45 research outputs found
Nonlinear continuum damage models for ceramic matrix composites with significant in plane ply anisotropy
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Robust characterization of crack propagation in 3D woven composites and evidences of size dependency
International audienceThe failure of fibers inside the yarns of 3D woven carbon/epoxy composites is investigated experimentally by estimating the critical energy release rate GC, through the analysis of Compact Tension (CT) and Single Edge Notched Beam (SENB) specimens. Close attention is paid to the specimen design as well as the tracking of the crack growth. Several data analysis methods are compared in order to obtain a valid process for highly anisotropic materials such as 3D woven composites with a relatively large Representative Elementary Volume (REV). Variation of GC with the specimen size and geometry is obtained and evidences of the invalidity of the Linear Elastic Fracture Mechanics (LEFM) framework for 3D woven composites are highlighted
Biomechanical evolution of solid bones in large animals: a microanatomical investigation
International audienc
Maternal and fetal genetic effects on birth weight and their relevance to cardio-metabolic risk factors.
Birth weight variation is influenced by fetal and maternal genetic and non-genetic factors, and has been reproducibly associated with future cardio-metabolic health outcomes. In expanded genome-wide association analyses of own birth weight (nâ=â321,223) and offspring birth weight (nâ=â230,069 mothers), we identified 190 independent association signals (129 of which are novel). We used structural equation modeling to decompose the contributions of direct fetal and indirect maternal genetic effects, then applied Mendelian randomization to illuminate causal pathways. For example, both indirect maternal and direct fetal genetic effects drive the observational relationship between lower birth weight and higher later blood pressure: maternal blood pressure-raising alleles reduce offspring birth weight, but only direct fetal effects of these alleles, once inherited, increase later offspring blood pressure. Using maternal birth weight-lowering genotypes to proxy for an adverse intrauterine environment provided no evidence that it causally raises offspring blood pressure, indicating that the inverse birth weight-blood pressure association is attributable to genetic effects, and not to intrauterine programming.The Fenland Study is funded by the Medical Research Council (MC_U106179471) and
Wellcome Trust
Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches
Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly
L'insuffisance cardiaque au Centre Hospitalier de Vienne (étude descriptive et recherche de facteurs de réhospitalisation)
LYON1-BU Santé (693882101) / SudocSudocFranceF
Analyse expĂ©rimentale et numĂ©rique de la tenue de matĂ©riaux composites tissĂ©s 3D : de lâĂ©prouvette Ă©lĂ©mentaire aux structures aĂ©ronautiques complexes
International audienceNew generations of 3D woven composite materials have been recently developed to be used in aeronautics as an alternative to the classical laminated composite materials, for structures exposed to impact. Therefore, it has been necessary to determine precisely the damage and failure scenarios for such materials subjected to different kinds of loadings through a large experimental testing campaign performed at Onera on unnotched coupons. These tests have been multi-instrumented to understand the different damage and failure mechanisms encountered in 3D woven composite materials. Based on these observations, a model, named Onera Damage Model for Polymer Matrix Composites (ODM-PMC), has been developed specifically for such materials. This non-linear material approach takes into account the different observed sources of non-linearity (viscoelasticity of the matrix, inâplane matrix damage, interyarn debondings and fiber yarn failures) and has been validated through comparisons with available tests on unnotched specimens. Moreover, the predicted failure loads, obtained with the ODM-PMC model, on plates containing different kinds of geometrical singularities, such as a hole or a milled groove, have been compared successfully to multi-instrumented test results also performed at Onera . Finally, the ODM-PMC model has been applied to large 3D woven composite structures, quite representative of real industrial components. The predicted damage and failure scenarios seem to be relevant as compared to data available in the literature. Moreover, the obtained computational times are compatible with usage in an industrial environment. Therefore, it has been demonstrated that this approach, implemented in a commercial finite element code, could be used in design offices in aeronautical industries.Les nouvelles gĂ©nĂ©rations de matĂ©riaux composites tissĂ©s 3D Ă matrice organique ont rĂ©cemment Ă©tĂ© dĂ©veloppĂ©es pour ĂȘtre utilisĂ©es dans l'aĂ©ronautique comme une alternative aux matĂ©riaux composites stratifiĂ©s classiques, pour des structures exposĂ©es