Reliability analysis and micromechanics: A coupled approach for composite failure prediction

This work aims at associating two classical approaches for the design of composite materials: first, reliability methods that allow to account for the various uncertainties involved in the composite materials behaviour and lead to a rational estimation of their reliability level; on the other hand, micromechanics that derive macroscopic constitutive laws from micromechanical features. Such approach relies on the introduction of variabilities defined at the microscale and on the investigation of their consequences on the material macroscopic response through an homogenization scheme. Precisely, we propose here a systematic treatment of variability which involves a strong link between micro- and macroscales and provides a more exhaustive analysis of the influence of uncertainties. The paper intends to explain the main steps of such coupling and demonstrate its interests for material engineering, especially for constitutive modelling and composite materials optimization. An application case is developed throughout on the failure of unidirectional carbon fibre-reinforced composites with a comparative analysis between experimental data and simulation results

Experimental analysis of short concrete column under hygrothermo-mechanical accelerated aging

Concrete was considered to be very durable material for a long time. However many constructions have shown degradations during their service life. To ensure safety, stability and serviceability of civil engineering structures, understanding of deterioration processes and their effect on the residual structural load capacity is necessary. This paper is based on the experimental study of short prismatic concrete columns under the hygrothermo-mechanical accelerated aging. To investigate the effects of the exposure conditions on the strength of specimens, combined ultrasonic pulse velocity testing and compression loading testing was used. It can be observed from the results obtained in this work that the ultrasonic pulse velocity measurements agree well with the experimental results obtained from the compression loading testing. Results indicate that in first time, degradation of specimens occurs slightly. After that the degradation becomes notable. It also indicates that the degradation due to the combined effect of the hygrothermo-mechanical aging is higher than when we consider hygrothermal and mechanical process separatel

Reliability and micromechanics of composite materials. Application to the Laroin footbridge

Les méthodes fiabilistes permettent d'évaluer le risque de défaillance d'une structure compte tenu des incertitudes mises en jeu. Les approches par changement d'échelle visent quant à elles à spécifier les relations entre les caractéristiques microstructurales des matériaux hétérogènes et leur loi de comportement macroscopique. Une association de ces deux démarches pour rendre compte de la fiabilité de structures composites est ici proposée. L'idée est d'évaluer l'effet sur la probabilité de défaillance de variabilités définies à l'échelle microscopique, le passage micro-macro étant réalisé par homogénéisation. L'intérêt est d'une part de contribuer à la compréhension de la défaillance de ces matériaux et, d'autre part, de mettre en oeuvre une procédure de validation enrichie des modèles micromécaniques. Cette étude s'appuie sur le cas de la passerelle de Laroin (Pyrénées Atlantiques), premier ouvrage en France réalisé à l'aide de haubans composites en carbone-époxy

Fiabilité et micromécanique des matériaux composites. Application à la passerelle de Laroin

Les méthodes fiabilistes permettent d'évaluer le risque de défaillance d'une structure compte tenu des incertitudes mises en jeu. Les approches par changement d'échelle visent quant à elles à spécifier les relations entre les caractéristiques microstructurales des matériaux hétérogènes et leur loi de comportement macroscopique. Une association de ces deux démarches pour rendre compte de la fiabilité de structures composites est ici proposée. L'idée est d'évaluer l'effet sur la probabilité de défaillance de variabilités définies à l'échelle microscopique, le passage micro-macro étant réalisé par homogénéisation. L'intérêt est d'une part de contribuer à la compréhension de la défaillance de ces matériaux et, d'autre part, de mettre en oeuvre une procédure de validation enrichie des modèles micromécaniques. Cette étude s'appuie sur le cas de la passerelle de Laroin (Pyrénées Atlantiques), premier ouvrage en France réalisé à l'aide de haubans composites en carbone-époxy. ABSTRACT : Reliability methods make it possible to evaluate the risk of failure of a structure according to the uncertainties involved in its mechanical behavior. On the other hand, micromechanics offers the most suitable framework to derive macroscopic constitutive laws from microstructural features. We propose here to associate these two approaches in order to account for the reliability of composite materials. The aim is to analyze the effect of variabilities defined at the microscale on the probability of failure through an homogenization scheme. Such coupling will help in understanding the failure mechanisms and also provides an improved validation for micromechanical models. This study is focused on the case of the Laroin footbridge, which is the first civil engineering structure in France made of composite stays in carbon-epox

