Publications (19)38.29 Total impact
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Article: Intermittent stick-slip dynamics during the peeling of an adhesive tape from a roller.
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ABSTRACT: We study experimentally the fracture dynamics during the peeling at a constant velocity of a roller adhesive tape mounted on a freely rotating pulley. Thanks to a high speed camera, we measure, in an intermediate range of peeling velocities, high frequency oscillations between phases of slow and rapid propagation of the peeling fracture. This so-called stick-slip regime is well known as the consequence of a decreasing fracture energy of the adhesive in a certain range of peeling velocity coupled to the elasticity of the peeled tape. Simultaneously with stick slip, we observe low frequency oscillations of the adhesive roller angular velocity which are the consequence of a pendular instability of the roller submitted to the peeling force. The stick-slip dynamics is shown to become intermittent due to these slow pendular oscillations which produce a quasistatic oscillation of the peeling angle while keeping constant the peeling fracture velocity (averaged over each stick-slip cycle). The observed correlation between the mean peeling angle and the stick-slip amplitude questions the validity of the usually admitted independence with the peeling angle of the fracture energy of adhesives.Physical Review E 02/2013; 87(2-1):022601. · 2.26 Impact Factor -
Article: Attractive and repulsive cracks in a heterogeneous material
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ABSTRACT: We study experimentally the paths of an assembly of cracks growing in interaction in a heterogeneous two-dimensional elastic brittle material submitted to uniaxial stress. For a given initial crack assembly geometry, we observe two types of crack path. The first one corresponds to a repulsion followed by an attraction on one end of the crack and a tip-to-tip attraction on the other end. The second one corresponds to a pure attraction. Only one of the crack path types is observed in a given sample. Thus, selection between the two types appears as a statistical collective process.Journal of Statistical Mechanics Theory and Experiment 10/2008; 2008(10):P10022. · 1.73 Impact Factor -
Article: Surface oscillations and slow crack growth controlled by creep dynamics of necking instability in a glassy film
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ABSTRACT: We study experimentally the slow growth of a single crack in a glassy film of polycarbonate submitted to uniaxial and constant imposed load. Flame-shaped macroscopic zones of plastic deformation appear at the tips of the crack and the formation of these plastic zones involves a necking instability. In order to understand the crack growth dynamics, we study first the growth dynamics of the plastic zones alone, i.e. without crack, at constant imposed load. We find that the growth velocity of the neck can be very well described by the same Eyring’s factor than the one describing the creep flow of polycarbonate. In addition, we discover that a surface oscillation with a very large wavelength to amplitude ratio occurs during the neck propagation, and that both wavelength and amplitude are proportional to the film thickness. Finally, we succeed to model analytically the dependance of the instantaneous crack velocity with experimental variables using Dugdale-Barenblatt static description of crack tip plastic zones associated to an Eyring’s law and an empirical dependence with the crack length that may come from a residual elastic field.The European Physical Journal E 10/2008; · 1.94 Impact Factor -
Article: Dynamical law for slow crack growth in polycarbonate films.
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ABSTRACT: We study experimentally the slow growth of a single crack in polycarbonate films submitted to uniaxial and constant imposed stress. For this viscoplastic material, we uncover a dynamical law that describes the dependence of the instantaneous crack velocity with experimental parameters. The law involves a Dugdale-Barenblatt static description of crack tip plastic zones associated to an Eyring's law and an empirical dependence with the crack length that may come from a residual elastic field.Physical Review Letters 12/2007; 99(20):205502. · 7.37 Impact Factor -
Article: Statistical properties of microcracking in polyurethane foams under tensile test, influence of temperature and density
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ABSTRACT: We report tensile failure experiments on polyurethane (PU) foams. Experiments have been performed by imposing a constant strain rate. We work on heterogeneous materials for whom the failure does not occur suddenly and can develop as a multistep process through a succession of microcracks that end at pores. The acoustic energy and the waiting times between acoustic events follow power-law distributions. This remains true while the foam density is varied. However, experiments at low temperatures (PU foams more brittle) have not yielded power-laws for the waiting times. The cumulative acoustic energy has no power law divergence at the proximity of the failure point which is qualitatively in agreement with other experiments done at imposed strain. We notice a plateau in cumulative acoustic energy that seems to occur when a single crack starts to propagate.International Journal of Fracture 07/2007; · 1.49 Impact Factor -
Article: Statistics of fracture surfaces.
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ABSTRACT: We analyze the statistical distribution function for the height fluctuations of brittle fracture surfaces using extensive experimental data sampled on widely different materials and geometries. We compare a direct measurement of the distribution to an analysis based on the structure functions. For length scales delta larger than a characteristic scale Lambda that corresponds to a material heterogeneity size, we find that the distribution of the height increments Deltah=h(x+delta)-h(x) is Gaussian and monoaffine, i.e., the scaling of the standard deviation sigma is proportional to delta(zeta) with a unique roughness exponent. Below the scale Lambda we observe a deviation from a Gaussian distribution and a monoaffine behavior. We discuss for the latter, the relevance of a multiaffine analysis and the influences of the discreteness resulting from material microstructures or experimental sampling.Physical Review E 02/2007; 75(1 Pt 2):016104. · 2.26 Impact Factor -
Article: Subcritical crack growth in fibrous materials
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ABSTRACT: We present experiments on the slow growth of a single crack in a fax paper sheet submitted to a constant force $F$. We find that statistically averaged crack growth curves can be described by only two parameters : the mean rupture time $\tau$ and a characteristic growth length $\zeta$. We propose a model based on a thermally activated rupture process that takes into account the microstructure of cellulose fibers. The model is able to reproduce the shape of the growth curve, the dependence of $\zeta$ on $F$ as well as the effect of temperature on the rupture time $\tau$. We find that the length scale at which rupture occurs in this model is consistently close to the diameter of cellulose microfibrils.EPL (Europhysics Letters) 01/2007; · 2.17 Impact Factor -
Article: Super-Arrhenius dynamics for sub-critical crack growth in two-dimensional disordered brittle media
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ABSTRACT: Taking into account stress fluctuations due to thermal noise, we study thermally activated irreversible crack growth in disordered media. The influence of material disorder on sub-critical growth of a single crack in two-dimensional brittle elastic material is described through the introduction of a gaussian rupture threshold distribution. We derive analytical predictions for crack growth velocity and material lifetime in agreement with direct numerical calculations. It is claimed that crack growth process is inhibited by disorder: velocity decreases and lifetime increases with disorder. More precisely, lifetime is shown to follow a super-Arrhenius law, with an effective temperature $\theta-\theta_d$, where $\theta$ is related to the thermodynamical temperature and $\theta_d$ to the disorder variance.EPL (Europhysics Letters) 01/2007; · 2.17 Impact Factor -
Article: Slow crack growth in polycarbonate films
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ABSTRACT: We study experimentally the slow growth of a single crack in polycarbonate films submitted to uniaxial and constant imposed stress. The specificity of fracture in polycarbonate films is the appearance of flame shaped macroscopic process zones at the tips of the crack. Supported by an experimental study of the mechanical properties of polycarbonate films, an analysis of the stress dependence of the mean ratio between the process zone and crack lengths, during the crack growth, show a quantitative agreement with the Dugdale-Barenblatt model of the plastic process zone. We find that the fracture growth curves obey strong scaling properties that lead to a well defined growth master curve.EPL (Europhysics Letters) 01/2007; · 2.17 Impact Factor -
Article: The cooperative effect of load and disorder in thermally activated rupture of a two-dimensional random fuse network
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ABSTRACT: A random fuse network, or equivalently a two-dimensional spring network with quenched disorder, is subjected to a constant load and thermal noise, and studied by means of numerical simulations. Rupture is thermally activated and the lifetime follows an Arrhenius law where the energy barrier is reduced by disorder. Due to the non-homogeneous distribution of forces from the stress concentration at microcrack tips, spatial correlations between rupture events appear, but they do not affect the energy barrier's dependence on the disorder; they affect only the coupling between the disorder and the applied load.07/2006; -
Article: Fracture surfaces as multiscaling graphs.
