Recent advances in slow crack growth modeling of polyethylene materials

Almomani, Abdulla; Mourad, Abdel‐Hamid I.; Deveci, Süleyman; Wee, Jung-Wook; Choi, Byoung-Ho

doi:10.1016/j.matdes.2023.111720

Cited by 22 publications

(4 citation statements)

References 419 publications

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“…This behavior has already been observed in the literature for HDPE filaments and standard specimens in virgin and chemically aged conditions from engineering stress-strain curves [8,[23][24][25][26][27][28]. Comparing behaviors of outer and inner layers (Figs.…”

Section: (D) Asupporting

confidence: 70%

Filament manufacturing via external grooving of an HDPE pipe wall: RSM optimization and mechanical tests validation

Mammeri,

Bouacha,

Chaoui

et al. 2024

Res. Eng. Struct. Mat.

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In order to explore the possibilities of manufacturing and testing specimens from extruded HDPE pipes to retrace material inherent properties, continuous filaments are circumferentially machined by grooving. The proposed protocol imposes to keep to a strict minimum damage effects since semi-crystalline polyethylene is sensitive to deformation and heat. A Taguchi plan is adopted with inputs (cutting speed; feed rate; depth of cut). The modeled performance characteristics are roughness criteria (Rt; Ra) and temperature (T°). Using ANOVA and response surface methodology, the optimized values are 137.0 m/min, 0.4 mm/rev and 4.0 mm respectively for Vc, f and ap. At the highest desirability, the values of Rt (1.100 μm), Ra (0.223 μm) and T (36.44 °C) are satisfactory compared to turning data. Tensile tests on specimens from outer, middle and inner pipe show that (σ–ε) curves are reproducible with a pronounced drawing zone, especially for the inner pipe layers. Practically, the elasticity modulus is increased by 43% from outer to inner layers while the utmost difference in the elastic limit is ~ 5%. Concerning failure strain, the increase is 47% meaning that the material shows a great predisposition to ductility. This behavior is related to the higher crystallinity in internal pipe layers.

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Section: (D) Asupporting

confidence: 70%

Filament manufacturing via external grooving of an HDPE pipe wall: RSM optimization and mechanical tests validation

Mammeri,

Bouacha,

Chaoui

et al. 2024

Res. Eng. Struct. Mat.

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“…The cavitation should also promote easier fragmentation of surrounding crystals, rapidly changing the local stress state. [ 122,168,186,187 ] A decrease in the degree of crystallinity and crystal size at low strain and the subsequent increase to a plateau at high strain was observed in Figures 20 and 21, respectively. It suggests fragmentation of the crystal blocks occurs (Figures 22b,c), which is followed by the reorientation of fragments and the reorganization of the unfolded chains and disentangled chains in the amorphous region into crystal blocks (Figure 22e).…”

Section: The Evolution Of Microstructure and Characterization Of A Si...mentioning

confidence: 90%

Evolution of the Deformation‐ and Flow‐Induced Crystallization and Characterization of the Microstructure of a Single Spherulite, Lamella, and Chain of Isotactic Polypropylene

Sharaf,

Kloczkowski

2023

Macro Chemistry & Physics

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Isotactic polypropylene (iPP) is a frequently used polymer in industrial processing and scientific research, used as a model material. This review highlights some current and forefront issues in polymer science and engineering. This review alludes to classical deformation schemes to interpret the complicated deformation in isotactic polypropylene as a semicrystalline polymer. Also, due to the complex hierarchical structures of crystallized polymers, we are concerned mainly with the progress on the multi‐scale and multi‐stage microstructural evolution covering each deformation stage from the initiation of plasticity until failure, particularly in terms of crystalline morphology changes. Specifically, the characterization of the microstructure evolution of a single spherulite, lamella, and chain of isotactic polypropylene will be emphasized and mentioned. Here, we are most interested in the results obtained from stretching (strain‐induced) orientation and crystallization studies accompanied by the in situ scattering and spectroscopy techniques offering a detection window from nano to micrometer scale, which should be able to reflect the microstructural changes at different length scales of interest.During polymer processing, the melts are frequently subjected to shear or/and elongation flow fields, producing flow‐induced molecular chain orientation in the melt. The oriented molecular chains crystallize differently than those encountered under quiescent conditions. Thus, orientation‐induced crystallization has long been an object of intense interest. A vast body of research was reported about the effects of preorientation on the crystallization of various polymers. Among them, iPP is most frequently studied since its diversified structure and morphology are very sensitive to changes in processing conditions and molecular parameters.This article is protected by copyright. All rights reserved

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“…Since slow crack growth (SCG) and environmental stress cracking (ESC) as damage mechanisms must be considered the major causes of failure in application of polyolefins, 1,2 their detailed understanding is relevant for the development of resilient polyolefin materials. SCG and the related ESC, which can be regarded as slow crack growth accelerated by contact with certain liquid media, especially affect high‐density polyethylene (HDPE).…”

Section: Introductionmentioning

confidence: 99%

Relation of craze to crack length during slow crack growth phenomena in high‐density polyethylene

Schilling,

Niebergall,

Marschall

et al. 2024

Polymer Engineering & Sci

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The craze‐crack mechanism occurring in high‐density polyethylene (HDPE) causing slow crack growth and environmental stress cracking is investigated in detail with respect to the relation of crack length and the related craze zone. This is essential for the understanding of the resulting features of the formed fracture surface and their interpretation in the context of the transition from crack propagation to ductile shear deformation. It turns out that an already formed craze zone does not inevitably result in formation of a propagating crack, but could also undergo ductile failure. For the examination, the full notch creep test (FNCT) was employed with a subsequent advanced fracture surface analysis that was performed using various imaging techniques: light microscopy, laser scanning microscopy, scanning electron microscopy, and X‐ray micro computed tomography scan. FNCT specimens were progressively damaged for increasing durations under standard test conditions applying Arkopal, the standard surfactant solution, and biodiesel as test media were used to analyze the stepwise growth of cracks and crazes. From considerations based on well‐established fracture mechanics approaches, a theoretical correlation between the length of the actual crack and the length of the preceding craze zone was established that could be evidenced and affirmed by FNCT fracture surface analysis. Moreover, the yield strength of a HDPE material exposed to a certain medium as detected by a classic tensile test was found to be the crucial value of true stress to induce the transition from crack propagation due to the craze‐crack mechanism to shear deformation during FNCT measurements.Highlights Progress of crack formation in high‐density polyethylene is analyzed by different imaging techniques Determined growth rates depend on distinction between craze zone and crack The ratio of the present crack to the anteceding craze zone is validated theoretically The transition from crack propagation to ductile shear deformation is identified An already formed craze zone may still fail by ductile mechanisms

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Recent advances in slow crack growth modeling of polyethylene materials

Cited by 22 publications

References 419 publications

Filament manufacturing via external grooving of an HDPE pipe wall: RSM optimization and mechanical tests validation

Filament manufacturing via external grooving of an HDPE pipe wall: RSM optimization and mechanical tests validation

Evolution of the Deformation‐ and Flow‐Induced Crystallization and Characterization of the Microstructure of a Single Spherulite, Lamella, and Chain of Isotactic Polypropylene

Relation of craze to crack length during slow crack growth phenomena in high‐density polyethylene

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