Caractérisation du comportement mécanique d'un composite (tissu de verre/résine époxyde) à différentes périodes de vieillissement hygrothermiques

Characterization of the mechanical behaviour of composite (woven fabric glass/epoxy resin) at different times during hygrothermal ageingThis paper considers the analysis of the mechanical behaviour of a laminate constituted of 12 layers of glass fiber fabric/epoxy resin conditioned at different relative humidities of 0, 60 and 96 % at 60 °C. The analysing of the experimental results obtained of hygrothermal ageing on the mechanical response has permited to show that the influence of the moisture concentration on the ultimate mechanical properties becomes significant and  important  for the composite conditioned at relative humidity of 96 % to the periods I and II (state of saturation and ageing)

Identification method of structural defects in glass fiber fabric/epoxy resin laminate

We present the experimental methods proposed for the identification of structural defects of the laminate constituted of 12 layers of glass fiber fabric/epoxy resin. Two techniques of control were used to analyze the principal structural defects (local or global disorientation). The first technique provides a superficial observation (macroscopic analysis) of the superior and lower surfaces of each layer, while the second one ensures internal observation (microscopic analysis) of the different layers after pyrolysis of the matrix (delamination of the laminate).Описано експериментальні методи для ідентифікації структурних дефектів у 12-шаровому ламінаті на основі скловолокнистої тканини й епоксидної смоли. Для аналізу основних структурних дефектів (локальна або глобальна дезорієнтація) використовували два методи. Один метод забезпечує дослідження (макроаналіз) верхньої і нижньої поверхней кожного шару, інший - внутрішнє дослідження (мікроаналіз) кожного шару після піролізу матриці (деламінації ламінату).Описаны экспериментальные методы для идентификации структурных дефектов в 12-слойном ламинате на основе стекловолокнистой ткани и эпоксидной смолы. Для анализа основных структурных дефектов (локальная или глобальная дезориентация) использовались два метода. Один метод обеспечивает исследование (макроанализ) верхней и нижней поверхностей каждого слоя, другой - внутреннее исследование (микроанализ) каждого слоя после пиролиза матрицы (деламинации ламината)

Modeling of the mechanical behavior of composite at different relative humidities

The moisture diffusion and mechanical response in shear of a laminate constituted of 12 layers of glass fabric fiber/epoxy resin were evaluated. The experimental analysis of the moisture absorption of the specimens conditioned at different relative humidities, 0, 60, and 96% RH at 60°C was to determine the two parameters characteristic of the Fick diffusion law (the diffusion coefficient D and the maximum quantity of water of saturation Mm) which admits the reversibility of the phenomenon. The analysis of the mechanical response in shear of the specimens oriented at 45° tested in uniaxial tension at constant imposed displacement rates, has permitted to show that the influence of the moisture concentration for the composite is very important at 96% RH. The proposed simple model permits to specify the influence of water absorption on the mechanical behavior in shear.Для дванадцятишаруватого ламіната з матрицею з епоксидної смоли і скловолокон досліджено закономірності абсорбції вологи і механічної поведінки в умовах зсуву. Експериментальні дослідження абсорбції вологи зразками з ламіната за різних значень вологості повітря (0, 60 і 96%) при температурі 60°C дозволили визначити два параметри (коефіцієнт дифузії D і максимальну кількість вологи при насиченні M m), що характеризують закон дифузії Фіка, який припускає зворотність процесу. Аналіз механічної поведінки при зсуві, що забезпечується одновісним розтягом ламіната з волокнами, орієнтованими під кутом 45° до осі розтягу, при постійних швидкостях переміщення показав, що при вологості 96% концентрація вологи в композиті грає особливо важливу роль. Запропоновано просту модель, яка дозволяє описати вплив абсорбції вологи на механічну поведінку ламіната при зсуві.Для 12-слоистого ламината с матрицей из эпоксидной смолы и стекловолокон исследованы закономерности абсорбции влаги и механического поведения в условиях сдвига. Экспериментальные исследования абсорбции влаги образцами из ламината при различных значениях влажности воздуха (0, 60 и 96%) при температуре 6WC позволили определить два параметра (коэффициент диффузии D и максимальное количество влаги при насыщении Mm), характеризующих закон диффузии Фика, который предполагает обратимость процесса. Анализ механического поведения при сдвиге, обеспечиваемом одноосным растяжением ламината с волокнами, ориентированными под углом 45° к оси растяжения, при постоянных скоростях перемещения показал, что при влажности 96% концентрация влаги в композите играет особенно важную роль. Предложена простая модель, позволяющая описать влияние абсорбции влаги на механическое поведение ламината при сдвиге