aux impacts. Par consĂ©quent, il a Ă©tĂ© nĂ©cessaire dâĂ©tudier finement les endommagements et dâĂ©tablir les scĂ©narios de rupture de ces matĂ©riaux soumis Ă diffĂ©rents types de chargement Ă lâaide dâune importante campagne dâessais mĂ©caniques effectuĂ©s Ă l'ONERA sur des Ă©prouvettes Ă©lĂ©mentaires. Ces essais ont Ă©tĂ© multi-instrumentĂ©s afin de comprendre les diffĂ©rents mĂ©canismes dâendommagement et de rupture rencontrĂ©s dans les matĂ©riaux composites tissĂ©s 3D. Sur la base de ces observations, un modĂšle, appelĂ© ONERA Damage Model pour Composites Ă Matrice Organique (ODM-CMO), a Ă©tĂ© dĂ©veloppĂ© spĂ©cifiquement pour ces matĂ©riaux. Ce modĂšle matĂ©riau non linĂ©aire prend en compte les diffĂ©rentes sources de non-linĂ©aritĂ© observĂ©es (viscoĂ©lasticitĂ© de la matrice, fissuration matricielle, dĂ©cohĂ©sions inter-torons et la rupture des torons de fibres) et a Ă©tĂ© validĂ© au travers de comparaisons avec les rĂ©sultats dâessais disponibles sur des Ă©prouvettes Ă©lĂ©mentaires. Par ailleurs, les efforts Ă rupture, prĂ©vus par le modĂšle ODM-CMO, sur des plaques contenant diffĂ©rents types de singularitĂ©s gĂ©omĂ©triques, telles que des trous ou des rainures fraisĂ©es, ont Ă©tĂ© comparĂ©s avec succĂšs aux rĂ©sultats des essais multi-instrumentĂ©s Ă©galement effectuĂ©s Ă l'ONERA. Enfin, le modĂšle ODM-CMO a Ă©tĂ© appliquĂ© Ă des structures composites tissĂ©es 3D reprĂ©sentatives de composants industriels. Les scĂ©narios dâendommagement et de rupture prĂ©vus semblent ĂȘtre cohĂ©rents avec les rĂ©sultats disponibles dans la littĂ©rature. De plus, les temps de calcul obtenus sont conformes aux exigences industrielles actuelles. Par consĂ©quent, il a Ă©tĂ© dĂ©montrĂ© que cette approche, disponible dans un code Ă©lĂ©ments finis commercial, pourrait ĂȘtre utilisĂ©e dans les bureaux d'Ă©tudes de lâindustrie aĂ©ronautique
ModÚles continus d'endommagement à variables scalaires non linéaires pour les composites à matrice céramique avec une anisotropie significative
International audienceContinuous fiber reinforced ceramic matrix composites (CMCs) are increasingly being employed in safety critical applications and the need the need for damage models to support the design, certification and sustainment has increased. In this work, we propose a simple but robust formulation for a 2D continuum damage model derived via a thermodynamics-based approach called openDM. Specifically, we consider a model with two scalar damage parameters that account for damage as a result of matrix cracking in the ply in both the fiber and transverse directions. The applicability of this model is considered for both a balanced 2D woven based SiC fiber reinforced composite and a 2D unidirectional ply based SiC fiber reinforced composite with predominately SiC matrices. While the response of the 2D woven composite was captured well with the two parameter model, the more anisotropic unidirectional ply based CMC was more difficult to capture unless a hybrid [0,90] ply was assumed in the model.Les composites à matrice céramique (CMC) renforcés par des fibres continues sont de plus en plus utilisés dans des applications critiques en matiÚre de sécurité et le besoin de modÚles d'endommagement pour soutenir la conception, la certification et le maintien en service a augmenté. Dans ce travail, nous proposons une formulation simple mais robuste pour un modÚle d'endommagement continu 2D dérivé d'une approche thermodynamique. Plus précisément, nous considérons un modÚle avec deux paramÚtres d'endommagement scalaires qui tiennent compte de l'endommagement résultant de la fissuration de la matrice dans le pli, à la fois dans la direction des fibres et dans la direction transversale. L'applicabilité de ce modÚle est considérée à la fois pour un composite 2D tissé équilibré renforcé par des fibres de SiC et un composite 2D unidirectionnel renforcé par des fibres de SiC avec une matrice prédominante de SiC. Alors que la réponse du composite tissé 2D a été bien capturée avec le modÚle à deux paramÚtres, la réponse du CMC à base de plis unidirectionnels plus anisotropes a été plus difficile à capturer, à moins de supposer un pli hybride 0-90
Analyse de la tenue dâĂ©prouvettes trouĂ©es composites tissĂ©es 3D sous sollicitations de compression au moyen dâun dialogue essais/calculs
Dans cette Ă©tude, une campagne dâessais de compression sur Ă©prouvettes trouĂ©es en
matĂ©riau tissĂ© 3D a Ă©tĂ© rĂ©alisĂ©e. Cette campagne vise Ă ÂŽetudier lâinfluence de lâeffet
dâĂ©chelle sur la tenue dâĂ©prouvettes trouĂ©es. Les observations expĂ©rimentales sont ensuite
comparées à des résultats obtenus par simulations éléments finis. Trois méthodes de
prĂ©vision de la ruine dâĂ©prouvettes trouĂ©es, de complexitĂ© croissante, sont Ă©tudiĂ©es : (i)
la méthode du Point Stress, (ii) la méthode du Volume Caractéristique de Rupture et (iii)
un modÚle de rupture de fibres progressif appelé ODM-CMO. Les prévisions en termes de
scenario dâendommagement et de force Ă rupture sont comparĂ©es aux rĂ©sultats dâessais
disponibles et les effets dâĂ©chelle spĂ©cifiques Ă ces matĂ©riaux sont discutĂ©s