Peyroux Robert

French National Centre for Scientific Research | CNRS · Laboratoire 3SR - Sols, Solides, Structures, Risques

The aim of this experimental research is to investigate the effect of different alkali solutions, their different concentration, and the soaking time on tensile strength of bamboo fiber bundles. The results of this research will suggest the method to extract bamboo fiber in order to develop biodegradable composite materials in the future. Bamboo st...

The aim of this experimental research is to investigate the effect of different alkali solutions, their different concentration, and the soaking time on tensile strength of bamboo fiber bundles. The results of this research will suggest the method to extract bamboo fiber in order to develop biodegradable composite materials in the future. Bamboo st...

In order to fabricate bamboo hand sheet/Green Epoxy composites (BHGECs), the individual bamboo fibers are extracted by using chemical solutions. The bamboo fibers are then used to make bamboo hand sheet before being combined with Green Epoxy. The compatibility of fiber and matrix is directly affected by the extracted bamboo fiber shape. The objecti...

Chromatogeny grafting is an efficient method to hydrophobize lignocellulosic materials. Grafted papers are good candidates to replace plastic products in several applications requiring water barrier properties such as food packaging. However, chromatogeny grafting tends to reduce the sealability which is currently limiting the development of these...

In order to improve the tensile strength of bamboo hand sheets used as reinforcement in bio composite materials, bamboo fibers have to be arranged roughly in the same direction. However, the classical method for forming the bamboo hand sheet (using L’HOMARGY machine) is not efficient to align the fibers. The objective of this work is to improve the...

In order to use bamboo as reinforcement in composite material, we first need to extract individual fibers from bamboo strips and re-fabricated as hand sheets. Those hand sheets contain millions of individual fibers contacting each other by their surface force and mainly hydrogen bonding. Therefore, different NaOH concentration used during the extra...

The two on-going sample return space missions, Hayabusa2 and OSIRIS-REx are going to return to Earth asteroid regolith from the carbonaceous near-Earth asteroids Ryugu and Bennu. The two main processes that lead to regolith production are the micrometeorite bombardment and the thermal cracking. Here we report the production of a weak simulant mater...

Ultrasonic welding is a serious candidate in the development of methods to assemble papers and paperboards without using additional substances. However, the ultrasonic welding of papers remains a technological challenge considering the low weldability of lignocellulosic materials. This study aims to investigate on the ultrasonic welding process app...

Today's environmental concerns are pressuring industries to substitute paper-based materials in place of plastics in many sectors including packaging. However, assembling papers and paperboards using environmentally friendly solutions remains a technological challenge. In this context, ultrasonic (US) welding is an alternative to adhesives. In this...

Effects of root growth on soil has an important role in soil strength as is thus of interest for geotechnical engineering. This paper reveals the importance of initial bulk density on the response of soil to plant root evolution. Root-soil interaction is investigated through the growth of maize roots in sand with two bulk densities. A 3D timeseries...

An experimental study of the ultrasonic compression moulding (UCM) to manufacture biobased composites made of semicrystalline starch powders and softwood fibres is described. The main objective was to assess the potential of using this fast and economical processing technique to elaborate a 100% biobased composite which might substitute more usual...

The two on-going sample return space missions, Hayabusa2 and OSIRIS-REx are going to return to Earth asteroid regolith from the carbonaceous near-Earth asteroids Ryugu and Bennu. The two main processes that lead to regolith production are the micrometeorite bombardment and the thermal cracking. Here we report the production of a weak simulant mater...

Paper-based packaging materials are generally assembled using adhesives formulated with oil-based polymers. These adhesives make the recyclability of the materials more complex and may be the source of material contamination by mineral oil. In view of developing an adhesive-free process, the potential of ultrasonic compression was investigated in t...

Novel biocomposites were fabricated using preforms of unmodified starch powder and wood pulp fibers. Stacks of preforms were consolidated using thermo-compression (TCM) and ultrasonic compression moldings (UCM). The characterization of the microstructure of the biocomposites showed that TCM enabled a better preservation of the crystallinity of star...

The influence of the soil on the growth of a root system has been largely investigated. By contrast, the aim of this work is to go deep into the details of how the soil may be influenced by the root system. In particular, the root growth process and its potential to improve the soil strength is explored. Even though roots can be seen as fiber-like...

Our project aims at developing a biorefinery integrated in the recycling line of paperboard, where starch would be separated from recovered fibers prior to the production of recycled paperboard. The extracted starch could then be valorized, which requires its characterization. Corrugated board made from recycled fibers was re-dispersed in water and...

Cette étude s'intéresse à la compréhension des mécanismes de déformation d'un assemblage de grains polymériques déformables soumis à de la compression triaxiale. Des essais de compressions triaxiales ont été menés sur des poudres polymériques à l'intérieur même d'un microtomographe à rayons X. Le comportement mécanique macroscopique de la poudre so...

