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Search Results: 1 - 10 of 8317 matches for " Fran?ois Trochu "
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Experimental Characterization by Fluorescence of Capillary Flows in the Fiber Tows of Engineering Fabrics  [PDF]
Franois LeBel, Amir Ershad Fanaei, édu Ruiz, Franois Trochu
Open Journal of Inorganic Non-metallic Materials (OJINM) , 2012, DOI: 10.4236/ojinm.2012.23004
Abstract: Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or covering of reinforcement with a plastic bag, a polymer resin is either injected or infused under vacuum through the fiber bed. The engineering fabrics commonly used in LCM possess generally dual scale architecture in terms of porosity: microscopic pores exist between the filaments in the fiber tows, while macroscopic pores appear between the tows as a result of the stitching/weaving fabrication process. On a microscopic scale, capillary flows in fiber tows play a major role on the quality of composites made by resin injection through fibrous reinforcements. In order to better understand the mechanisms that govern the impregnation of fibrous reinforcements in LCM, a study of wicking behavior is carried out in fiber tows. The experimental approach is based on capillary rise experiments, which are less expensive and time-consuming than other more standard characterization techniques often used in porous media. In addition, it allows gathering representative data on the wicking properties of fiber tows as a function of their morphological characteristics such as micro-porosity, total cross-section area, specific surface area, filament diameter and packing configuration. The morphological properties of the fiber tows will also be characterized by other standard experimental methods in order to compare with the results obtained by capillary rise experiments. These standard methods include gravimetry for the micro-porosity and fiber mass density, microscopic analysis to measure the filament diameter, cross-section area and packing configuration of the filaments and capillary flow porometry to evaluate the equivalent pore diameter. The capillary rise method has already been used not only in Soil Mechanics, but also to characterize engineering textiles used in high performance composites. Such experiments are not easy to perform, because of technical difficulties such as textile geometrical alteration during testing, changes in fluid properties due to solvent evaporation and inaccurate observation of the progression of the capillary front (fading). To circumvent these problems, a monitoring technique based on fluorescent dye penetration inspection (DPI) and CCD image acquisition is proposed in this investigation. Visual monitoring of the capillary front is coupled with real-time fluid mass acquisition using a high resolution balance. Experimental
Measurement of the In-Plane Thermal Conductivity of Long Fiber Composites by Inverse Analysis  [PDF]
Bassam Assaf, Vincent Sobotka, Franois Trochu
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.72005
Abstract: In the present work, inverse thermal analysis of heat conduction is carried out to estimate the in-plane thermal conductivity of composites. Numerical simulations were performed to determine the optimal configuration of the heating system to ensure a unidirectional heat transfer in the composite sample. Composite plates made of unsaturated polyester resin and unidirectional glass fibers were fabricated by injection to validate the methodology. A heating and cooling cycle is applied at the bottom and top surfaces of the sample. The thermal conductivity can be deduced from transient temperature measurements given by thermocouples positioned at three chosen locations along the fibers direction. The inverse analysis algorithm is initiated by solving the direct problem defined by the one-dimensional transient heat conduction equation using a first estimate of thermal conductivity. The integral in time of the square distance between the measured and predicted values is the criterion minimized in the inverse analysis algorithm. Finally, the evolution of the in-plane composite thermal conductivity can be deduced from the experimental results by the rule of mixture.
A Comparative Study of Dispersion Techniques for Nanocomposite Made with Nanoclays and an Unsaturated Polyester Resin
Farida Bensadoun,Nadir Kchit,Catherine Billotte,Franois Trochu,Edu Ruiz
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/406087
Abstract: Over the last few years, polymer/clay nanocomposites have been an area of intensive research due to their capacity to improve the properties of the polymer resin. These nanocharged polymers exhibit a complex rheological behavior due to their dispersed structure in the matrix. Thus, to gain fundamental understanding of nanocomposite dispersion, characterization of their internal structure and their rheological behavior is crucial. Such understanding is also key to determine the manufacturing conditions to produce these nanomaterials by liquid composite molding (LCM) process. This paper investigates the mix of nanoclays particles in an unsaturated polyester resin using three different dispersion techniques: manual mixing, sonication, and high shear mixing (HSM). This paper shows that the mixing method has a significant effect on the sample morphology. Rheology, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) characterization techniques were used to analyze the blends morphology and evaluate the nanoclays stacks/polymer matrix interaction. Several phenomena, such as shear thinning and premature polymer gelification, were notably observed. 