Hypoelastic, hyperelastic, discrete and semi-discrete approaches for textile composite reinforcement forming

International audienceThe clear multi-scale structure of composite textile reinforcements leads to develop continuous and discrete approaches for their forming simulations. In this paper two continuous modelling respectively based on a hypoelastic and hyperelastic constitutive model are presented. A discrete approach is also considered in which each yarn is modelled by shell finite elements and where the contact with friction and possible sliding between the yarns are taken into account. Finally the semi-discrete approach is presented in which the shell finite element interpolation involves continuity of the displacement field but where the internal virtual work is obtained as the sum of tension, in-plane shear and bending ones of all the woven unit cells within the element. The advantages and drawbacks of the different approaches are discussed

Essais de caractérisation des structures tissées

Dans ce travail, on s\u27intéresse à l\u27étude et la modélisation de comportement mécanique de structure tissée. On commence par présenter les propriétés des matériaux testés grâce aux essais de caractérisation. Une base des données expérimentales est constituée afin d\u27analyser le comportement mécanique du tissu sous certaines sollicitations, et en particulier le cisaillement, moyennant la technique de corrélation d\u27image. Ensuite, en adoptant une approche hyperélastique, un modèle simplifié est développé permettant d\u27étudier numériquement l\u27influence de rapport des rigidités de traction et de cisaillement sur le comportement mécanique tissu suite à une extension à 45 . Enfin, en se basant sur approche phénoménologique, une loi de comportement hyperélastique en puissance est proposée. Ce modèle est implanté dans une routine Vumat d\u27Abaqus/Explicit. Il est identifié à partir des essais de traction et de cisaillement et validé par certains cas de mise en forme des renforts tissés

Essais de caractérisation des structures tissées

Dans ce travail, on s'intéresse à l'étude et la modélisation de comportement mécanique de structure tissée. On commence par présenter les propriétés des matériaux testés grâce aux essais de caractérisation. Une base des données expérimentales est constituée afin d'analyser le comportement mécanique du tissu sous certaines sollicitations, et en particulier le cisaillement, moyennant la technique de corrélation d'image. Ensuite, en adoptant une approche hyperélastique, un modèle simplifié est développé permettant d'étudier numériquement l'influence de rapport des rigidités de traction et de cisaillement sur le comportement mécanique tissu suite à une extension à 45 . Enfin, en se basant sur approche phénoménologique, une loi de comportement hyperélastique en puissance est proposée. Ce modèle est implanté dans une routine Vumat d'Abaqus/Explicit. Il est identifié à partir des essais de traction et de cisaillement et validé par certains cas de mise en forme des renforts tissés.In this work, we interested to the study and the modelling of mechanical behaviour of weave structure. We begin by presenting the properties of tested materials thanks to tests of characterization. An experimental data base is established to analyze the mechanical behaviour of fabric under some solicitations, in particular the shear, using the technique of digital image correlation. Then, by adopting a hyperelastic approach, a simplified model is developed allowing to study numerically the influence of the report of tensile and shearing rigidities on the mechanical behaviour of woven fabric, further to an extension in 45 . Finally, by basing on phenomenological approach, a hyperelastic behaviour law is proposed. This model is implanted in a routine Vumat. It is identified from the tensile and the shearing tests and validated by certain cases of composite reinforcement forming.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

24-Epibrassinolide ameliorates the adverse effect of salt stress (NaCl) on pepper (Capsicum annuum L.)

The present study investigates the role of 24-epibrassinolide (EBL) in inducing plant tolerance to salinity. Seedlings of pepper (Capsicum annuum L.) were grown in the presence of 70 mM NaCl and were sprayed with 10-6 M EBL at 7 days after transplantation and were sampled at 28 day. The plants exposed to NaCl exhibited a significant decline in relative growth rate, net CO2 assimilation, stomatal conductance, transpiration and water use efficiency. However, the follow up treatment with EBL significantly improved the above parameters. EBL treated plants had greater relative growth rate compared to untreated plants when exposed to salt stress. Application of EBL increased photosynthesis by increasing stomatal conductance in both control and salt stressed plants and may have contributed to the enhanced growth. The water use efficiency was improved because CO2 assimilation is more important than the transpiration

264: Myeloperoxidase, hs CRP and endothelial dysfunction in cardiovascular risk assessment in diabetic and hypertensive patients

IntroductionSeveral inflammatory markers have been associated with a greater likelihood of cardiovascular diseases. Of those C-reactive protein (CRP) and myeloperoxidase (MPO) are the most well known.The development of sensitive rapid tests for MPO and hs-CRP, together with a simple hand-held reader promises to open up the possibility of identifying high-risk patients early enough for the introduction of prophylactic therapies or the adoption of beneficial life-style changes.ObjectivesWe propose to evaluate the cardiovascular risk for 50 hypertensive and diabetic patients by rapid tests for MPO and hs-CRP and to compare with endothelial function and Framingham score.ResultsWe evaluate prospectively 50 patients without cardiovascular events, the mean age is 53 years, 78% have mean or high CV risk according to the Framingham score and 38% presenting endothelial dysfunction.The statistical analysis showed a significant association between the rate of hs-CRP, the Framingham score (p=0,02, r=0,424), with the metabolic syndrome (p=0,0001), and endothelial dysfunction (p=0,001).MPO level is correlated with the sex (p=0,002), age (p=0,05), as well with the Framingham score (r=0,345), the metabolic syndrome (p=0,001), the endothelial dysfunction (p=0,001), and also with the LDL cholesterol. (p=0,04; r=0,3).In the same way, a significant Correlation was shown between hs-CRP and MPO (p=0,016; r=0,34).The hs-CRP test showed a good specificity (85%), and VPP (96%), a weak VPN (27%).However MPO test showed a low specificity (25%) low sensitivity (25%), VPP of (73%) and a low VPN (5%).ConclusionThe hs-CRP represents the inflammatory marker most relevant in the prediction of risk CV, better than the MPO.These markers reflect the clinical potential of atherothrombotic disease may allow more precise risk stratification and prognostication in high-risk populations, and perhaps earlier diagnosis and intervention in patients at risk for or with occult cardiovascular disease