinary voids during the plastic strain process. © 2013 Elsevier Ltd.

Thuault A.,CRISMAT | Domenges B.,Presto Engineering | Hervas I.,CRISMAT | Hervas I.,Arts et Metiers ParisTech | Gomina M.,CRISMAT
Cellulose | Year: 2015

The development of the use of flax fibre as reinforcement of eco-friendly composite materials requires a good knowledge of its hydrothermal and mechanical behaviours. To this end the fibre internal structure must be finely investigated. Transmission electron microscopy was used to analyse the morphology of the fibre cell walls in terms of the arrangement of the layers and their thickness. Thus, an alternative eco-friendly staining method, based on oolong tea extract was successfully implemented. The results reveal an arrangement at the nanoscale slightly different from the classical four layer model encountered in the literature: the inner layer includes three to four sub-layers. The cell walls comprises two outer layers of relative thickness of about 10 %, a middle layer of about 70 % and a group of thinner layers (called sub-layers) that are contiguous to the lumen with relative thickness of about 20 %. © 2015, Springer Science+Business Media Dordrecht.

Beloufa A.,CRISMAT
Journal of Heat Transfer | Year: 2012

Automotive connectors in modern car generations are submitted to high current; this can cause many problems and requires the minimization of their electrical contact resistances. The new major contribution of this work is the optimization by finite element method of contact resistance, contact temperature, design, and mechanical stress of sphere/plane contact samples. These contact samples were made with recent high-copper alloys and were subjected to indentation loading. Experimental tests were carried out in order to validate the developed numerical model and to select the material which presents a low contact temperature and contact resistance. Another model with multipoint contacts was developed in order to minimize electrical contact resistance and contact temperature. Shape optimization results indicate that the volume of contact samples was reduced by 12. The results show also for the model with multipoint contacts that the contact resistance was reduced by 41, contact temperature by 22 and maximum Von Mises stress by 49. These several gains are more interesting for the connector designers. © 2012 American Society of Mechanical Engineers.

Quetel-Weben S.,CRISMAT | Retoux R.,CRISMAT | Noudem J.G.,CRISMAT
Journal of the European Ceramic Society | Year: 2013

n-Type Ca0.9Yb0.1MnO3-δ thermoelectric (TE) powders were prepared by solid state synthesis (SSS) and co-precipitation method (Cop). The bulk TE materials were consolidated using conventional sintering (CS) and spark plasma sintering (SPS) respectively. The shrinkage behavior, as well as the sample densification strongly depends on the starting particle size. Consequently, the bulk samples from normal powder (SSS) and nano-powder (Cop) were prepared with similar density by using different sintering temperatures, of 1400°C and 1200°C, then 1200 and 950°C for CS and SPS respectively. Such a decrease (up to 200°C) of the sintering temperature is a consequent progress in terms of engineering for applications. Another advantage of the co-precipitation process compared to the conventional solid state synthesis is that, due to the small particle sizes and the decreased sintering temperature, grain growth was limited and TE properties were enhanced. The interest of the SPS process was also evidenced and we are presenting here the structural and microstructural investigations. In addition, the thermoelectric properties of samples prepared with two different processes were studied with the figure of merit of 0.18 at 750°C. © 2013 Elsevier Ltd.

David R.,University of Lille Nord de France | Kabbour H.,University of Lille Nord de France | Bordet P.,CNRS Neel Institute | Pelloquin D.,CRISMAT | And 3 more authors.
Journal of Materials Chemistry C | Year: 2014

The series of modular compounds [BanCo2+nO3n+2][BaCo6O9] (n = 1 to 3) including experimental and hypothetical terms, was investigated using DFT calculations and several experimental results. A systematic evolution of the electronic and magnetic states was evidenced along the series leading to ordered CoII/CoIIIversus mixed CoIII/IV charge segregation in two distinct structural motifs. In essence, using different packing modes within the labile [BanCo2+nO3n+2] block, we have systematized the spin state dependence on the CoO6 connectivity, i.e. corner-sharing (HS states) against face-sharing (LS states). We also show that the electronic and magnetic features of the [BaCo6O9] blocks do not vary trough the series, (i.e. HS-CoII and LS-CoIII charge ordering) whereas the [BanCo2+nO3n+2] blocks hold drastic changes from n = 1 to 3. In particular, the later carries a mixed iii/iv cobalt charge for n ≥ 2. It leads to a triple valence cobalt state. For n = 2, we experimentally observe at 4 K a superstructure (2a, 2c) superstructure accompanied by a perfect CoII/CoIII/CoIV charge ordering. The charge ordering occurs at Tt = 160 K and is accompanied by a transition in the electronic transport leading to a 2D-VRH behaviour below Tt. This journal is © the Partner Organisations 2014.

Coq Germanicus R.,CRISMAT | Eve S.,CRISMAT | Lallemand F.,IPDIA Inc | Hug E.,CRISMAT
Materiaux et Techniques | Year: 2015

In order to protect microelectronic structures, a silicon nitride (Si3N4) film is typically used as the final passivation layer. During the Back End process, wafer processing steps such as thinning, bonding, sawing or assembly could induce several mechanical strains in the materials. In this paper, the mechanical behavior of Si3N4 deposited on two under layers: SiO2 and Al98.96Si1.00Cu0.04, from the same silicon wafer, is investigated by nanoindentation. The load-displacement curves indicate different mechanical behaviors. The unloading curve shows mainly viscoelastic deformation for the Si3N4/SiO2 system. Deposited on AlSiCu, the sample exhibits a plastic deformation with pop in, when the indenter penetrates into the material. Residual indents measured with an atomic force microscope, after nanoindentation, present significant shape differences, for the under layer AlSiCu the indentation induces cracks. © 2015 EDP Sciences.

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