Polymeric deformable granular materials are widely used in industry and the understanding and the modelling of their shaping process is a point of interest. This kind of materials often presents a viscoelasticplastic behaviour and the present study promotes a joint approach between numerical simulations and experiments in order to derive the behavi...

Poster exposed at Powders and Grains 2017, Montpellier (France)

In this study, thermo-compression molding was used to fabricate bulk materials from native starch powder. The objective was to determine the process parameters that enabled the welding of starch granules while preserving their crystallinity. The effects of forming parameters such as temperature, compression stress, and water content on the microstr...

In recent years, cohesive zone models have been formulated and used to numerically simulate the fracture of solid materials. Cohesive zone models presented in the literature involve a ‘jump’ in the displacement field describing crack onset within a predefined interface network corresponding to interfaces between elements of the finite element (FE)...

Since few years, cohesive-zone models have been formulated and used to simulate fracture of solid materials. The cohesive-zone models presented in the literature assume a ‘jump' in the displacement field describing the crack onset within a predefined interface network corresponding to interfaces between elements of the FE mesh. Nevertheless, the ph...

1. Topic The present work deals with solid-solid phase change and is founded on the global and local construction of energy balance during load-unload cycles. Such a construction requires information derived from infrared thermography (IRT) and digital image correlation (DIC). During cyclic tensile tests, the energy fields associated with a CuAlBe...

The paper aims to highlight the advantages of using data supplied by digital image correlation (DIC) and infrared thermography (IRT) to study the thermomechanical behaviour of materials. It describes an experimental procedure for the determination of mechanical energy and heat sources involved locally during a heterogeneous tensile test. This proce...

Le comportement pseudo-élastique des alliages à mémoire de forme (AMF) fait intervenir des mécanismes de changement de phase solide-solide. Afin de mieux comprendre la nature de ces mécanismes, le travail présenté ici s’appuie sur la réalisation d’un bilan d’énergie local qui combine les informations issues de la thermographie infrarouge (TIR) et d...

  The paper aims to highlight the advantages of using data supplied by digital image correlation (DIC) and infrared thermography (IRT) to study the thermomechanical behaviour of materials. It describes an experimental procedure for the determination of mechanical energy and heat sources involved locally during a heterogeneous tensile test. This pro...

By means of tree-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. The sample is composed of polyedric grains with a shape derived from digitalized ballast. The system involves a jammed state separating passive (loading) and active (unloading) states. We show...

We present a three-dimensional discrete-element approach for numerical investigation of wet granular media. This approach relies on basic laws of contact and Coulomb friction enriched by a capillary force law between particles. We show that the latter can be expressed as a simple explicit function of the gap and volume of the liquid bridge connecti...

We investigate the textural properties of cohesive 2D granular packings simulated by means of the molecular dynamics and contact dynamics methods involving simple contact laws with adhesion. We find that, while tensile forces appear naturally in response to external tensile loading, they appear only for a strong adhesion when the applied load is co...

Ballasted tracks have been widely used because of their flexibility from the point of view of construction and maintenance. The deterioration of the railway track under heavy train traffics induces various irregularities in the track mainly as a result of differential settlement. The ballast tamping operation is used in order to restore the initial...

This paper investigates the influence of cohesion on the behavior of 2D granular media simulated by using a molecular dynamics method, involving a simple contact law with adhesion. The study considers an adhesion index which is non intrinsic but significant for interpreting the mechanical effects of applied pressure. A static state system of 4000 p...

We analyze the dynamics of a 3D granular packing composed of particles of irregular polyhedral shape confined inside a rectangular box with a retaining wall sub jected to horizontal harmonic forcing. The simulations are performed by means of the contact dynamics method for a broad set of loading parameters. We explore the vibrational dynamics of th...

We analyze the contact and force networks in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The particle shape effect is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics except for the circular shape of the particles. A surprising observation...

La dynamique des matériaux granulaires vibrés est une question cruciale dans de nombreuses applications, notamment lors de l'opération de bourrage du ballast ferroviaire, qui consiste à rétablir l'aspect géométrique initial des voies. Nous analysons la dynamique d'une couche granulaire confinée en réponse au chargement harmonique d'une paroi en 3D....

The tamping operation on railway ballast is an example where the vibrations are used to restore the initial geometry of the track distorted as a result of ballast settlement. By means of tree-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. The sample is comp...

We perform a detailed analysis of the contact force network in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The effect of particle shape is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics, except for the circular shape of the particles. A...

We perform a detailed analysis of the contact force network in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The effect of particle shape is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics except for the circular shape of the particles. A c...

