摘要:

AbstractA recently proposed method for predicting the strains resulting from the application of uniaxial cyclic stresses is developed for application to polymer systems. Experimental results obtained from rectangular cyclic loading tests on prismatic beams and circular plates are compared with theoretical predictions using two sources of basic data, (a) uniaxial isochronous and creep data and (b) deformation data resulting from constant load creep tests conducted on the components. It is concluded that the method would require considerably less computation, to obtain satisfactory accuracy, than the alternative integral superposition methods even for rectangular cyclic loading and would prove much more tractable when applied to other forms of cyclic loading.

ISSN:0032-3888    

DOI:10.1002/pen.760140802

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical model for melting in reciprocating screw injection molding machines is proposed. The model permits the calculation of the solid bed profile as a function of time during the injection cycle. It consists of a dynamic extrusion melting model for the rotation period, a transient heat conduction model with a phase transition for the screw rest period, and a proposed model for the drifting of the beginning of melting during the injection cycle.

ISSN:0032-3888    

DOI:10.1002/pen.760140803

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractBased on the assumption of a constant critical shear strain, an expression for the critical stress at the onset of entrance fracture as a function of polymer concentration has been developed. Experimental results with 10‐25 percent narrow distribution, high molecular weight polystyrene‐benzene solutions show the critical stress to be much lower than that for the polymer melt and in agreement with predicted values. This result is all the more impressive when the contrast in flow behavior at the capillary entrance for melts and solutions is observed. Instead of the rotating toroidal vortices surrounding a 90‐deg material entrance cone observed with polystyrene melt, cine movies of the solution flow birefringence patterns in the capillary entrance region reveal only a stagnant zone surrounding a narrow cone less than 20 deg. At fracture, the cone axis moves in a rotary path circulating about the capillary axis without undergoing the flow discontinuities typical of melt beh

ISSN:0032-3888    

DOI:10.1002/pen.760140804

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractAspects of the present status of structure‐property correlations for linear polycarboranesiloxanes which contain rigid carborane cages and flexible siloxane in‐chain linkages are discussed. Low temperature secondary transitions, glass transitions, crystallization and melting transitions, and high temperature chemical transformations in inert and air atmospheres are emphasized. The linear polymers serve as the basis for new high‐temperature elast

ISSN:0032-3888    

DOI:10.1002/pen.760140805

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe rheology of a high molecular weight polyisobutylene “Vistanex” L‐80 is measured at 20°C under constant stress creep loading in simple shear and simple elongation and compared with published data for biaxial extension. These data can be reduced to a single curve by the application of simple geometric parameters and instability during extensional flows may be interpreted on the basis of the Considère construction. The results are further extended by dynamic measurements to estimate the viscoelastic response of this material over a time scale of nine orders of magnitude. The rheological response shows an approximately linear relationship with stress up to elongation strains of 1.0, and, because of this, the results do not illuminate the present controversy over the selection of different equations of state to represent non‐linear polymer melt flow. However, this body of data, which the authors believe to be the most comprehensive presently available in terms of strain level and deformation geometry, does demonstrate that a viscoelastic polymer can respond to different deformation geometries in a simp

ISSN:0032-3888    

DOI:10.1002/pen.760140806

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractCreep tests at constant values of tensile stress, temperature, and relative humidity for two thermoplastics were conducted for approximately 132,000 hr. The strains, ϵ, for the first 2000 hr of time,t, were described by an equation of the form ϵ = ϵo+ ϵ+tnwhere all other symbols are constants. This equation was found to predict the creep of poly(vinyl chloride) for approximately 132,000 hr with reasonable accuracy. The predicted strains for polyethylene (density 0.924) were somewhat low. Strains during unloading and reloading after 90,000 hr of creep were predicted reasonably well by the Boltzmann superposition princi

ISSN:0032-3888    

DOI:10.1002/pen.760140807

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical analysis using finite element methods has been applied to oriented short‐fiber composites and spherical particle composites in order to predict the influence of a finite layer at the interface on mechanical properties. In this study the interfacial layer has been modeled by assuming that a layer surrounds the interface and that this layer has a modulus of elasticity different than both the fiber and the matrix. The stress distribution near the interface has been determined as a function of the elastic constants of the interface layer and the interface layer volume fraction. This analysis has also been performed for two volume fractions of fibers and two fiber length to diameter ratios. From this stress distribution, the composite modulus and toughness have been determined as a function of interface modulus. It is theoretically shown that the toughness, measured by amount of strain energy absorbed, can be maximized by controlling the interface modulus. Furthermore, recent experimental results appear to verify the theor

ISSN:0032-3888    

DOI:10.1002/pen.760140808

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe generation of pressure in the feed section of an extruder is analyzed. It is concluded that body forces must be considered since they provide the necessary conditions for pressure initiation. Solutions are given which take into account gravity forces in both vertical and horizontal screws together with centrifugal force. Some numerical results are also given which illustrate the practical importance of these effects.

ISSN:0032-3888    

DOI:10.1002/pen.760140809

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760140801

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY