ISSN:0730-6679    

DOI:10.1002/adv.1988.060080301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA numerical simulation of multilayer coextrusion flows has been undertaken for polymer melts used in producing multilayered plastic sheets. Viscosity data and other material properties are used for typical melts and adhesives applied in coextrusion. Industrial designs have been employed for feedblock geometry and multimanifold vane flat dies. The analysis is based on the lubrication approximation theory (LAT), which treats the flow locally as fully developed. A Newton‐Raphson iterative scheme is employed to solve the equations for a pressure‐driven flow ofNnumber of layers (N⩽ 11). For a given total flow rate and flow rate ratios (or correspondingly total sheet thickness and individual layer thicknesses), the solution provides the interface locations and individual pressure drops that each extruder has to supply. The shear stresses at the channel walls are checked as a criterion for proper design. The die design or melt combinations are altered to produce smooth shear stresses with no humps or discontinuities at the points of confluence. A Adiabatic temperature rises are also computed based on the pressure drops in the system. Such an analysis provides a quick qualitative as well as quantitative insight into the proper design and melt combinations for multilayer sheet coextr

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractIn compression molding of composite parts, it is important to minimize the temperature variation in the part during processing for consistent quality. A mold heating analysis and optimization scheme has been developed that allows computation of temperature variation on the mold/part surface, and optimizes the location and power of heaters. The heat transfer coefficients for a given mold can also be theoretically calculated. The validation of the analysis was carried out by two sets of experiments: the first one measured the heat loss from the mold under different boundary conditions, and the second one the temperature variation on mold/part boundary for theoretically determined power histories for a specified temperature history. The experimental data compared well with theory and provide a satisfactory validation of the analysis. The present work provides a useful tool to a design engineer and allows the mold heating system design on a scientific basis, thus eliminating the trial and error approach.

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe friction and wear behavior of silicone‐impregnated fiber‐reinforced thermoplastics has been investigated as a function of normal load in air, water, and oil lubricants using a two‐body abrasion tester. The measured tribological data have been phenomenologically explained by a wear/friction equation derived from the concepts of crack propagation and wear failure

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe behavior of silicone rubber materials subjected to uniaxial stress fields cannot be predicted by classical mechanical theory which is based on linear stress–strain relationships. Nor do theories based on “ideal elastomer” concepts work well when extensions exceed 30%. For these reasons, there are few design specifications related to the use of silicone rubber sealants for structural applications. This paper presents a theoretical approach used to predict the behavior of silicone rubber under uniaxial stress fields. The model is based on the concept of the classical Maxwell treatment of viscoelasticity and stress relaxation behavior. However, the Hookean spring component of the Maxwell element is replaced with an ideal elastomer component. With this substitution, the new model permits the crosslink density of the silicone elastomer to be estimated from test data and allows a stress level to be predicted as a complex function of extension, crosslink density, absolute temperature, and relaxation time. Simple uniaxial tensile tests were performed on two commercial silicone rubber sealants. Their experimental behavior was compared to the predicted performance based on the new viscoelastic model. Agreement was found to be quite good. It is hoped that the model, therefore, will help in the basic understanding of structural sealant behavior and perhaps lead to better design specifications for structural gl

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA method of determining fiber orientation in composites using wide angle X‐ray diffraction (WAXD) is described. This approach is based upon examining the alignment of the highly oriented crystalline fibers. X‐ray studies were carried out using Kevlar [poly(p‐phenylene terephthalamide) (PPTA)] fibers suspended at a 0.31 volume fraction loading in a polycarbonate matrix. A pole figure device was used to determine the orientation distribution and average orientation factor of the PPTA crystallographic chain axes relative to reference axes located in the test specimen. We prepared ideally oriented uniaxial and bioaxial composites as reference specimens using a compression molding machine. The fiber orientations in capillary extrudates, slit die extrudates, cold rolled sheets, and injection‐molded specimens were examined by WAXD. The capillary extrudates showed uniaxial orientation but the slit die extrudates and cold rolled sheets exhibited biaxial orientation. Injection‐molded specimens contained complex states of fiber or

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY