ISSN:0032-3888    

DOI:10.1002/pen.760080202

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractTwo independent methods for predicting the deformation of free openings of arbitrary shape in a viscoelastic plate are illustrated.The first method is experimental and is based on the interference of two systems of lines representing the initial and final positions of the material. To demonstrate the moire method, the creep compliance function for polymethylmethacrylate is determined as preliminary information. This function is used as input data in the ensuing theoretical analysis to insure realistic viscoelastic behavior.The second method involves techniques to approximate viscoelastic displacements from known elasticity solutions and known material properties.The methods are applied to two examples: (1) The square hole—to determine the motion of an opening of complicated shape; and (2) an ellipse loaded at 45°—to indicate qualitative agreement with an existing prediction of the motion of cracks in a viscous p

ISSN:0032-3888    

DOI:10.1002/pen.760080203

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe stress‐strain characteristic of polymeric binders and solid propellants are dependent on the crosslink density, molecular weight between crosslinks, molecular weight distribution in the binder formulation, volume fraction of filler, and the interaction between the binder and filler particles. This investigation is directed toward elucidation of solid propellant microscopic response and failure mechanisms through characterization of the constitutive effects of crosslink density, molecular weight distribution and curing agent ratio in the binder formulation, and filler fraction. This was accomplished on the ERLA/PBAA propellant system through investigation of three binder formulations with the same curing agent ratio but different crosslink densities; five binder formulations with different curing agent ratios; and four formulations with up to 69.9% by volume of filler.Uniaxial stress‐strain characteristics were determined on each formulation at displacement rates of 0.2 to 20.0 in/min at isothermal test conditions ranging from 75 to −90°F. The failure characteristics of a viscoelastic material represent a curve in the three‐dimensional space of stress, strain, and time. The ultimate property data on each formulation are presented as projections of this failure curve on the stress‐strain, stress‐time, and strain‐time planes, respectively. Relationships are developed for the dependence of the stress‐time, strain‐time, and stress‐strain failure envelopes on the volume fraction of bound rubber, crosslink density, molecular weight distribution and curing agent ration in the binder component, and the volum

ISSN:0032-3888    

DOI:10.1002/pen.760080204

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe paper discusses the deformational behaviour of thermoplastics, particularly in relation to their utilization through rational engineering design procedures. It describes the comprehensive systems of data that are replacing the old single datum quantities published hitherto and comments briefly on the corrdination of materials testing through the activities of B.S.I. Committee PLC/36.

ISSN:0032-3888    

DOI:10.1002/pen.760080205

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe elasticity of polymer melts is of major concern in the processing of plastics. It is usually reflected by dimensional changes. Since the swelling of polymer extrudates depends on the capillary dimensions and the volumetric flow rate, the blow‐up must be examined over a range of conditions. Of course, the swelling is also dependent on polymer structure. Consequently, variations in materials and operating conditions necessiate changes in tooling. This paper describes the swelling behavior of several different polymer types and illustrates that viscosity measurements can not be used to predict elasticit

ISSN:0032-3888    

DOI:10.1002/pen.760080206

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractA simple, versatile biconical rehemoter has been developed. This device provides shear creep and creep recovery data for polymer melts over a temperature range of 200–500°F. and a range of applied shear stresses from 2 × 103to 9 × 105dynes/cm2.Extensive reheological data have been obtained for two samples each of polyisobutylene and high‐density polyethylene. These illustrate the value of the device in obtaining data useful for predicting and understanding the processing properties of polymer

ISSN:0032-3888    

DOI:10.1002/pen.760080207

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractAn experimental investigation of the dynamic mechanical response of molten polymers was performed using the Maxwell Orthogonal Reheometer. One purpose of the study was to evaluate the effect of molecular weight distribution on the temperature dependence of viscoelastic properties. Data were obtained over a range of temperatures for both monodisperse and polydisperse materials which indicate that viscoelasticity is highly temperature dependent only for monodisperse polymers. On a molecular basis the reduction in temperature sensitivity for polydisperse materials logically can be attributed to the influence of the low molecular weight species present in a distribution on the relaxation spectrum. Since the relaxation spectrum largely determines all viscoelastic functions, the observations made from th dynamic data shown in this paper can be generalized to all viscoelastic experiments.

ISSN:0032-3888    

DOI:10.1002/pen.760080208

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractThe fracture toughness of a variety of sharply notched tension, bending and rotating disc specimens of PMMA is examined using linear fracture mechanics. It is observed that rapid fracture with a brittle glassy appearance usually follows a period of slow crack growth, denoted by fan shaped markings of local ductility, though still brittle overall. In this near brittle regime the fracture toughness is sensitive to strain rate so that high values of effective surface energy are easily induced by rapid testing or notch bluntness. At impact rates the toughness increases again. For design purposes, in the absence of environmental effects, the onset of slow cracking and rapid (glassy) fracture, can be associated with fracture toughness K1cof about 800 Ibf/in3/2(90 kg/cm3/2) and 1600 Ibf/in3/2(180 kg/cm3/2) respectively. Detailed studies have not been made on other materials but a guide to the levels of notch toughness and notch brittle temperatures are given for several plastics.

ISSN:0032-3888    

DOI:10.1002/pen.760080209

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractAn idealized polymer model is used to examine the magnitude of the catastrophic tensile breaking energy and stress in terms of primary and secondary bonding forces. Computed strengths for primary and secondary bonding are respectively 8000 and 500 times larger than observed values of a common thermoplastic. From other considerations, the glass transition temperature for both elastomeric and thermoplastic polymers is found to show a linear dependence on the cohesive energy per unit length of polymer chain.In special polymer model, the influence of polymer chains on unidirectional elongation is shown to be a function of chain size. Elongation data reported on a series of modified polycarbonates exhibit a correlation with chain size as described by the model. Published data on the polycarbonate series are used to evaluate the correlation between observed deformation breaking energies and cohesive energies calculated from glass transition temperatures.

ISSN:0032-3888    

DOI:10.1002/pen.760080210

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY

摘要:

AbstractTime‐temperature equivalence was used to predict the long term engineering behavior of highly crystalline ethylene‐butene copolymers. The long term behavior (greater than 1000 hrs.) was accurately predicted from tests of short duration (30 hrs.). This time‐temperature principle was applied to stress‐relaxation and creep at stresses, strains and temperatures normally encountered in engineering practices. It was also used to solve a design problem involving the creep deformation of metal plastic laminates. Long term tests were performed to confirm the predicted results. This technique was not applicable to rubber modified polystyrene because of an unexpected transition

ISSN:0032-3888    

DOI:10.1002/pen.760080211

出版商:Society of Plastics Engineers, Inc.    

年代:1968

数据来源: WILEY