Transition from slow to fast crack propagation in PMMA

Döll, W.; Weidmann, G. W.

doi:10.1007/bf00752104

Cited by 32 publications

(10 citation statements)

References 8 publications

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“…These patterns were not smooth undulations along the fracture surface, but were discrete bands of jagged cliff-like structures [23]. A similar observation was made in earlier investigations by Doll and Weidmann [24], Kusy and Turner [25], and Doyle [26]. Further investigation by Sharon et al [17] confirmed that the surface structure was a result of micro-branch formation.…”

Section: Introductionsupporting

confidence: 69%

Dynamic crack bifurcation in PMMA

Murphy

Ali

2006

Engineering Fracture Mechanics

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Publication informationEngineering Fracture Mechanics, 73 (16): 2569-2587Publisher Elsevier Item record/more information http://hdl.handle.net/10197/4908 Publisher's statementThis is the author's version of a work that was accepted for publication in Engineering Fracture Mechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Engineering Fracture Mechanics (73, 16, (2006) AbstractAn investigation of the branching characteristics of small PMMA single edge notched tensile (SENT) specimens is presented. The influence of notch depth and specimen thickness was examined and it was found that branching only occurred for thicker specimens and very short notch depths. The location at which successful branching occurred was very consistent for a given notch depth. Subsequently, however, a statistical variation of branching patterns was observed. A series of simulations was then performed to provide further insight into these tests and in particular to examine the evolution of the fracture process region ahead of the running crack. A finite volume / cohesive zone formulation was used to model micro-crack nucleation and dynamic interaction in the process zone. The cohesive strength and fracture resistance were estimated from unnotched tensile tests and the application of LEFM to the notch test data. Even though a very simple criterion was used to govern the insertion and subsequent behaviour of the cohesive surfaces in the model, many of the experimental observations were reproduced, including high frequency oscillations in crack velocity, the substantial increase in the fracture surface area due to the formation of subsurface microcracks, and location at which successful branching took place.

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Section: Introductionsupporting

confidence: 69%

Dynamic crack bifurcation in PMMA

Murphy

Ali

2006

Engineering Fracture Mechanics

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“…Maugis [25] has attributed the decrease in G c after point 'A' has been reached to a significant reduction in the loss modulus, occurring when the crack propagates sufficiently fast that the material tends to behave in a more elastic fashion. On the other hand, Williams [14] has speculated that, for poly(methyl methacrylate), the decrease in G c reported to occur between 1.5 m/minute and 6 m/minute (see [26][27][28][29]) corresponded to the case where the heat generated at the crack tip is not dissipated, resulting in a softening of the polymer and a decrease in the fracture energy. Notwithstanding, other workers [26] have suggested that the decrease in G c is associated with a tanδ R peak, and that this tanδ R peak is governed by the β process, i.e.…”

Section: The Transition From 'Region I' To 'Region Iii' Behaviourmentioning

confidence: 99%

Crack Growth of Structural Adhesive Joints in Humid Environments

Korenberg¹,

Kinloch²,

Watts

2004

The Journal of Adhesion

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The adhesive fracture energy, G c , of aluminium-alloy and steel joints, bonded with a rubbertoughened epoxy adhesive, has been measured using monotonically-loaded tests. Such tests have been conducted at different levels of relative humidity and two surface pretreatments have been employed for the substrates prior to bonding: a simple grit-blast and degrease ('GBD') pretreatment or a silane primer ('GBS') pretreatment. When G c was plotted against the crack velocity, three regions of fracture behaviour could be distinguished. At low rates of displacement the crack grew in a stable manner, visually along the interface, and relatively low crack velocities could be readily measured. This was termed 'Region I' and here the value of the adhesive fracture energy was relatively low and decreased steadily as the relative humidity was increased. On the other hand, at relatively high rates of displacement the crack grew in a stick-slip manner mainly cohesively in the adhesive layer at approximately 20 km/minute. This was termed 'Region III', and here the value of G c was relatively high and independent of the relative humidity. In this region the crack was considered to grow faster than the water molecules were able to reach the crack tip, which explains the independence of G c upon the test environment. In between 'Region I' and 'Region III', a transition region was observed which was designated as 'Region II'. The major effect of the 'GBS' pretreatment, compared to the 'GBD' pretreatment, was to increase the value of G c both in 'Regions I and III', although the presence of the silane primer had the greater effect in 'Region I'. INTRODUCTIONThe use of structural adhesives offers many advantages when compared with other more traditional joining methods such as welding, riveting and mechanical fasteners [1]. However, as with any technology, there are some potential disadvantages associated with the use of adhesives.In particular, adhesive joints may suffer environmental attack when exposed to relatively hot and humid environments. The development of a sound accelerated-ageing test method to assess the susceptibility of an adhesive 'system' (i.e. the adhesive/primer (if any)/substrate and substrate surface pretreatment in combination) to such attack would represent a significant advance, especially if such tests could be completed in a relatively short time-scale [2].The aim of a sound and meaningful accelerated ageing test must be to accelerate the mechanisms of attack seen during the service-life of the bonded joint, and not to induce misleading and irrelevant mechanisms. For example, it is well known that to accelerate the rate of environmental attack it is not possible simply to raise the temperature of the environment, since unrealistically high test temperatures will indeed change the mechanisms of attack. One method of accelerating the rate of attack which has recently been explored in detail by Kinloch and coworkers (e.g. [3]) has been the use of cyclic-fatigue tests, using a fracture-mechanics approach, conducte...

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“…• that cracks in amorphous brittle materials such as glass or Plexiglas pass almost instantaneously from quasi-static motion to motion at about 10% of the Rayleigh wave speed (DÖLL AND WEIDMANN 1976;TAKAHASHI, MATSUSHIGE, AND SAKURADA 1984) .…”

Section: Introductionmentioning

confidence: 99%

Origin of crack tip instabilities

Marder

Gross

1995

Journal of the Mechanics and Physics of Solids

280

247

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This paper demonstrates that rapid fracture of ideal brittle lattices naturally involves phenomena long seen in experiment, but which have been hard to understand from a continuum point of view. These idealized models do not mimic realistic microstructure, but can be solved exactly and understood completely. First it is shown that constant velocity crack solutions do not exist at all for a range of velocities starting at zero and ranging up to about one quarter of the shear wave speed. Next it is shown that above this speed cracks are by and large linearly stable, but that at sufficiently high velocity they become unstable with respect to a nonlinear micro-cracking instability. The way this instability works itself out is related to the scenario known as intermittency, and the basic time scale which governs it is the inverse of the amount of dissipation in the model. Finally, we compare the theoretical framework with some new experiments in Plexiglas, and show that all qualitative features of the theory are mirrored in our experimental results.

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Transition from slow to fast crack propagation in PMMA

Cited by 32 publications

References 8 publications

Dynamic crack bifurcation in PMMA

Dynamic crack bifurcation in PMMA

Crack Growth of Structural Adhesive Joints in Humid Environments

Origin of crack tip instabilities

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