Micromechanics of fracture under static and fatigue loading: Optical interferometry of crack tip craze zones

Döll, W.; Könczöl, László

doi:10.1007/bfb0018021

Cited by 34 publications

(37 citation statements)

References 128 publications

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“…The related energy release rate is derived from Equation (5) and compared to the experimental data. The simulations predict a craze length about 30 µm which is comparable to the measures reported in [5,6]. By using the maximum principal stress σ 1 cr = 55 MPa for craze initiation and a critical thickness Δ cr n = 3 µm for the condition of craze fibrils breakdown, the experimental data reported in Figure 2b are used to calibrate the parameters involved in the craze thickening rate (Δ 0 , σ c and A c ) in Equation (1).…”

Section: Calibrationsupporting

confidence: 64%

“…The measure of the molecular weight by size exclusion chromatography results in M n = 864 kg/mol and M w = 1843 kg/mol. Döll, and Döll and Könczöl [5,6] observed and reported an influence of the molecular weight and related chain length on the development of a stable craze in amorphous polymers. For PMMA, a critical value of about M n cr = 200 kg/mol, below which no stable crazes are observed, is evidenced.…”

Section: Experimental Calibrationmentioning

confidence: 99%

“…The craze fibrils thicken up to a critical value Δ cr n for which the fibrils break down which corresponds to the nucleation of a crack locally. The maximum thickness Δ cr n is also a material parameter which can fairly be taken constant in the case of PMMA, at a fixed temperature [5,6].…”

Section: Cohesive Zone Formulation For Crazingmentioning

confidence: 99%

“…The purpose is to define a complete protocol to calibrate the parameters involved in this theoretical description. Since the condition for craze breakdown has been extensively investigated by interferometry with data available for instance in [5,6], we borrow from these studies a condition based on a critical craze thickness for the nucleation of a crack. Therefore, the present study focuses on the characterisation of the first two stages of crazing: initiation and thickening.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cohesive Zone Description and Quantitative Analysis of Glassy Polymer Fracture

Saad¹,

Estevez²,

Olagnon³

et al. 2006

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Modélisation par zone cohésive et étude expérimentale de la rupture des polymères vitreux -Le craquelage est décrit à l'aide d'une zone cohésive qui prend en compte l'amorçage, l'élargissement des surfaces des craquelures jusqu'à la rupture des fibrilles qui correspond à la création d'une fissure localement. Une calibration des paramètres de la zone cohésive est présentée pour le PMMA (Polymethyl methacrylate). Nous montrons qu'il est nécessaire de décrire le craquelage à l'aide d'une zone cohésive viscoplastique pour rendre compte des effets de la vitesse de chargement sur la ténacité du matériau, qui dépend des conditions de sollicitation. Abstract -Cohesive Zone Description and Quantitative Analysis of Glassy Polymer Fracture -

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Section: Calibrationsupporting

confidence: 64%

Section: Experimental Calibrationmentioning

confidence: 99%

Section: Cohesive Zone Formulation For Crazingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cohesive Zone Description and Quantitative Analysis of Glassy Polymer Fracture

Saad¹,

Estevez²,

Olagnon³

et al. 2006

Oil & Gas Science and Technology - Rev. IFP

View full text Add to dashboard Cite

show abstract

“…Only flexural tests were performed in the present work due to a limitation in the material supply. As already mentioned, the value of the flexural strength is approximately 1.5-2.1 times higher than that of the tensile strength (Wypych 2016 (Döll 1983;Döll and Könczöl 1990)). Therefore it is concluded that using the failure strength of the polymer as the crack initiation stress is appropriate.…”

Section: Elasticmentioning

confidence: 77%

Development of an image-based numerical model for predicting the microstructure–property relationship in alumina trihydrate (ATH) filled poly(methyl methacrylate) (PMMA)

