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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of random glass fiber-reinforced polypropylene for processing (1996)
    Springer
    Journal of polymer research 3 (1996), S. 227-233 
    Details
    ISSN: 1572-8935
    Keywords: Thermoplastic composite ; Needle-punching ; Cycle time ; Processing window ; Solidification rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract DSC thermal analysis and multi-channel recording have been used to investigate the processing conditions for fiber-reinforced thermoplastic composites. The process combined the film stacking and intermingled fiber techniques using needle-punching to improve the fiber-matrix distribution. The preheating temperature and mold temperature for fiber-reinforced polypropylene composites were in the ranges of 180 ≈ 200 °C and 60 ≈ 100 °C, respectively. DSC analysis and X-ray methods showed the presence of an a crystalline form for PP and PP/GF with the cooling rate at 10 °C/min. Increasing the cooling rate to 20 °C/min, they revealed the presence of a mixture of the monoclinic a crystalline form and the hexagonal β crystalline form. A multi channel recorder was used to determine the completion of impregnation on multi-layer glass fiber reinforced polypropylene, which could significantly reduce the manufacturing cycle time. The main steps in the processing cycle on the surface of composite or inside the composite were determined. The concept of a processing window with respect to solidification rate and molding pressure is introduced and briefly discussed. The mechanical properties of fiber-reinforced polypropylene composite inside the processing window were better than those outside the processing window and were comparable to GE AZDEL®.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01493492
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  • 2
    Electronic Resource
    Electronic Resource
    Toughening behavior of elastomer-modified polycarbonates based on the j-integral (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 792-803 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The J-integral method to determine the fracture toughness of tough and ductile polymeric materials previously developed has been applied to the elastomer-modified polycarbonates. This investigation compares three different methods to obtain Jc: the conventional crack growth length, the stress whitening zone, and the newly developed hysteresis method. Jc values obtained from these three comparative methods are fairly close. The hysteresis method has the advantage over the other two methods of obtaining Jc without requiring the measurement of the crack growth length or the stress whitening zone, therefore avoiding the controversy in defining crack blunting. Results also indicate that the effect of elastomer quantity in polycarbonate on Jc is insignificant as long as the crack is in a stable condition. Higher elastomer contents in polycarbonate result in higher dJ/dΔa, dJ/dΔl, and tearing modulus (Tm). This indicates that the elastomer toughening mechanism is due to the increase of the energy required for crack growth extension. The hysteresis loss energy is directly related to the size of the crack tip plastic zone, and the presence of more elastomer indeed increases the crack tip plastic zone, thus making the polycarbonate tougher. Besides, the presence of elastomer tends to increase the crack initiation displacement and shift the failure modes from an unstable fracture. Jc and the criterion for crack initiation based on rate change of hysteresis energy are discussed in detail.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321206
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  • 3
    Electronic Resource
    Electronic Resource
    Fracture toughness of acrylonitrile-butadiene-styrene by J-integral methods (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1433-1439 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J1c values, whereas the ASTM E813-87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J1c obtained from the E813-81 or the hysteresis method.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351803
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  • 4
    Electronic Resource
    Electronic Resource
    Fracture toughness of high-impact polystyrene based on three j-integral methods (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 1867-1880 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three J-integral methods and their modified versions have been used to characterize the fracture toughness of high-impact polystyrene (HIPS) with different thicknesses. The Jc values obtained were highest from the E813-87 method, followed by the E813-81 method, then by the hysteresis method. The hysteresis method based on the steep rising of hysteresis energy under constant displacement-controlled loading in Jc determination has many advantages over the ASTM E813-81 or the E813-87 method. The requirement of crack growth length measurements is no longer necessary and the controversial issue on the crack blunting line can also be avoided. The E813-87 method resulted in significantly higher Jc values for polymers, but the modified version of E813-87, by moving the offset line from the original 0.2 to 0.1 mm, resulted in comparable Jc values. Since crazes as the main failure mechanism for HIPS, well-defined crack blunting does not expect to occur and the Jc obtained by the original E813-81 based on the theoretically predicted blunting line is indeed slightly higher. The modified version of E813-81 by neglecting the blunting line in Jc determination is believed to be more reasonable for HIPS. The nature of polymers will determine whether the crack tip will be blunted, partially blunted, or not blunted. ASTM E813-81 is appropriate for those polymers with a well-defined blunted crack tip (such as elastomer-modified polycarbonate), whereas the modified version of ASTM E813-81 seems better for those polymers with craze as the main failure mechanism (such as HIPS). Experimental results indicated that this hysteresis method is able to inherently adjust the crack blunting effect and therefore can be applied to any type of ductile polymer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070471017
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