1. Introduction Recent advances in the composite materials field are related to the addition of nanoparticles such as carbon nanotubes or nanoclays to improve thermal, mechanical, or electrical properties. Nanoparticle additives, like nanoclays, are widely used in various industries such as cable coatings, adhesives, inks, pharmaceuticals and automotives [1, 2]. One of the most common nanoclay forms is MMT layered silicate with a particle thickness of 1?nm and 70 to 100?nm crosswise silica platelets [3]. The choice of montmorillonite nanoparticles in previous researches is mainly due to the fact that they are commonly available in nature and inexpensive. A minimal content of such additives between 1 to 6%?wt can improve the properties of the polymer matrix by increasing flexural modulus by up to 31% and lowering the coefficient of linear thermal expansion by 66% [1, 4, 5]. However, the incorporation of nanoparticles into the liquid matrix is still a challenge, because it requires proper dispersion and exfoliation. Nanoclays are widely used in thermoplastic matrices, but only few studies report to their addition in polyester thermoset resins. This explains the lack of results on the thermal and mechanical properties and especially on the rheology of the mix. Rheology is a widely used evaluation method for detecting the presence of interconnected structures. This technique seems to be
A Study of Nanoclay Reinforcement of Biocomposites Made by Liquid Composite Molding
Farida Bensadoun,Nadir Kchit,Catherine Billotte,Simon Bickerton,Franois Trochu,Edu Ruiz
International Journal of Polymer Science , 2011, DOI: 10.1155/2011/964193
Abstract: Liquid composite molding (LCM) processes are widely used to manufacture composite parts for the automotive industry. An appropriate selection of the materials and proper optimization of the manufacturing parameters are keys to produce parts with improved mechanical properties. This paper reports on a study of biobased composites reinforced with nanoclay particles. A soy-based unsaturated polyester resin was used as synthetic matrix, and glass and flax fiber fabrics were used as reinforcement. This paper aims to improve mechanical and flammability properties of reinforced composites by introducing nanoclay particles in the unsaturated polyester resin. Four different mixing techniques were investigated to improve the dispersion of nanoclay particles in the bioresin in order to obtain intercalated or exfoliated structures. An experimental study was carried out to define the adequate parameter combinations between vacuum pressure, filling time, and resin viscosity. Two manufacturing methods were investigated and compared: RTM and SCRIMP. Mechanical properties, such as flexural modulus and ultimate strength, were evaluated and compared for conventional glass fiber composites (GFC) and flax fiber biocomposites (GFBiores-C). Finally, smoke density analysis was performed to demonstrate the effects and advantages of using an environment-friendly resin combined with nanoclay particles. 1. Introduction Recent advances in the composites field are related to the addition of nanoparticles such as carbon nanotubes, nanoclays, or silicates nanoparticles to improve the thermal, mechanical, and electrical properties. Nanoparticle additives, like nanoclay, are widely used in various industries such as cable coatings, adhesives, inks, pharmaceutical and automotive [1, 2]. One of the most common nanoclay forms is montmorillonite (MMT) with a particle thickness of 1?nm and 70 to 100?nm crosswise silica platelets [3, 4]. The choice and extensive use of montmorillonite nanoparticles in previous research is mainly due to the fact that they are commonly available and inexpensive [5]. Minimal content (1–5%?wt) of such additives can improve the reinforcement of the polymer matrix by increasing flexural modulus by up to 31% and lowering the coefficient of linear thermal expansion [6–8]. However, the incorporation of nanoparticles into the liquid matrix is still a challenge, because it requires proper dispersion and exfoliation of the nanoclay. Since they are hydrophilic in their natural state and unevenly distributed, they must be organically modified to avoid agglomeration between
When neurological symptoms hides a nephrologic pathology and a cardiac abnormality  [PDF]
Clotilde Muller, Bernadette Faller, Franois Sellal, Franois Chantrel
Open Journal of Internal Medicine (OJIM) , 2011, DOI: 10.4236/ojim.2011.11002
Abstract: We bring report the case of a young woman who presents with neurological symptoms, and to which the practised investigations led to the discovery in chain of unexpected pathologies. These neurological disorders were revealing of the picture associating a nephrotic syndrome and a patent foramen ovale. This foramen was the major route of a rain of emboles ring peripheral favored by the nephrotic syndrome towards the cerebral hemispheres.
Labeled HepasphereTM behavior during venous drainage simulation at 1.5T  [PDF]
Hassan Jassar, Franois Langevin
Journal of Biomedical Science and Engineering (JBiSE) , 2010, DOI: 10.4236/jbise.2010.311142
Abstract: Stability of the magnetic resonance (MR) contrast agent inside vascular occlusion agents is important for their localization with magnetic resonance imaging (MRI). The aim of this paper is to study the behaviour of the superparamagnetic iron oxide (SPIO) within Hepaspheres? microparticles (MP) by MRI when they are submitted to negative pressure induced by venous drainage of a tumor. Therefore, a venous drainage model was established and three parameters were taken into account according to physiologic parameters in tumors: pH, temperature and flow blood rate. Four cycles of pumping were performed with the presence of labeled Hepaspheres? with Endorem®. Several MR images of MP and perfusion liquid were taken before and after pumping. Endorem® release was determined after correction of non-uniformity intensities in MR images. Intensity variation according to spatial position, coil and MR acquisition parameters was studied. Labeled microparticles (LB*MP) appeared as black spots in MRI images whatever duration and pH. Our model demonstrates the stability of the SPIO inside the occlusion agent during time. Moreover, the proposed correction method proves the reduction of the intensity non-uniformity in MRI images.
