Multiple kinks in lamellar linear polyethylene

Rose, W.; Meurer, C.

doi:10.1007/bf00542731

Cited by 9 publications

(4 citation statements)

References 14 publications

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“…The slanted cracks intersect at an angle between 50 and 55° with respect to the loading direction. As has been documented by various authors, shear banding can exist alongside crazing in many semicrystalline polymers such as HDPE, atactic PS or PP under compression . Although the tests reported in this study were performed under tension, it is noted that the observation of the zone occurs very close to the notch surface.…”

Section: Discussionmentioning

confidence: 52%

“…As has been documented by various authors, shear banding can exist alongside crazing in many semicrystalline polymers such as HDPE, atactic PS or PP under compression. [72][73][74][75][76][77][78] Although the tests reported in this study were performed under tension, it is noted that the observation of the zone occurs very close to the notch surface. As has been introduced at the beginning, Ferreiro et al have reported fi nding fi ne parallel shear/slip bands in PA6 which cross the spherulites and run uniformly through the whole sample surface and intersect at 52° to the direction of the tensile axis.…”

Section: Discussionmentioning

confidence: 99%

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3D Damage Micromechanisms in Polyamide 6 Ahead of a Severe Notch Studied byIn SituSynchrotron Laminography

Cheng

Laiarinandrasana

Helfen

et al. 2016

Macromol. Chem. Phys.

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Micro‐damage mechanisms in a semicrystalline polyamide 6 polymer are characterized by in situ synchrotron radiation computed laminography (SRCL) using compact‐tension like specimens with a notch root radius of 0.25 mm. SRCL allows the quantification of cavity nucleation, growth, and coalescence in flat 2 mm thick notched specimens with a micrometer resolution in 3D (under conditions of severe stress triaxiality) during the in situ loading. The maximum damage occurred at mid‐thickness and was located at a small distance ≈ 200 µm from the notch root. It is shown that damage is distributed in distinct zones, which can be linked to different stress triaxiality states. Penny‐shaped cracks are found after some loadings and their diameters are a function of the distance to the notch root. In a layer of about 33 µm no damage was found. In the adjacent 128 µm layer, penny‐shaped cracks are found with diameters of the order of average spherulite sizes (4–6 µm). In the next region, 30–45 µm long cracks are found corresponding to several average spherulite diameters. During propagation, tunnel‐like cracks are formed ahead of the main crack. Finally, crack initiation location is found to be largely dependent on the roughness of the machined notch surface by comparing two samples with the same loading conditions.

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Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

3D Damage Micromechanisms in Polyamide 6 Ahead of a Severe Notch Studied byIn SituSynchrotron Laminography

Cheng

Laiarinandrasana

Helfen

et al. 2016

Macromol. Chem. Phys.

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“…As the strain increases further, these undulations grow and transform into bigger folds or angular kinks that may eventually form a chevron morphology [16]. Such morphology, originating from microbuckling instability, was also observed at the nano-and micrometer scale in block copolymers with a well-oriented lamellar morphology [16][17][18][19][20][21][22][23] and in semicrystalline polymers, either unoriented [4,9,[24][25][26][27][28][29][30][31] or oriented [13,24,25,29,32]. Krumova et al [9] argued that microbuckling, resulting in a chevron-like morphology, is a common deformation mode that can operate not only in materials with a well-ordered layered structure (e.g., layered rocks, oriented block copolymers with a lamellar structure, or oriented semicrystalline polymers) but also in ordinary ones-i.e., generally unoriented or only slightly oriented semicrystalline polymers.…”

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 86%

Microbuckling Instability and the Second Yield during the Deformation of Semicrystalline Polyethylene

Bartczak

Vozniak

2020

Polymers

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Deformation instabilities, such as microbuckling or lamellar fragmentation due to slip localization, play a very important role in the deformation of semicrystalline polymers, although it still not well explored. Such instabilities often appear necessary to modify the deformation path and facilitate strain accommodation in an energy-minimizing manner. In this work, microbuckling instability was investigated using partially oriented, injection-molded (IM) samples of high-density polyethylene, deformed by a plane-strain compression. Deformed samples were probed by SEM, X-ray (small- and wide-angle X-ray scattering: SAXS, WAXS), and differential scanning calorimetry (DSC). It was found that microbuckling instability, followed quickly by the formation of lamellar kinks, occurred in high-density polyethylene (HDPE) at a true strain of about e = 0.3–0.4, mainly in those lamellar stacks which were initially oriented parallel to the compression direction. This phenomenon was observed with scanning electron microscopy, especially in the oriented skin layers of IM specimens, where a chevron morphology resulting from lamellae microbuckling/kinking was evidenced. Macroscopically, this instability manifested as the so-called “second macroscopic yield” in the form of a hump in the true stress–true strain curve. Microbuckling instability can have a profound effect on the subsequent stages of the deformation process, as well as the resulting structure. This is particularly important in deforming well-oriented lamellar structures—e.g., in drawing pre-oriented films of a semicrystalline polymer, a process commonly used in many technologies.

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Elastic anisotropy and kink band formation in oriented polymers

Pertsev

Vladimirov

1982

J Mater Sci Lett

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Multiple kinks in lamellar linear polyethylene

Cited by 9 publications

References 14 publications

3D Damage Micromechanisms in Polyamide 6 Ahead of a Severe Notch Studied byIn SituSynchrotron Laminography

3D Damage Micromechanisms in Polyamide 6 Ahead of a Severe Notch Studied byIn SituSynchrotron Laminography

Microbuckling Instability and the Second Yield during the Deformation of Semicrystalline Polyethylene

Elastic anisotropy and kink band formation in oriented polymers

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