We perform a detailed analysis of the contact force network in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The effect of particle shape is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics except for the circular shape of the particles. A c...

La physique et la mécanique des matériaux granulaires sont des thèmes de recherche très actifs depuis une décennie. Il existe en effet des applications industrielles nombreuses et variées et en même temps un intérêt fort pour les approches de modélisation et de simulation numérique pour ces matériaux. De façon un peu atypique par rapport à d'autres...

Non renseigné

The ongoing developments in tissue engineering to build lasting, functional cell assemblies highlight the importance of cell-to-cell interactions in the formation of a multicellular structure. Several techniques have been developed over the last years to build 3D cell aggregates and to investigate their cohesivity. Here we introduce a new method: a...

Numerous works show that the mechanical efforts play an important role in the division and the growth of the cell on one hand, and in the organization of cells within a tissue on the other hand. The purpose of this work is to develop a mechanical model to better understand the couplings between biological effects and mechanical effects, this by bei...

By means of two-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. We use irregular polygonal grains allowing for strong variability of solid fraction. The system involves a jammed state separating passive (loading) and active (unloading) states. We show that a...

De nombreux travaux montrent que les efforts mécaniques jouent un rôle important dans la division et la croissance de la cellule d'une part, et dans l'organisation des cellules au sein d'un tissu d'autre part. Le but de ce travail est de développer un modèle mécanique pour mieux cerner les couplages entre effets biologiques et effets mécaniques, ce...

This work investigates the influence of cohesion on the aspect of fracture and crack propagation in 2D rounded cohesive granular packing simulated by the molecular dynamics method involving simple contact laws with adhesion. 2D numerical “Brazilian” test with samples of 8000 identical radius circular particles suggest that the formation of crystall...

This work investigates the influence of cohesion on the aspect of fracture and crack propagation in 2D rounded cohesive granular packing simulated by the molecular dynamics method involving simple contact laws with adhesion. 2D numerical "Brazilian" test with samples of 8000 identical radius circular particles suggest that the formation of crystall...

Calorimetric effects related to the propagation of phase change front in a monocrystalline sample of CuZnAl shape memory alloy were derived from thermographic data analysis. During a load-controlled test, the displacement of the front induces a creep of the sample strongly depending on thermal exchanges with the surroundings. The main role played...

Non renseigné

Non renseigné

Mechanics of Materials has experienced this last decade a considerable expansion. The widening, to non strictly mechanic sciences, of available knowledge and data about the material behaviour has permitted to get a global view of the phenomena accompanying the deformation processes. The use of innovative experimental techniques, the writing of cons...

We propose a behavioral modeling that takes into account the thermomechanical couplings accompanying the phase transition in single-crystal CuZnAl samples. The goal of this model is to put forward the significant role played by the heat diffusion in the propagation mode of the phase change fronts. Numerical simulations showed the existence of such...

Calorimetric effects related to the propagation of a phase change front in a monocrystalline shape memory alloy CuZnAl were derived from thermographic data analysis. At constant load, the displacement of the front induces a creep of the sample strongly depending on thermal exchanges with the surroundings. The main role played by the thermomechanica...

This paper presents, in a synthetic way, several works performed on shape memory alloys (SMAs). Three scales of description are used according to whether one seeks to numerically predict the possible microstructural configurations of phases in equilibrium or the behavior of a mono- and polycrystal of SMA during a phase transition.

In the first part, the theoretical and experimental framework used to present the thermomechanical behaviour of solid materials is briefly recalled. The main feature of the experimental approach relies on the use of thermographical techniques allowing us to deduce, from the thermal data, the distribution of heat sources arising during the mechanica...

Energy balances of a polycrystalline CuZnAl Shape Memory Alloy are performed using infrared and calorimetric techniques. The experiments underline the main role of temperature variations induced by deformation process on the stress–strain curves. A thermodynamic analysis shows variations essentially due to the latent heat of phase change and indica...

In a first part the thermodynamic framework used to introduced the behavioral constitutive equations of solid materials is reminded. Using illustrative examples, the different terms of the energy balance are introduced, specially those due to thermomechanical coupling mechanisms. In a second part the main concepts on multiscale approach are introdu...

Tension-compression tests at different room temperatures and at different strain rates have been performed on Shape Memory Alloys (CuZnAl, NiTi) using a thermomechanical device. The experiments underline the main role of the temperature variations induced by the deformation process on the stress-strain curves. These variations are essentially due t...

One of the obstacles to the industrial use of metal matrix composite materials is the damage they rapidly undergo when they are subjected to cyclic thermal loadings; local thermal stresses of high level can develop, sometimes nearby or over the elastic limit, due to the mismatch of elastic and thermal coefficients between the fibers and the matrix....