Optical interference measurements and fracture mechanics analysis of crack tip craze zones

Döll, W.

doi:10.1007/bfb0024057

Cited by 84 publications

(52 citation statements)

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“…Williams (1984) used a modified Dugdale model to represent a craze at a crack tip and postulated that the crack propagates when a critical opening of this zone is reached, as observed experimentally (Williams, 1984;Döll, 1983). For slightly viscoelastic materials, the experimental craze shape and that calculated from a zone uniformly loaded at the crack tip are similar.…”

Section: Introductionmentioning

confidence: 73%

“…To get some insight in the influence of the various parameters in the craze model presented in Section 3, eight sets of craze parameters have been selected and listed in Table 2. The case number 1 in Table 2 is have been picked on the basis of experimental data (Sternstein and Ongchin, 1969;Döll, 1983) while the values of ⌬ 0 , s c and A c in the kinetic relation MPa√m/sec is taken as reference. For a crack root radius of r t =0.1 mm, such a loading rate is consistent with a displacement rate on the order of 5×10 Ϫ5 m/sec in the remote region of the specimen (about 20 mm from the crack tip).…”

Section: Resultsmentioning

confidence: 99%

“…Williams (1984) postulated that craze breakdown and subsequent crack propagation occurs when a critical craze opening displacement (COD), ⌬ cr , is reached. From fracture experiments on various glassy polymers, (Döll, 1983;Döll and Kön-czöl, 1990) indeed observe such a critical constant craze maximum opening at the crack tip and during crack propagation, for different creep loadings. The experiments also show a craze length that is close to that predicted by Williams (1984).…”

Section: Craze Breakdownmentioning

confidence: 88%

See 2 more Smart Citations

Modeling of the competition between shear yielding and crazing in glassy polymers

Estevez

Tijssens

Giessen

2000

Journal of the Mechanics and Physics of Solids

156

130

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Modeling of the competition between shear yielding and crazing in glassy polymers Estevez, R.; Tijssens, M.G.A.; van der Giessen, E. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractFracture in amorphous glassy polymers involves two mechanisms of localized deformations: shear yielding and crazing. We here investigate the competition between these two mechanisms and its consequence on the material's fracture toughness. The mechanical response of the homogeneous glassy polymer is described by a constitutive law that accounts for its characteristic softening upon yielding and the subsequent progressive orientational strain hardening. The small scale yielding, boundary layer approach is adopted to model the local finite-deformation process in front of a mode I crack. The concept of cohesive surfaces is used to represent crazes and the traction-separation law incorporates craze initiation, widening and breakdown leading to the creation of a microcrack. Depending on the craze initiation sensitivity of the material, crazing nucleates at the crack tip during the elastic regime or ahead of the crack. As the crazes extend, plasticity develops until an unstable crack propagation takes place when craze fibrils start to break down. Thus, the critical width of a craze appears to be a key feature in the toughness of glassy polymers. Moreover, the opening rate of the craze governs the competition between shear yielding and brittle failure by crazing.

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Section: Introductionmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Section: Craze Breakdownmentioning

confidence: 88%

See 1 more Smart Citation

Modeling of the competition between shear yielding and crazing in glassy polymers

Estevez

Tijssens

Giessen

2000

Journal of the Mechanics and Physics of Solids

156

130

View full text Add to dashboard Cite

show abstract

“…We also impose condition (3.4) requiring that the total crack opening, d, must always be less than the critical crack opening, d c , for all applied opening rates otherwise the traction must drop to zero. This is a somewhat arbitrary assumption of the model, which is not necessarily valid for all failure mechanisms; however it does appear to be valid for a crazing failure mechanism (Doll, 1983;Kramer and Berger, 1990). This form of the cohesive zone law is similar to that used by Freund and Lee (1990) to study dynamic viscoplastic fracture within the context of a strip yield model.…”

Section: Fracture Process Constitutive Lawmentioning

confidence: 87%

Crack velocity dependent toughness in rate dependent materials

Landis

Pardoen

Hutchinson

2000

Mechanics of Materials

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Mode I, quasi-static, steady-state crack growth is analyzed for rate dependent materials under plane strain conditions in small scale yielding. The solid is characterized by an elastic±viscoplastic constitutive law and the plane ahead of the crack tip is embedded with a rate dependent fracture process zone. The macroscopic work of fracture of the material is computed as a function of the crack velocity and the parameters characterizing the fracture process zone and the solid. With increasing crack velocity a competition exists between the strain rate hardening of the solid, which causes elevated tractions ahead of the crack tip that tend to drive crack propagation, and the rate strengthening of the fracture process zone which tends to resist fracture. Results for material parameters characteristic of polymers show that the toughness of the material can either increase or decrease with increasing crack velocity. To motivate the model, the cohesive zone parameters are discussed in terms of failure mechanisms such as crazing and void growth ahead of the crack tip. The toughness of rubber modi®ed epoxies is explained by employing the fracture model along with micromechanical void cell calculations. Ó

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“…PMMA fails by crazing (Döll 1983;SaadGouider et al 2006) and its failure mechanism can be determined from inverse analysis (Elices et al 2002) or crack tip field analysis (Réthoré and Estevez 2013). However, a brittle cracking model was used for simulating this matrix failure in the current study.…”

Section: Damage Models and Materials Definitionmentioning

confidence: 97%

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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Optical interference measurements and fracture mechanics analysis of crack tip craze zones

Cited by 84 publications

References 83 publications

Modeling of the competition between shear yielding and crazing in glassy polymers

Modeling of the competition between shear yielding and crazing in glassy polymers

Crack velocity dependent toughness in rate dependent materials

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

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