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  • 1
    Electronic Resource
    Electronic Resource
    Fracture mechanisms of poly(ethylene terephthalate) and blends with styrene-butadiene-styrene elastomers (1997)
    Springer
    Journal of materials science 32 (1997), S. 4749-4758 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Poly(ethylene terephthalate) (PET) was blended with 5 wt% of an elastomeric block copolymer. The hydrogenated styrene-butadiene-styrene (SEBS) elastomers were functionalized with 0–4.5 wt% maleic anhydride grafted on the midblock. Notched tensile tests in the temperature range −40–55°C differentiated among the blends in terms of their toughness. The least effective elastomer was the unfunctionalized SEBS; all the functionalized SEBS elastomers effectively increased the toughness of PET. Fractographic analysis indicated that PET and the blend with unfunctionalized SEBS fractured through a pre-existing craze. Although adhesion of the unfunctionalized SEBS to the matrix was poor, the elastomer strengthened the craze somewhat, as indicated by an increase in length of the pre-existing craze when final separation occurred. A functionalized SEBS caused the fracture mechanism to change from crazing to ductile yielding. Graft copolymer formed by reaction of PET hydroxyl end groups with the anhydride in situ was thought to act as an emulsifier to decrease particle size and improve adhesion. These factors promoted cavitation, which relieved the triaxiality at the notch root and permitted the matrix to shear yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018678913914
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  • 2
    Electronic Resource
    Electronic Resource
    Cooperative cavitation in rubber-toughened polycarbonate (1995)
    Springer
    Journal of materials science 30 (1995), S. 587-595 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Particle cavitation in the stress-whitened zone ahead of a semicircular notch in polycarbonate blended with a core-shell rubber was characterized by transmission electron microscopy. Cavitation of rubber particles at five locations in the stress-whitened zone was correlated with the local stress and strain history. It was found that cavitation initiated some distance ahead of the notch when a mean stress condition was met. Initially, only a fraction of the particles cavitated and these were randomly distributed. Single cavitated particles grew into cavitated domains by cooperative cavitation of nearby particles until cavitation was arrested when shear yielding of the matrix provided an alternative mechanism for relief of strain energy. Far from the notch, where the stress state approached uniaxial tension, cavitated domains grew into linear arrays of cavitated particles. A mechanism of cooperative crazing in microlayer composites of polycarbonate and styrene/acrylonitrile copolymer was adapted to cooperative cavitation of core-shell rubber particles. It was proposed that cooperative cavitation of nearby particles occurred by impingement of a small plastic zone that formed at the equator of a cavitated particle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356315
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Co-operative microbuckling of two fibres in a model composite (1996)
    Springer
    Journal of materials science 31 (1996), S. 2747-2755 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cooperative fibre microbuckling, a compressive failure mechanism in unidirectional fibre-reinforced composites, was studied in a model system composed of two polyamide fibres in a transparent silicone matrix. The transparent matrix permitted direct observation of fibre microbuckling during compression. In all cases fibres buckled in a sinusoidal pattern with a critical wavelength characteristic of the fibre diameter and the modulus ratio of the fibre and matrix as observed previously with single fibre composites. At smaller separation distances, the two fibres microbuckled co-operatively in the common plane. At larger separation distances, the fibres microbuckled non-co-operatively in different planes. A stress overlap criterion based on the in-plane shear stress is proposed for co-operative fibre microbuckling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687311
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation of fatigue crack propagation in polyethylene pipe specimens of different geometries (1997)
    Springer
    International journal of fracture 84 (1997), S. 159-173 
    Details
    ISSN: 1573-2673
    Keywords: fracture ; fatigue ; polyethylene ; crack propagation ; accelerated failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Correlation in mechanisms and kinetics of step-wise fatigue crack propagation in polyethylene pipe specimens of different geometries is studied experimentally. It is shown that crack propagation in a non-standard specimen cut from a real pipe and conserving the pipe geometry can be effectively simulated using a standard compact tension specimen. Good correlation in both kinetics of step-wise crack propagation and fractography between the specimens is achieved if experimental conditions are chosen to assure equal values of (a) stress intensity factor and (b) stress intensity factor gradient at the initial notch tips. These results extend previous technique of fatigue accelerating slow crack growth used to predict lifetime of polyethylene pipes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007354600584
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  • 5
    Electronic Resource
    Electronic Resource
    Correlation of stepwise fatigue and creep slow crack growth in high density polyethylene (1999)
    Springer
    Journal of materials science 34 (1999), S. 3315-3326 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetics and mechanism of slow crack growth in fatigue and creep of high density polyethylene were studied. The relationship between fatigue and creep was examined by varying the R-ratio (the minimum/maximum loads in the fatigue loading cycle) in the tensile mode such that loading ranged from mainly dynamic (R = 0.1) to static (R = 1.0, creep test). The stepwise crack propagation mechanism characteristic of long-term failures in polyethylene was observed for all loading conditions studied. Fatigue fracture kinetics allowed for extrapolation to the case of creep failure, which suggested that short-term fatigue testing can be used to predict long-term creep fracture properties. The size of the craze damage zone ahead of the arrested crack tip was controlled only by the mean stress, however the lifetime of the zone was determined by both the maximum stress and the mean stress. Crack growth rate was related to the maximum stress and the mean stress by a power law relationship, which described crack growth over the entire range of loading conditions studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004616728535
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Study of polyethylene pipe resins by a fatigue test that simulates crack propagation in a real pipe (1998)
    Springer
