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  • 1
    Electronic Resource
    Electronic Resource
    A boundary element simulation of compression mold filling (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 413-420 
    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: This paper presents the development of the boundary element equations for the compression molding process of isothermal Newtonian fluids. It shows the numerical implementation of the boundary element equations and presents a simple method of carrying out the domain integral present in the governing equations. The results and accuracy of a boundary element simulation are discussed, and the numerical results compared to experimental values.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280703
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  • 2
    Electronic Resource
    Electronic Resource
    Stereological measurement and error estimates for three-dimensional fiber orientation (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 240-253 
    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: A method is presented for measuring three-dimensional fiber orientation in fiber-reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation-dependent weighting function that corrects for the bias of an area-based sample. Equations are developed for nonuniform fiber lengths, using both number-average and weight-average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second-rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection-molded sample.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320404
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  • 3
    Electronic Resource
    Electronic Resource
    Mixing for reaction injection molding. I. Impingement mixing of liquids (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 875-886 
    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 performance of confined impinging jet mixers, commonly used in reaction injection molding, was investigated. A theory is presented which assumes that large scale mixing is always adequate, provided the mixer operates in turbulent flow, and argues that the scale of segregation of the final mixture should depend on the size of the smallest eddies of the turbulent motion. The theory predicts that a length scale describing the quality of the mixture will decrease like the nozzle Reynolds number to the -3/4 power. Flow visualization experiments were used to find the point of transition to turbulent mixing flow. This transition occurs at a nozzle Reynolds number of 140 for directly opposed nozzles and at higher Reynolds numbers for nozzles angled downstream. Other geometric factors have little influence on the transition point. Quantitative mixing experiments using model fluids support the theory. Momentum ratio is shown to have no effect on mixing quality.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760201307
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  • 4
    Electronic Resource
    Electronic Resource
    Mixing for reaction injection molding II. Impingement mixing of fiber suspensions (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 887-898 
    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 performance of confined impinging jet mixers on suspensions of milled glass fibers in Newtonian liquids is investigated experimentally. Also studied are the performance of these devices in conjunction with an impingement aftermixer and a rotating mechanical mixing aid. In contrast to the behavior of unfilled liquids, fiber suspensions exhibit significant large-scale mixing defects. Over the range of fiber lengths and loadings tested, large-scale mixing quality is found to be dependent on an effective Reynolds number based on the shear viscosity of the suspension at a strain rate characteristic of the length of fibers. Both mixing aids are shown to provide improved mixing quality and could be useful in situations where length of fibers. Both mixing aids are shown to provide improved mixing Quality. and could be useful in Situations where an impingement mixer alone is not adequate.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760201308
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  • 5
    Electronic Resource
    Electronic Resource
    Electrostatic powder mixingPortions of this paper were presented November 6, 1975 at a symposium sponsored by the MIT-Industry Polymer Processing Program. An abbreviated version of this paper was presented at the 1976 Annual Technical Conference of the Society of Plastics Engineers, Inc. (1976)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 16 (1976), S. 657-663 
    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: A device has been developed which uses electrostatic forces to mix powders. This mixer has no moving parts, and the mixture it produces approaches a perfect mixture whereas mechanical devices can at best produce a random mixture. The device is described, as are experiments which exhibit its operation. Also included are a mathematical model describing the behavior of the device, suggestions for scale-up procedures, and h discussion of some closely related concepts of mixing.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760161002
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  • 6
    Electronic Resource
    Electronic Resource
    Stiffness and thermal expansion predictions for hybrid short fiber composites (1990)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 229-239 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A model is developed to predict thermal expansion coefficients and elastic moduli of multi-component (hybrid) composites. The model includes the influences of fiber aspect ratio; isotropic and anisotropic fiber materials; planar, three-dimensional or arbitrary fiber orientation; hollow and solid spherical reinforcements; and voids. The first step in the procedure is to predict the properties of an aligned-fiber single-reinforcement composite for each reinforcement type. Various micro-mechanics approaches are used, depending on the type of reinforcement. A simplified version of Lee and Westmann's theory is found to work well for hollow spherical reinforcements. Performing an orientation average accounts for the spatial orientation of each reinforcement, then an aggregate averaging procedure combines the single-reinforcement properties to model the hybrid. Predictions of the model compare favorably to experimental elastic and thermal properties of short fiber/hollow sphere composites designed for very high speed integrated circuit (VHSIC) board applications.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750110406