2018

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Particulate composites are found in a wide range of applications. Their heterogeneous microstructure affects their bulk behavior and structural performance, however tools for predicting this important structure-property relationship are still lacking. In this study, a numerical method that can provide predictions of the mechanical response of a particulate polymeric matrix composite as a function of volume fraction and particle mean diameter is presented. The work is derived for an alumina trihydrate filled poly(methyl methacrylate) but the methodology is generic and can be used for any particulate composite. Representative Volume elements are determined through images obtained from scanning electron microscopy. The model takes into account the possibility of failure through interface debonding as well as cracks through the matrix. The model predictions for the modulus and fracture strength of the composites are validated through independent experiments on the composite. The numerical results are also used to qualitatively explain the trends measured regarding the fracture toughness of the composites. Compared to other literature on particulate composites, our study is the first to report accurate stress-strain distributions as well as fracture predictions whilst all the necessary model parameters defining the failure criteria are all derived through independent experiments. This paves R. Zhang · J. Y. S. Li-Mayer · M. N. Charalambides (B) Department of Mechanical Engineering, Imperial College London, South Kensington, London SW7 2AZ, UK e-mail: m.charalambides@imperial.ac.uk the way for a relatively simple methodology for determining structure-property relationships in composites design, enabling smarter material utilization and optimal mechanical properties.

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Yield and Crazing in Polymers

O’Connell

McKenna

2004

Encyclopedia of Polymer Science and Technology

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The present article discusses yield and crazing in polymeric materials. After introducing the definitions of stress and strain states, we present a brief summary of the general stress–strain responses for polymers under uniaxial tensile and compressive loading. We introduce the various regimes of behavior, from almost linear elastic through the nonlinear response to rubber‐like behavior. We also include the concepts of necking and cold drawing and the Considère construction for determining whether a material will undergo either of these processes. The history of the development of yield criteria and models is then examined in some details. Yield criteria, which may be considered as macroscopic criteria relating the applied stress state to a critical value for yielding, are first discussed and the modifications for pressure dependence introduced. These criteria, while useful from an engineering point of view in that they offer a method to estimate the likelihood of failure for a given loading situation, provide no insight into the microscopic or molecular mechanisms that give rise to yield. Early theories of yield (eg adiabatic heating and strain induced dilatation), though now considered incorrect, are mentioned in their historical context. A number of models are then presented which consider yield as an activated process. In these models, resistance to yielding is considered as being due to inter‐ and/or intramolecular forces. Application of stress (or the associated strain) affects the energy landscape of the material such that the energy barrier for this resistance is reduced and yield can occur. More complex models are then presented which address not only the yield of the material but the subsequent strain‐softening and strain‐hardening events that are observed. We conclude the section on yield by some brief, general observations on dislocation plasticity, the ultimate shear strength, dilatometry and calorimetry, computer modeling, and finally some discussion of yield in semi‐crystalline materials. The second section of the current chapter discusses the phenomenon of crazing. Crazing is a microscopically localized phenomenon, which involves a large degree of localized plastic deformation. Yet, crazing is generally the precursor to macroscopically brittle failure at low craze densities. An overview of craze morphology is first given to familiarize the reader with the main structural features of crazes. The development of a craze can be conveniently subdivided into three stages—initiation, growth, and failure—and each stage is examined separately. As with the yield section, craze initiation is examined in an historical context and the development of theories considering, variously, a critical cavitation stress, a critical strain, or the presence of inherent microvoids which can grow under the applied local stress or strain are discussed. There is general consensus on the mechanisms for craze growth. Craze tip advance is thought to occur by the Taylor meniscus instability mechanism, while craze thickening is due to the drawing in of material from the bulk–fibril interface. Both these mechanisms are presented and the dependence on, for example, molecular weight and cross‐link density discussed. Craze failure is examined in terms of either fibril failure or failure at the bulk–fibril interface. The section is completed by considering other factors for craze formation and failure (effect of cross‐tie fibrils, environmental‐stress cracking, and fatigue failure).

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Micromechanics of fracture under static and fatigue loading: Optical interferometry of crack tip craze zones

Cited by 34 publications

References 128 publications

Cohesive Zone Description and Quantitative Analysis of Glassy Polymer Fracture

Cohesive Zone Description and Quantitative Analysis of Glassy Polymer Fracture

Development of an image-based numerical model for predicting the microstructure–property relationship in alumina trihydrate (ATH) filled poly(methyl methacrylate) (PMMA)

Yield and Crazing in Polymers

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