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ABSTRACT: Fracture paths in quasi-two-dimensional (2D) media (e.g., thin layers of materials or paper) are analyzed as self-affine graphs h(x) of height h as a function of length x. We show that these are multiscaling, in the sense that nth order moments of the height fluctuations across any distance l scale with a characteristic exponent that depends nonlinearly on the order of the moment. Having demonstrated this, one rules out a widely held conjecture that fracture in 2D belongs to the universality class of directed polymers in random media. In fact, 2D fracture does not belong to any of the known kinetic roughening models. The presence of multiscaling offers a stringent test for any theoretical model; we show that a recently introduced model of quasistatic fracture passes this test.Physical Review Letters 03/2006; 96(5):055509. · 7.37 Impact Factor -
Article: Subcritical statistics in rupture of fibrous materials: experiments and model.
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ABSTRACT: We study experimentally the slow growth of a single crack in a fibrous material and observe stepwise growth dynamics. We model the material as a lattice where the crack is pinned by elastic traps and grows due to thermally activated stress fluctuations. In agreement with experimental data we find that the distribution of step sizes follows subcritical point statistics with a power law (exponent 3/2) and a stress-dependent exponential cutoff diverging at the critical rupture threshold.Physical Review Letters 09/2004; 93(9):095505. · 7.37 Impact Factor -
Article: Influence de la dynamique de la rupture sur l'exposant de rugosité dans les ractures 1D
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ABSTRACT: Nous déterminons l'exposant de rugosité de fractures en utilisant plusieurs estimateurs de lois d'échelle existant dans la littérature dont un récent : les coefficients dominants [1]. A partir d'un large jeu de réalisations d'une expérience de rupture d'une feuille de papier (102 fronts), nous comparons les exposants estimés dans deux régimes de croissance différents. Les résultats montrent un écart significatif à l'invariance d'échelle et une différence significative entre la valeur des exposants estimés dans le régime de croissance lente (sous-critique) et le régime de croissance rapide.21° Colloque GRETSI, 2007 ; p. 1081-1084. -
Article: Slow crack growth : models and experiments
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ABSTRACT: The properties of slow crack growth in brittle materials are analyzed both theoretically and experimentally. We propose a model based on a thermally activated rupture process. Considering a 2D spring network submitted to an external load and to thermal noise, we show that a preexisting crack in the network may slowly grow because of stress fluctuations. An analytical solution is found for the evolution of the crack length as a function of time, the time to rupture and the statistics of the crack jumps. These theoretical predictions are verified by studying experimentally the subcritical growth of a single crack in thin sheets of paper. A good agreement between the theoretical predictions and the experimental results is found. In particular, our model suggests that the statistical stress fluctuations trigger rupture events at a nanometric scale corresponding to the diameter of cellulose microfibrils. -
Article: Discrepancy between sub-critical and fast rupture roughness : a cumulant analysis
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ABSTRACT: Rough crack fronts in a sheet of paper, obtained during a creep experiment, do not follow true scaling laws. Local roughness exponents are estimated using the first order cumulant, a quantity recently introduced in the turbulence literature. Using a large data set (102 fronts), we find a significant difference in local roughness between the slow (sub-critical) and the fast growth regime. -
Article: Imaging the stick-slip peeling of an adhesive tape under a constant load
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ABSTRACT: Using a high speed camera, we study the peeling dynamics of an adhesive tape under a constant load with a special focus on the so-called stick-slip regime of the peeling. It is the first time that the very fast motion of the peeling point is imaged. The speed of the camera, up to $16000$ fps, allows us to observe and quantify the details of the peeling point motion during the stick and slip phases: stick and slip velocities, durations and amplitudes. First, in contrast with previous observations, the stick-slip regime appears to be only transient in the force controlled peeling. Additionally, we discover that the stick and slip phases have similar durations and that at high mean peeling velocity, the slip phase actually lasts longer than the stick phase. Depending on the mean peeling velocity, we also observe that the velocity change between stick and slip phase ranges from a rather sudden to a smooth transition. These new observations can help to discriminate between the various assumptions used in theoretical models for describing the complex peeling of an adhesive tape. The present imaging technique opens the door for an extensive study of the velocity controlled stick-slip peeling of an adhesive tape that will allow to understand the statistical complexity of the stick-slip in a stationary case. -
