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Sin-le-Noble, France

Cosson B.,Mines Douai
Key Engineering Materials | Year: 2015

Thermoplastic composites for structural applications are under growing development from the aerospace (carbon fibers with PEI, PPS or PEEK matrices mainly) to the automotive industry (glass and carbon fibers with PP, PA). The plastic deformation they can provide and the assembly facilities through welding techniques are well appreciated. Among the available welding technics, laser offers the possibility to assemble materials in a precise and localized manner and can be easily automated. However, due to the presence of continuous fibers at a high fiber volume fraction, propagation of the laser energy through the composite that present local variation of fiber volume fraction is not as straight forward as in a homogeneous material. Modelling of the laser welding of a thermoplastic/continuous glass fiber is considered here. The study takes into account the microstructure of the composite in order to evaluate changes in local energy absorption and diffusion directly linked with the thickness. Modelling of the welding process is developed from the representation of the moving laser beam. The beam propagation through the composite thickness is considered thanks to the ray tracing method. The proposed method is able to optimise the welding process in function of the microstructure and the material properties of the welded parts. © (2015) Trans Tech Publications, Switzerland. Source

Thiery V.,Mines Douai
Microscopy and Microanalysis | Year: 2014

Mimetite, Pb5(AsO4)3Cl, is a ubiquitous mineral that is of interest in various fields such as ore mineralogy, environmental studies, and minerals engineering. Mimetite generally forms hexagonal prisms and barrel-shaped crystals, but its fibrous form is quite an uncommon one. Here we attempt to present its worldwide occurrences on the basis of a literature review. We then present a study on fibrous mimetite from one of its historical locations based on the petrographic microscope, SEM-SE and EDX, and Raman spectroscopy. © Microscopy Society of America 2014. Source

Comas-Cardona S.,CNRS Research Institute in Civil Engineering and Mechanics | Cosson B.,Mines Douai | Bickerton S.,University of Auckland | Binetruy C.,CNRS Research Institute in Civil Engineering and Mechanics
Composites Part A: Applied Science and Manufacturing | Year: 2014

Structural composite manufacturing relying on Liquid Composite Molding technologies is strongly affected by local variability of the fibrous reinforcement. Optical techniques using light transmission are used and allow field measurements of areal weight (and fibre volume fraction) of glass fibre reinforcement. The coupling of obtained areal weight mappings along with injection flow fronts is used to extract in-plane permeability fields. The current work presents results with a focus on glass random mats, but the method can be adapted to any glass fibrous medium. A study of convergence and error due to discretization is performed. Also the influence of the stacking of fibrous layers on the preform variability is analyzed. The major advantage of the proposed technique is a relatively fast acquisition of statistical data on reinforcement variability, which can be later utilized in stochastic based process simulations. © 2013 Elsevier Ltd. All rights reserved. Source

Douville M.-A.,Mines Douai | Douville M.-A.,University Claude Bernard Lyon 1 | Le Grognec P.,Mines Douai
International Journal of Solids and Structures | Year: 2013

Sandwich structures are widely used in many industrial applications, due to the attractive combination of a lightweight and strong mechanical properties. This compromise is realized thanks to the presence of different parts in the composite material, namely the skins and possibly core reinforcements or thin-walled core structure which are both thin/slender and stiff relative to the other parts, namely the homogeneous core material, if any. The buckling phenomenon thus becomes mainly responsible for the final collapse of such sandwiches. In this paper, classical sandwich beam-columns (with homogeneous core materials) are considered and elastic buckling analyses are performed in order to derive the critical values and the associated bifurcation modes under various loadings (compression and pure bending). The two faces are represented by Euler-Bernoulli beams, whereas the core material is considered as a 2D continuous solid. A set of partial differential equations is first obtained from a general bifurcation analysis, using the above assumptions. Original closed-form analytical solutions of the critical loading and mode of a sandwich beam-column are then derived for various loading conditions. Finally, the proposed analytical formulae are validated using 2D linearized buckling finite element computations, and parametric analyses are performed. © 2013 Elsevier Ltd. All rights reserved. Source

Traore M.,Lille University of Science and Technology | Chammas A.,Mines Douai | Duviella E.,Mines Douai
Reliability Engineering and System Safety | Year: 2015

In this paper, we are concerned by the improvement of the safety, availability and reliability of dynamical systems' components subjected to slow degradations (slow drifts). We propose an architecture for efficient Predictive Maintenance (PM) according to the real time estimate of the future state of the components. The architecture is built on supervision and prognosis tools. The prognosis method is based on an appropriated supervision technique that consists in drift tracking of the dynamical systems using AUDyC (AUto-adaptive and Dynamical Clustering), that is an auto-adaptive dynamical classifier. Thus, due to the complexity and the dynamical of the considered systems, the Failure Mode Effect and Criticity Analysis (FMECA) is used to identify the key components of the systems. A component is defined as an element of the system that can be impacted by only one failure. A failure of a key component causes a long downtime of the system. From the FMECA, a Fault Tree Analysis (FTA) of the system are built to determine the propagation laws of a failure on the system by using a deductive method. The proposed architecture is implemented for the PM of a thermoregulator. The application on this real system highlights the interests and the performances of the proposed architecture. © 2014 Elsevier Ltd. All rights reserved. Source

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