Contribution of a micromechanics-based approach for reliability assessment

The paper intends to widely develop the use of a new methodology for the design and optimization of composite materials and structures. Based on the coupling of reliability methods and homogenization techniques, such approach allows the integration of uncertainties at different scales in the problem analysis (i.e. from the microscopic scale of the composite material components up to the macroscopic scale of the structure) and the investigation of their consequences in the failure prediction. The principles and implementation steps of such original method have already been described in details (Int. J. Mech. Sci. 53 (2011) 935-945; Eng. Fail. Analysis 18 (2011) 988-998). This work focuses on its application and significant progress allowed in the design phase for engineering composite materials. Illustrations are presented on the case of a civil engineering structure, namely the Laroin footbridge (France) with carbon epoxy stay cables, and highlight reliability-based innovations and exploitations regarding the structure optimization

Experimental analysis of short confined columns

International audienceThe reinforcement of a concrete structure consists in improving the mechanical characteristics of the elements that compose it, so that it offers a better reliability both in service state and state of ultimate strengths. In this study, we propose to develop new technical solutions to improve the properties and strength of concrete through internal confinement

Multilevel assessment method for reliable design of composite structures

This work aims at demonstrating the interest of a new methodology for the design and optimization of composite materials and structures. Coupling reliability methods and homogenization techniques allow the consideration of probabilistic design variables at different scales. The main advantage of such an original micromechanics-based approach is to extend the scope of solutions for engineering composite materials to reach or to respect a given reliability level. This approach is illustrated on a civil engineering case including reinforced fiber composites. Modifications of microstructural components properties, manufacturing process, and geometry are investigated to provide new alternatives for design and guidelines for quality control

Multi-scale reliability analysis of composite structures – Application to the Laroin footbridge

This work aims at developing a new methodology for the reliability assessment of composite structures and their design optimization. It relies on the coupling of well established methods: homogenization scheme for the mechanical modelling of composite materials and reliability methods to account for their inherent variability. Moreover, such approach is based on an accurate treatment of inherent uncertainties of these mechanical systems at various scales, including microscopic and macroscopic levels, that provides newperspectives for structural design. As an illustration, we propose to apply the multi-scale reliability analysis on the case of the Laroin footbridge (France) with carbon–epoxy stay cables. Since the reliability assessment of such structure is evaluated through the fibre failure, numerical simulations require the coupling of reliability methods, finite element modelling to derive macroscopic loading within cables and micromechanics to estimate the effective elastic properties of composite and local responses within constituents. Results demonstrate the feasibility of the coupled approach at a structure scale and its main interests for the optimization phase of materials and engineering structures

Fiabilité et micromécanique des matériaux composites (application à la passerelle de Laroin)

Les méthodes fiabilistes permettent d'évaluer le risuqe de défaillance d'une structure compte tenu des incertitudes mises en jeu. Les apporches par changement d'échelle visent quant à elles à spécifier les relations entre les caractéristiques microstructurales des matériaux hétérogènes et leur loi de comportement macroscopique. Une association de ces deux démarches pour rendre compte de la fiabilité de structures composites est ici proposée. L'idée est d'évaluer l'effet sur la probabilité de défaillance de ces matériaux et, d'autre part, de mettre en oeuvre une procédure de validation enrichie des modèles micromécaniques. Cette étude s'appuie sur le cas de la passerelle de Laroin (Pyrénées Atlantiques), premier ouvrage en France réalisé à l'aide de haubans composites en carbone-époxy.Reliability methods make it possible to evaluate the risk of failure of a structure according to the uncertainties involved in its mechanical behavior. On the other hand, micromechanics offers the most suitable framework to derive macroscopic constitutive laws from microstructural features. We propose here to associate these two approaches in order to account for the reliability of composite materials. The aim is to analyze the effect of variabilities defined at the microscale on the probability of failure through an homogenization scheme. Such coupling will help in understanding the failure mechanisms and also provides an improved validation for micromechanical models. This study is focused on the case of the Laroin footridge, which is the first civil engineering structure in France made of composite stays in carbon-epoxy.TOULOUSE-ENSEEIHT (315552331) / SudocTARBES-ENIT (654402301) / SudocSudocFranceF