Article: Thermal activation of rupture and slow crack growth in a model of homogenous brittle materials
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ABSTRACT: Slow crack growth in a model of homogenous brittle elastic material is described as a thermal activation process where stress fluctuations allow to overcome a breaking threshold through a series of irreversible steps. We study the case of a single crack in a flat sheet for which analytical predictions can be made, and compare them with results from the equivalent problem of a 2D spring network. Good statistical agreement is obtained for the crack growth profile and final rupture time. The specific scaling of the energy barrier with stress intensity factor appears as a consequence of irreversibility. In addition, the model brings out a characteristic growth length whose physical meaning could be tested experimentally. -
Article: Failure time, critical behaviour and activation processes in crack formation
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ABSTRACT: In this seminar we will review several experimental and theoretical aspects of two very important problems of material failure: crack precursors and crack prediction. We will summarize the results of several experiments and numerical simulations that we have performed in order to give new insight on these two important problems. Specifically the acoustic emission of fracture precursors, and the failure time of samples made of heterogeneous materials (wood, fiberglass) are studied as a function of the load features and geometry -
Article: Physics of sub-critical crack growth in a fibrous material: experiments and model
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ABSTRACT: We are interested in slow rupture processes observed when a material is submitted to a constant load below a critical rupture threshold. It is well known that the delay time (or lifetime) of the material before complete macroscopic rupture strongly depends on the applied stress. Thermodynamics has slowly emerged as a possible framework to describe delayed rupture of materials since early experiments have shown temperature dependence of lifetime with an Arrhenius law. On the other hand, efforts are made to describe slow rupture dynamics from rheological properties of the material such as viscoelasticity and plasticity. To shed light on this problem, it is important to compare experiments and models to distinguish between the different theoretical descriptions. For this purpose, we have studied experimentally the slow growth of a single crack in a fibrous material made of fax paper. Specifically, we have observed that the crack grows by steps of various sizes whose distribution is rather complex and evolves as a function of the crack length. In spite of this complexity, a statistical average of the growth dynamics reveals a very simple behaviour. We show that a model of thermally activated dynamics is able to reproduce many experimental observations. In particular, we show that the average dynamics is in good agreement with the experimental data. In addition, we find that the distribution of step sizes follows sub-critical point statistics with a power law and a stress-dependent exponential cut-off diverging at the critical rupture threshold. The exponent of the power law predicted by the model (3/2) seems to be slightly too large. Leaving the exponent as a free parameter gives a value 1.23+/-0.1. We stress that the material heterogeneity appears in the model only as a characteristic mesoscopic length scale. The fact that a simple model of thermally activated crack dynamics is able to reproduce with a good accuracy our experimental findings may open new perspectives in the description of slow rupture dynamics.
Top co-authors
Top Journals
Institutions
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2004–2013
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French National Centre for Scientific Research
Lyon, Rhone-Alpes, France
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2007–2008
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Ecole normale supérieure de Lyon
Lyon, Rhone-Alpes, France
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2006
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Weizmann Institute of Science
- Department of Chemical Physics
Israel
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