Effect of Industrial By-products Fillers on the Properties of Blended Cements in Sulphate Environments

International audienceIn previous studies, we have investigated the durability of normal concrete in various sulphates environments. The contribution of this study is the addition of industrial by-products fillers: granulated blast furnace slag and marble powder. These two fillers do not need any calorific energy compared to clinker manufacturing. From an environmental perspective, no more carbon dioxide is produce when these two materials are used. Furthermore, slag and powder marble are waste that should be stocked in adapted landfills. Samples of normal mortar were exposed for 12 months to two sulphate environments: ammonium sulphate and sulphuric acid at two concentrations (0.05 and 0.25 mol/L). The evolution of crystalline phases is analyzed by XRD and minerals are observed by SEM, microanalysis (EDS linked to SEM) confirms their chemical composition. These determinations involve both the superficial formations that internal training due to conservation bath. For a low concentration of suphate (0.05 mol/L), the results show that the crystalline phases of cement (CSH, CH, ettringite) seem unaffected in the interior of the sample where the sulphur is completely absent. On the other hand, the ammonium sulphate penetrates deeper (4mm) to a high concentration (0.25 mol/L). However in the case of attack by sulphuric acid, samples develop a dense surface gypsum deposit. The mechanical strength, including bending strength to be known very sensitive to surface, is important to study this durability

Particle swarm optimization for tuning PSS-PID controller of synchronous generator

In this paper the design an optimal PSS-PID controller for single machine connected to an infinite bus (SMIB). We presented a novel application of particle swarm optimization (PSO) for the optimal tuning of the new PSS-PID controller. The proposed approach has superior features, including easy implementation, stable convergence characteristic and good computational efficiency. The synchronous generator is modeled and the PSO algorithm is implemented in Simulink of Matlab. The obtained results have proved that (PSO) are a powerful tools for optimizing the PSS parameters, and more robustness of the system IEEE SMIB

The effect of mechanical activation of cements with mineral admixtures on the mechanical strength of concrete

The objective of this experimental study consists in studying the influence of the fineness (specific surface) of cements with mineral additions on the mechanical strength of the concrete. This work is a contribution to the improvement of the properties of the concretes by mechanical activation of two types of cements (C.E.M II) manufactured in various cement factories (cements with various mineral additions : slag and tuff). The physical properties of cements (C.E.M II) activated mechanically at anhydrous state and the state hydrated (specific weight, consistency of the cement pastes, setting times and shrinkage) thus the characteristics of the concretes made at their bases, such as, the mechanical behavior (compressive strength for the concrete) were studied. According to the experimental results obtained, it comes that the increase of the specific surface and the chemical composition of cements to the mineral additions are the principal responsibles to the improvement of the latent reactivity of mineral additions and increase the mechanical strengths of the concretes. Journal of Civil Engineering Research and Practice Vol. 3(1) 2006: 65-7

Proposition d'un modèle expérimental pour la caractérisation de la réponse mécanique d'un composite (tissu de verre / résine époxyde)

L'objet de cet article est de proposer une géométrie d'éprouvette pour la caractérisation de la réponse mécanique d'un composite constitué de 12 plis de tissus de fibres de verre noyé dans une résine époxyde. Des essais de traction uniaxiale en rampe monotone réalisés sur différentes configurations géométriques d'éprouvettes avec différentes vitesses d'essais et le calcul numérique par éléments finis de la répartition des contraintes dans la zone centrale du modèle expérimental proposé, nous ont permis de justifier le choix d'une éprouvette profilée avec un rayon de 1000 mm qui présente une section réduite au centre et pour laquelle la rupture survient dans la zone centrale sans chute notable des caractéristiques mécaniques ultimes par rapport à l'éprouvette de forme parallélépipédique

Path integration in tactile perception of shapes

Whenever we move the hand across a surface, tactile signals provide information about the relative velocity between the skin and the surface. If the system were able to integrate the tactile velocity information over time, cutaneous touch may provide an estimate of the relative displacement between the hand and the surface. Here, we asked whether humans are able to form a reliable representation of the motion path from tactile cues only, integrating motion information over time. In order to address this issue, we conducted three experiments using tactile motion and asked participants (1) to estimate the length of a simulated triangle, (2) to reproduce the shape of a simulated triangular path, and (3) to estimate the angle between two-line segments. Participants were able to accurately indicate the length of the path, whereas the perceived direction was affected by a direction bias (inward bias). The response pattern was thus qualitatively similar to the ones reported in classical path integration studies involving locomotion. However, we explain the directional biases as the result of a tactile motion aftereffect