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Esch - sur - Alzette, Luxembourg

Polyelectrolyte multilayer (PEM) films present a versatile surface functionalization method allowing to address many applications. These coatings suffer; however, from weak mechanical properties this problem can be addressed by the regular incorporation of clays in the layering process. To allow for an even better control of a whole set of film properties, among them their thermal stability, their stability in water, and their impermeability to anions, we postmodify (PAH-MMT)(n) films with polydopamine, by putting the pristine PEM films in contact with an oxygenated dopamine solution. This straightforward treatment allows to totally suppress the diffusion of hexacyanoferrate anions in the films and affects significantly its mechanical properties even, if the distribution of polydopamine through the film thickness is not yet known. Source


This article describes the implementation of a finite strain viscous hyper-elastic material law into a finite element code. The material model is made up of a Maxwell element in parallel with a spring. Both springs represent hyper-elastic material behaviour, and compressibility is taken into account. In addition to that, the sensitivity analysis using direct differentiation is described extensively. The implementation is verified by three test cases, uniaxial tension, pure shear and indentation testing. The sensitivity analysis by direct differentiation is validated by comparison against results obtained by a finite difference scheme. © 2010 Elsevier Ltd. All rights reserved. Source


Lallemand C.,CRP Henri Tudor
Proceedings of the 2011 SIGCHI Symposium on Engineering Interactive Computing Systems, EICS 2011 | Year: 2011

Even though the benefits of usability have widely been proven, it seems that development-oriented companies face many difficulties to introduce usability practices into their defined development processes. This paper describes the overall methodology deployed as an attempt to achieve a closer integration of usability practices in the software development process. Model-Driven Engineering (MDE) is used as a basis for this integration. Providing a precise framework composed of models and transformations, it allows to track usability problems and to highlight where exactly they occur in the development process. We will thus be able to link every step of the process to specific ergonomic inputs and to study their consequences on the usability of the generated system. Because MDE will only be used as a way among others to investigate some hypotheses on usability and User-Centered Design (UCD) in general, our results are expected to provide valuable and generic information on usability and UCD processes. Copyright 2011 ACM. Source


Poncot M.,CNRS Jean Lamour Institute | Addiego F.,CRP Henri Tudor | Dahoun A.,CNRS Jean Lamour Institute
International Journal of Plasticity | Year: 2013

A model enabling the determination of the intrinsic mechanical constitutive equations of uniaxially stretched polymers is presented. This model takes into account the cavitation-induced volume strain which can occur during the deformation of such materials. In particular, the true intrinsic axial stress and strain depends on the overall volume strain and a form factor depicting the evolution of the voids shape. Based on our model, the true intrinsic behaviour of high-density polyethylene (HDPE), polypropylene/ethylene-propylene rubber (PP/EPR), and polyethylene terephtalate (PET) was assessed in tension. Compared to the overall true behaviour, the intrinsic true behaviour of the materials did not exhibit anomalies at large strain levels with changing experimental parameters (strain rate and temperature), and can be accurately predicted by means of phenomenological constitutive equations as the one proposed by G'sell and Jonas (1979). © 2012 Elsevier Ltd. All rights reserved. Source


Deraemaeker A.,Roosevelt University | Nasser H.,CRP Henri Tudor
International Journal of Solids and Structures | Year: 2010

This paper focuses on the evaluation of the homogeneous properties of the active layer in Macro Fiber Composite (MFC) transducers using finite element periodic homogenization. The proposed method is applied to both d31 and d33-MFCs and the results are compared to previously published analytical mixing rules, showing a good agreement. The main advantages of the finite element homogenization is the possibility to take into account local details in the representative volume element such as complicated electrode patterns or local variations of the poling direction due to curved electric field lines. Although these influences have been found to be rather small in the present study, the method presented is useful for a better understanding of the behavior of piezocomposite transducers. © 2010 Elsevier Ltd. All rights reserved. Source

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