    Journal of materials science 33 (1998), S. 3313-3319 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A fatigue test that simulates the step-wise crack propagation found in pipes in the field, and uses a standard compact-tension specimen, was employed to study and rank crack resistance of various pipe resins. The thermal history during compression moulding of the test specimens strongly affected fracture kinetics. It was found that crack-resistant properties of in-service pipe were best reproduced if compression-moulded plaques were fast cooled under load. This procedure was used to prepare specimens from candidate pipe resins for fatigue testing. The resins were compared in terms of discontinuous crack growth kinetics. The ranking based on resistance to fatigue crack propagation correlated with results of a standard PENT creep test. However, fatigue failure times were an order of magnitude less than the standard creep times. After comparing the initiation and failure times of the resins with detailed kinetics of step-wisse crack propagation, a simplified and rapid procedure is proposed which calls for evaluating only the first jump after initiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013229128686
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  • 7
    Electronic Resource
    Electronic Resource
    Polymer microlayer structures with anisotropic conductivity (1999)
    Springer
    Journal of materials science 34 (1999), S. 1461-1470 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Continuous layer-multiplying coextrusion offers a new approach for processing metal-filled polymers into conducting structures. In this process, filled and unfilled polymers are combined into unique structures with many alternating layers of two or more components. The total number of layers can range from tens to thousands. The ability of microlayering to “organize” anisotropic particles was used to obtain metal-filled polypropylene tape with highly anisotropic electrical properties. Orientation of metal flakes by microlayering increased the anisotropy in resistivity by two orders of magnitude over compression molding. Isolation of individual filled layers by alternating filled and unfilled layers resulted in materials with many independent conducting pathways. Filled layers with 10% (v/v) copper flakes or 15% (v/v) nickel flakes were conductive only if the filled layers were thick compared to the thickness of the flake particles. When the thickness of the filled layers approached the particle thickness, the conductive properties were lost. This behavior was understood by comparing the three-dimensional arrangement of flakes in thick conductive layers with the two-dimensional particle layout of thin non-conductive layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004527205239
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  • 8
    Electronic Resource
    Electronic Resource
    Block copolymers as compatibilizers for blends of linear low density polyethylene and polystyrene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 667-683 
    Details
    ISSN: 0887-6266
    Keywords: blend modulus ; compatibilizers ; polyethylene/polystyrene blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Compatibilization of blends of linear low-density polyethylene (LLDPE) and polystyrene (PS) with block copolymers of styrene (S) and butadiene (B) or hydrogenated butadiene (EB) has been studied. The morphology of the LLDPE/PS (50/50) composition typically with 5% copolymer was characterized primarily by scanning electron microscopy (SEM). The SEB and SEBS copolymers were effective in reducing the PS domain size, while the SB and SBS copolymers were less effective. The noncrystalline copolymers lowered the tensile modulus of the blend by as much as 50%. Modulus calculations based on a coreshell model, with the rubbery copolymer coating the PS particle, predicted that 50% of the rubbery SEBS copolymer was located at the interface compared to only 5-15% of the SB and SBS copolymers. The modulus of blends compatibilized with crystalline, nonrubbery SEB and SEBS copolymers approached Hashin's upper modulus bound. An interconnected interface model was proposed in which the blocks selectively penetrated the LLDPE and PS phases to provide good adhesion and improved stress and strain transfer between the phases. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330416
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  • 9
    Electronic Resource
    Electronic Resource
    Stepwise fatigue crack propagation in polyethylene resins of different molecular structure (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2355-2369 
    Details
    ISSN: 0887-6266
    Keywords: fracture ; fatigue ; polyethylene ; molecular weight distribution ; short chain branch content ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Stepwise fatigue crack propagation in a range of polyethylene resins, some of which are candidates for use in pipes for natural gas distribution, was studied. Examination of the effect of molding conditions on fatigue crack propagation in a pipe resin indicated that fast cooling under pressure produced specimens with the same crack resistance as specimens taken from a pipe extruded from this resin. The mechanism of stepwise crack propagation in fatigue was the same as reported previously for creep loading. Observations of the region ahead of the arrested crack revealed a complex damage zone that consisted of a thick membrane at the crack tip followed by a main craze with subsidiary shear crazes that emerged from the crack tip at an angle to the main craze. The effects of molecular parameters, such as molecular weight, comonomer content, and branch distribution, on the kinetics of fatigue crack propagation were examined. Correlation of creep and fatigue crack resistance made it possible to relate fatigue fracture toughness to molecular parameters by invoking concepts of craze fibril stability developed for creep. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2355-2369, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Multicomponent latex IPN materials. I. Morphology control (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2193-2206 
    Details
    ISSN: 0887-624X
    Keywords: multicomponent ; latex ; interpenetrating polymer networks ; IPN ; core/shell ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of novel structured latex particles with interpenetrating polymer network (IPN) cores and glassy SAN shells were developed in an attempt to investigate the feasibility of these polymers as both toughening and damping agents in thermoplastics. The IPN cores were composed of one impact part (polybutadiene based) and one damping part (acrylic based, with Tg around +10°C). The particle morphologies of these polymers were determined by TEM. The glass transitions and mechanical behavior of the polymers were characterized from DMS. The effect of different components on the final core/shell particle morphologies and mechanical properties was studied. The mechanical behavior of core/shell particles with IPN cores was also compared with that of separate core/shell and multilayered core/shell particles. In addition, normal core/shell synthesis (rubbery part first then the glassy part) and inverted core/shell synthesis (glassy part first then the rubbery part) were performed to provide another access for morphology control. It was found that the core/shell latex particles with poly(butyl acrylate) based copolymers are more miscible than poly(ethylhexyl methacrylate)-based copolymers. The high grafting efficiency of poly(butyl acrylate) plays an important role in governing phase miscibility. The latex particles synthesized by the inverted core/shell mode showed higher miscibility than the normal synthesized ones. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2193-2206, 1997
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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