Reconstruction de champ par identification des conditions aux limites : Principes et Applications

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/28/23/ANNEX/r_68GLWI89.pd

Modèle multi-échelles et mesures de l'endommagement pour optimiser l'utilisation des structures composites stratifiées

International audienceBien que les modèles d'évolution et les mesures d'endommagement aient fait de grands progrès, la rupture des structures composites stratifiées reste un phénomène mal-maîtrisé, à la fois complexe et multi-échelle. En associant la modélisation et la mesure de l'endommagement, nous proposons une approche pour optimiser l'utilisation des structures composites stratifiées tout au long de leur durée de vie, depuis la validation de modèle jusqu'à l'analyse de la rupture. Cette approche s'appuie sur les mesures obtenues par micro-tomographie ainsi que sur le modèle développé au LMA. Ces mesures sont utilisées dans un premier temps pour valider le modèle de comportement. Dans un second temps, nous nous intéressons à l'estimation de la durée de vie des structures ainsi qu'à leur expertise post-rupture à partir de l'utilisation conjointe du modèle et des mesure d'endommagement

Particle Measurement Programme (PMP) Heavy-Duty (HD) Inter-laboratory Exercise: Exploratory Work at JRC (Oct2007 - Feb2008)

This document reports the results of the exploratory work during the PMP Heavy-Duty inter-laboratory exercise - from Oct. '07 to Feb. '08 - conducted at the Vehicles Emissions Laboratory (VELA-5) in the Transport and Air Quality Unit of the European Commission¿s Joint Research Centre (JRC, Ispra). This report presents the results of the work undertaken on an IVECO Cursor 8 Heavy-Duty engine equipped with a Continuous Regenerating Trap (CRT), i.e. the Golden Engine. Main objective of these tests were to finalize the measurement protocol that will be used in the validation exercise and the round robin. These tests included background tests, filter media effect, filter face velocity, preconditioning effect, comparisons of different particle number systems, and investigation of the golden instruments.JRC.H.4-Transport and air qualit

EU project UPGRADE (No 724036) - measurements of a Jeep Renegade prototype vehicle by JRC

Within Work Package 5 of the H2020 project UPGRADE (High efficient Particulate free Gasoline Engines) http://www.upgrade-project.eu/, JRC tested a demonstrator vehicle specifically developed by Centro Ricerche Fiat (CRF) in WLTP conditions. The results showed that: 1. All pollutants were below the EURO 6 limits. 2. Particle number emissions were two orders of magnitude below the limit of 6*10^11/km. PN10 were in average 13% higher than PN23. 3. CO2 emissions were on average 165.3 g/km.JRC.C.4-Sustainable Transpor

Failure analysis of composite bolted joints by an experimental and numerical approach

Composite materials are widely used by aircraft manufacturers because of their high mechanical properties. These properties severely decrease when composite material are drilled and bolted. To avoid structural failure, the behavior of composite bolted joints has to be understood and mastered. An experimental database was constituted by Dassault Aviation with supported single-shear tests with countersunk head screws on different composite materials. This database is analysed to find the main parameters that lead to the failure of the joint. The end distance is the most important parameter. It has a strong influence on both the bearing stress at failure and the failure mode. Width and lay-up have a lower effect on joint failure. A two-dimensional finite element (FEM) model with elastic membrane behavior is then developed to simulate the different configurations in the database. Fiber failure criteria is computed and the dispersion of the results for each failure mode is compared to the dispersion of the experimental data to evaluate the quality of the model. The modification of the failure criteria by taking into account different ply orientations and shear stress permits to reduce the dispersion but it is still higher than the dispersion of the experimental data. This work highlights the limits of such linear 2D modelling and it confirms the needs for more complex modelling such as the local bending effects of the joints and/or the non linear behavior of the composite material

Failure analysis of composite bolted joints by an experimental and a numerical approach