Architectural Model of a Biological Retina Using Cellular Automata  [PDF]
Franois Devillard, Bernard Heit
Journal of Computer and Communications (JCC) , 2014, DOI: 10.4236/jcc.2014.214008
Abstract: Developments in neurophysiology focusing on foveal vision have characterized more and more precisely the spatiotemporal processing that is well adapted to the regularization of the visual information within the retina. The works described in this article focus on a simplified architectural model based on features and mechanisms of adaptation in the retina. Similarly to the biological retina, which transforms luminance information into a series of encoded representations of image characteristics transmitted to the brain, our structural model allows us to reveal more information in the scene. Our modeling of the different functional pathways permits the mapping of important complementary information types at abstract levels of image analysis, and thereby allows a better exploitation of visual clues. Our model is based on a distributed cellular automata network and simulates the retinal processing of stimuli that are stationary or in motion. Thanks to its capacity for dynamic adaptation, our model can adapt itself to different scenes (e.g., bright and dim, stationary and moving, etc.) and can parallelize those processing steps that can be supported by parallel calculators.
Ethical Decision-Making in Clinical Nutritional Practice  [PDF]
Franois P. R. de Villiers
Food and Nutrition Sciences (FNS) , 2011, DOI: 10.4236/fns.2011.26089
Abstract: Ethics requires a critical evaluation of assumptions and arguments about norms and values; what should be done and what should not. Practitioners should practice ethically, and the professions should be at the forefront of applied ethics. There are four principles, patient autonomy, beneficence, non-maleficence and justice, which are guides to ethical day-to-day practice. Patient autonomy: Autonomy means self-rule by persons of their thoughts and actions. Patient autonomy requires the practitioner to realise that patients have the right to be involved in decision-making on their own behalf. Beneficence refers to the duty of the practitioner to do the best for the patient. The benefits of breast-feeding are many, and the eventual outcome on health enormous. Nevertheless, health-care workers are diffident in promoting breast-feeding, and readily accept excuses for not breast-feeding, contrary to the principle of beneficence. Non-maleficence refers to the duty of the practitioner not to do harm; it requires the practitioner to withhold harmful therapies; Vitamin E, for example, has been proven to be ineffective as an antioxidant in humans, and large doses have been proven to increase mortality. Yet these are the doses available in supermarkets and “Health shops”. Nutritionists should actively advise against harmful “dietary supplementation”. Distributive justice requires every patient to have an equal opportunity to obtain appropriate therapy. There are relatively few nutritionists and dieticians in South Africa, and indeed in the entire African continent, but proportionately even fewer in the areas of greatest need. A case illustrates the application of these ethical principles to show how they can be applied to our daily practice. Using these four principles is a practical approach to solving ethical dilemmas.
Microwave-Assisted Polyesterification Process in Bulk and Aqueous Media  [PDF]
Nassima Mazouzi-Sennour, Franois Henry
International Journal of Organic Chemistry (IJOC) , 2014, DOI: 10.4236/ijoc.2014.41003
Abstract: Microwave irradiation in polymer chemistry is an emerging research field. This type of heating can enhance the rate of reaction and improve the specific characteristics of the formed polymer. In this context, the present paper focuses on selective microwave (MW) heating and its influence on the polyesterification reaction. As a reaction model, the polyesterification of sebacic acid with decanediol, in bulk and in aqueous emulsion is investigated. The reaction was catalyzed by using 4-dodecylbenzenesulfonic acid (DBSA), which plays a catalytic and surfactant role. Both in bulk and in aqueous media, a polyester with higher molecular weight is obtained in MW heating compared to the conventional heating.
Influence of Microwave Irradiation on Hydrolysis Reaction of Sunflower Oil in Aqueous Emulsion  [PDF]
Nassima Mazouzi-Sennour, Franois Henry
International Journal of Organic Chemistry (IJOC) , 2014, DOI: 10.4236/ijoc.2014.41004
Abstract: Microwave irradiation (MW) has been widely applied as heating in chemical processing. It offers a clean, convenient and inexpensive method of heating which often results in higher yields and shorter reaction times. Here, we study the microwave heating influence on the hydrolysis of the triglyceride (sunflower oil) in aqueous emulsion catalyzed by using 4-dodecylbenzenesulfonic acid (DBSA). The progress of the hydrolysis reaction was determined by Fourier Transform Infrared spectroscopy (FTIR). The effects of temperature, reaction time and the catalyst nature and concentration on the hydrolysis reaction were investigated. The hydrolysis was carried out at temperatures ranging between 90°C and 150°C. The polarity of the reaction medium accelerated this reaction.
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