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  • 1
    Digitale Medien
    Digitale Medien
    A study of the fatigue behavior of fiber reinforced nylons (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 242-251 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A phenomenological model combining a Weibull distribution function with a kinetic equation for flaw growth has been used to describe the static tensile strengths and fatigue lives of short graphite-fiber reinforced nylon 66 materials. A simple Weibull function of the form \documentclass{article}\pagestyle{empty}\begin{document}$ P\left( {\sigma _b } \right) = \exp - \left( {{{\sigma _b } \mathord{\left/ {\vphantom {{\sigma _b } {\hat \sigma }}} \right. \kern-\nulldelimiterspace} {\hat \sigma }}} \right)^{9.5} $\end{document} described the distribution of static strengths. The scale factor \documentclass{article}\pagestyle{empty}\begin{document}$ {\hat \sigma } $\end{document} varies with the annealing treatment and, in general, is a function of environmental variables. The cumulative distribution of breaking times in fatigue can be characterized by a translated three parameter Weibull function \documentclass{article}\pagestyle{empty}\begin{document}$ P\left( {t_B } \right) = \exp - \left\{ {\left. {\left( {\frac{{\sigma _{\max } }}{{\hat \sigma }}} \right)^{16} + \frac{{t_B }}{{\hat t}}} \right\}} \right.^{0.59} . $\end{document} The average time to break (which is related to the time scale factor \documentclass{article}\pagestyle{empty}\begin{document}$ {\hat t} $\end{document}), appears to be a function of the flaw growth rate. The distribution equation has been found to predict the number of half cycle failures and is thus a valid model for the proof testing of large populations. An electrical resistivity method was developed to measure flaw growth rates in prenotched cantilever beams. Experimental data fit the following equation: ln (Δa/Δn) = -88.88 + (12.46 ± 5.68) ln (Keff)max. The correlation coefficient was 0.81. From curve fitting of fatigue data it appeared that flaw growth rate varied with the ninth power of flaw length (Δa/Δn) = Ma9. The direct measure of flaw growth rate using electrical resistance gave Δa/Δn = Ma6.23±2.84 with 90 percent confidence. The two measurements overlap within the 90 percent confidence bands, but predictions of fatigue life using the flaw propagation data were not good. Scanning electron microscope studies showed that specimens with a short fatigue life have glassy, fibrillated fracture surfaces while specimens with a long fatigue life exhibit a high degree of ductility in portions of the fracture surface. These differences are traced to differences in the size and shape of flaws.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760150403
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  • 2
    Digitale Medien
    Digitale Medien
    The fatigue behavior of graphite fiber reinforced nylon (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 634-642 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The fatigue lives of graphite fiber reinforced nylon composites were related uniquely to the tensile strengths of the materials. The distributions of tensile strength and fatigue life were measured and correlated with either two- or three-parameter Weibull functions. For a specific population, there existed a unique relationship between the two cumulative distributions. Thus, if the effect of an environmental variable on the distribution of strength is measured, the effect on the fatigue life can be estimated. It was also found that the mechanism of fatigue failure was influenced by the technique of fabrication. Compression molded materials failed through an isothermal, brittle mode of fracture, while injection molded materials failed in a ductile, thermal mode.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760180806
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  • 3
    Digitale Medien
    Digitale Medien
    Fatigue crack propagation in, graphite fiber reinforced nylon 66 (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 512-518 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The rate of fatigue crack propagation in graphite fiber reinforced nylon 66 was measured. A model of the form å = β [Kmax1-γ ΔKγ]r was used to correlate the rate of crack propagation å with the maximum stress intensity Kmax and the amplitude of the stress intensity ΔK experienced by the notched specimen during the fatigue test. The quantities β, γ and r were constant at fixed temperature and frequency of the test. It was also found that there exists both an upper and a lower threshold of stress intensity for the slow ropagation of damage during fatigue. The mechanism of crack propagation in the short graphite fiber reinforced nylon was found to be similar to the growth and fracture of crazes in thermoplastics. The propagation of damage at the crack tip is controlled by matrix deformation, cavitation, fiber breakage and fiber pullout. Damage can propagate in the absence of crack growth until a critical point is reached at which time the material fractures catastrophically.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760190709
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  • 4
    Digitale Medien
    Digitale Medien
    Crosslinked oligoethylene glycols: Correlation between their structure and some rheological properties (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 801-811 
    Details
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Six oligoethylene glycols were crosslinked with triphenylmethane triisocyanate, and polymers with systematically changing network chain lengths were obtained and investigated. The 10-sec. torsion moduli versus temperature, glass transition temperatures, and cohesive energy densities of the polymers were determined and studied. The 10-sec. torsion modulus versus temperature plots show that all six polymers have a glassy transition and rubbery region of rheological behavior. The front factor calculated from the equation for the torsion modulus in the rubbery region when measured values of the modulus were used was compared with the front factor computed from equations that take into consideration molecular structures of the rubbery networks. With the exception of the case of crosslinked diethylene glycol the agreement in all the other cases between the values obtained for the front factor in both ways was good. In the investigated range of temperatures the polymers have below the glass transition temperature another transition point. The solubility parameters of the polymers, calculated from swelling experiments, were with the exception of the first member in the series almost identical.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1968.160060501
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  • 5
    Digitale Medien
    Digitale Medien
    Craze relaxation: A rapid and simple method for glass transition temperature determination in amorphous polymers (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 2049-2050 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1971.070150821
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  • 6
    Digitale Medien
    Digitale Medien
    Blends of poly(ethylene terephthalate) and a polyarylate before and after transesterification (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1629-1638 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Blends of poly(ethylene terephthalate) (PET) and a copolyester of bisphenol A-terephthaloylisophthaloyl (PAr) (2:1:1) have been studied both before and after transesterification. The physical blends exhibit phase separation in their amorphous states: a pure PET phase and a mixed PAr-rich phase. In spite of this phase separation, PET crystallinity in blends, normalized to PET fraction, surprisingly goes through a maximum at 25% PAr content. The transesterfied copolymers are noncrystallizable and exhibit a single Tg between those of starting polymers, PET and PAr.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1984.070290517
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  • 7
    Digitale Medien
    Digitale Medien
    Blends of poly(butylene terephthalate) and a polyarylate before and after transesterification (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 367-378 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Blends of poly(butylene terephthalate) (PBT) and a copolyester of bisphenol-A with 50% terephthalate-50% isophthalate (PAr), before and after transesterification, have been studied by thermal and dynamic mechanical tests to determine crystallinity and phase behavior. Blends without transesterification, as prepared by solution precipitation, show a single Tg, indicating amorphous miscibility of PBT and PAr. A melting-point depression for PBT crystals is not observed; this means that PBT crystallizes excluding PAr and the entropy of melting is small. The highest fractional crystallinity for PBT is obtained at 20-35% of PAr. Transesterified blends were obtained by holding the physical blends at 250°C for up to 16 h. The transesterified systems show higher Tg's than the corresponding physical blends and also show a marked melting-point depression and lesser PBT crystallinity at the corresponding increased PAr content.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1983.180210304
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