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal dispersion in resin transfer moldingThis paper was presented at the 1994 ASME International Mechanical Engineering Congress and Exposition, Chicago, Illinois, Nov. 6-11, 1994. Copyright 1994, American Society of Mechanical Engineers. It appears in the conference publication: R. B. Dessenberger, and C. L. Tucker III, in Advances in Computer-Aided Engineering (CAE) of Polymer Processing, K. Himasekhar, V. Prasad, T. A. Osswald, and G. Batch, eds., HTD Vol. 283, ASME, New York, p. 21-40 (1994). (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 495-506 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This investigation focuses on the effects of thermal dispersion in resin transfer molding (RTM). A set of volume-average balance equations suitable for modeling mold filling in RTM is described and implemented in a numerical mold filling simulation. The energy equation is based on the assumption of local thermal equilibrium and includes a dispersion term. Thermal dispersion is an enhanced transport of heat due to local fluctuations in the fluid velocity and temperature away from their average values. Nonisothermal mold filling experiments are performed on a center-gated disk mold to investigate and quantify dispersion effects. Good agreement is found between the experimentally measured and numerically predicted temperatures, and a function for the transverse dispersion coefficient in a random glass fiber mat is determined. The results indicate that thermal dispersion is important in RTM processes and must be included in simulations to obtain accurate predictions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750160608
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  • 8
    Electronic Resource
    Electronic Resource
    A numerical simulation of short fiber orientation in compression molding (1990)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 164-173 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A computer simulation has been developed to predict the orientation of fibers in a thin, flat part that is compression molded from sheet molding compound. The simulation combines a finite element/control volume simulation of the mold filling flow, a second order tensor representation of the fiber orientation state and a finite element calculation for the transient orientation problem. Sample results and comparison with experiments are presented. Predictions compare favorably with experiments on SMC (sheet molding compound) plaques and a model suspension of nylon fibers and silicon oil.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750110305
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  • 9
    Electronic Resource
    Electronic Resource
    Fiber orientation in simple injection moldings. Part II: Experimental results (1992)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 13 (1992), S. 332-341 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Experimental measurements of fiber orientation are reported for two parts injection molded from nylon 6/6 reinforced with 43 wt% of glass fibers. The parts are a center-gated disk and a film-gated strip. Orientation is measured from polished cross sections and reported as a function of position, both across the thickness and in the flow direction. Both parts have a layered structure, with outer shell layers of flow-aligned fibers surrounding a central core of either random-in-plane (strip) or transversely aligned fibers (disk). The disk also has surface skins with less alignment. The experiments are compared with predictions of the simulation presented in Part I. The simulation predicts the presence, nature, and location of the layers very well. However, it overpredicts the small out-of-plane fiber orientation and places the core-shell transition too close to the midplane. A comparison with selected experimental results suggests that the major source of error is the closure approximation used by the fiber orientation equation. The simulation is exercised for a variety of cases to show the importance of material and process parameters. A polymer matrix with a small power-law index or a large heat of fusion gives a thicker core and is less likely to have a skin. Injection time is an important parameter, but injection temperature and mold temperature have little effect on fiber orientation.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750130410
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  • 10
    Electronic Resource
    Electronic Resource
    Fiber orientation in simple injection moldings. Part I: Theory and numerical methods (1992)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 13 (1992), S. 317-331 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper sets out the theory and numerical methods used to simulate filling and fiber orientation is simple injection moldings (a film-gated strip and a center-gated disk). Our simulation applies to these simple geometry problems for the flow of a generalized Newtonian fluid where the velocities can be solved independently of fiber orientation. This simplification is valid when the orientation is so flat that the fibers do not contribute to the gapwise shear stresses. A finite difference solution calculates the temperature and velocity fields along the flow direction and through the thickness of the part, and fiber orientation is then integrated numerically along pathlines. Fiber orientation is three-dimensional, using a second-rank tensor representation of the orientation distribution function. The assumptions used to develop the simulation are not valid near the flow front, where the recirculating fountain flow complicates the problem. We present a numerrical scheme that includes the effect of the fountain flow on temperature and fiber orientation near the flow front. The simulation predicts that the orientation will vary through the thickness of the part, causing the molding to appear layered. The outer “skin” layer is predicted only if the effects of the fountain flow and heat transfer are included in the simulation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750130409
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