Composite materials are widely used by aircraft manufacturers because of their high mechanical properties. These properties severely decrease when composite material are drilled and bolted. To avoid structural failure, the behavior of composite bolted joints has to be understood and mastered. An experimental database was constituted by Dassault Aviation with supported single-shear tests with countersunk head screws on different composite materials. This database is analysed to find the main parameters that lead to the failure of the joint. The end distance is the most important parameter. It has a strong influence on both the bearing stress at failure and the failure mode. Width and lay-up have a lower effect on joint failure. A two-dimensional finite element (FEM) model with elastic membrane behavior is then developed to simulate the different configurations in the database. Fiber failure criteria is computed and the dispersion of the results for each failure mode is compared to the dispersion of the experimental data to evaluate the quality of the model. The modification of the failure criteria by taking into account different ply orientations and shear stress permits to reduce the dispersion but it is still higher than the dispersion of the experimental data. This work highlights the limits of such linear 2D modelling and it confirms the needs for more complex modelling such as the local bending effects of the joints and/or the non linear behavior of the composite material

Analyse non linéaire par éléments finis d’assemblages composites boulonnés : comparaison essais-calculs

Les matériaux composites à base de fibres de carbone et matrice organique sont très utilisés dans l’industrie aéronautique pour leurs très bonnes propriétés mécaniques. Cependant ces propriétés chutent considérablement lorsque les matériaux composites sont percés et boulonnés. Afin d’éviter la ruine de la structure, il est important de maitriser le comportement des assemblages composites boulonnés. Une loi de comportement endommageable pour les matériaux composites développée à l’Institut Clément Ader (ICA) est utilisée dans des modèles éléments finis afin de simuler le comportement d’éprouvettes de simple cisaillement soutenues et de double cisaillement. Un modèle plan avec un comportement de membrane est suffisant pour simuler correctement des essais de double cisaillement. Cependant ce type de modèle ne permet pas de représenter fidèlement un essai de simple cisaillement en raison des phénomènes hors plan qui se produisent. Un modèle de plaque est donc utilisé pour ce type d’essai. Des scenarios d’endommagement sont alors élaborés afin d’identifier les dégradations du matériau composite qui mènent à la chute de la raideur de la structure. La rupture des fibres en compression puis en traction dans les plis orientés à 0° est la principale cause de cette chute de raideur

Nonlinear finite element analysis of composite bolted lap joints: experimental vs numerical tests

Carbon fiber reinforced plastics (CFRP) are widely used in aircraft industry because of their high mechanical properties. However these properties considerably drop when composite materials are drilled and bolted. Thus it is important to master the composite bolted joints behavior to avoid the structural failure. Progressive damage behavior for composite materials developed at Institut Clément Ader (ICA) is implemented on finite element (FE) models to simulate the behavior of supported single lap joints and double lap joints specimens. An in-plane shell model is sufficient to accurately simulate double lap joint tests. However this kind of model does not allow for an accurate representation for a single lap joint test because of the out of plane phenomena occurring during the test. A model with shell behavior is then developed. Damaging scenarios are elaborated to identify the composite material degradations leading to the structural stiffness loss. Compressive then tensile fiber failure in the 0° plies are the main reasons of this stiffness loss

Failure analysis of single lap composite laminate bolted joints: comparison of experimental and numerical tests

Carbon fiber reinforced plastics (CFRP) are widely used in aircraft industry because of their high mechanical properties. However these properties considerably drop when composite materials are drilled and bolted. Thus, it is important to master the composite bolted joint behavior to avoid a structural failure. Experimental test on single lap bolted joints with various end distance have been led. The failed specimens are analysed thanks to XR computed tomography (XR-CT) and digital image correlation (DIC). The results are compared with a three dimensional finite element model involving a progressive damage model for the composite material. It is based on a progressive damage model of the composite material. The global behavior and the damages computed are in good agreement with the experimental results. But, contrary to the experimental observations, the computed damage scenarios are the same for all the tested end distance