bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of eccentricities on the fracture of off‐axis fiber composites
Authors: Chamis C. C. , Sinclair J. H. 
Published: December 2004

AbstractFinite element analyses were performed to investigate theoretically the effects of in‐plane and out‐of‐plane eccentricities, bending or twisting, and thickness nonuniformity on the axial stress and strain variations across the width of off‐axis specimens. The results are compared with measured data and are also used to assess the effects of these eccentricities on the fracture stress of off‐axis fiber composites. Guidelines for detecting and minimizing the presence of eccentricities are described.
Carbon fiber structure and stability studies
Authors: Gibbs Hugh H. , Wendt Robert C. , Wilson Frank C. 
Published: December 2004

AbstractA study has been made of the thermal‐oxidative stability of several commercially available carbon fibers. Significant differences in the weight loss behavior were observed in air aging studies run on the bare fibers at 600°F (589 K). The stability of high temperature laminates, such as those based on NR‐150 polyimide precursor solutions, was found to be directly affected by the stability of the reinforcing carbon fibers. In studies carried out to determine the reasons for carbon fiber instability, residual sodium sulfate was found to be the principle destabilizing factor. A mechanism whereby the sodium sulfate promotes the oxidation of carbon in the presence of air is proposed.
Young's modulus of uniform density thermoplastic foam
Authors: Progelhof R. C. , Throne J. L. 
Published: December 2004

AbstractA comparison of experimental data for zero strain Young's modulus of uniform density thermoplastic foam for short times has been made with several theoretical and empirical correlations. An analysis of the variance of the data with the predicted values from the many models indicated that the simplistic density squared relationship adequately described the modulus of the foam for basic engineering calculations.
Transverse tensile characteristics of fiber composites with flexible resins: Theory and test results
Authors: Christensen R. M. , Rinde J. A. 
Published: December 2004

AbstractA theoretical and experimental investigation has been conducted of the transverse tensile properties of flexible‐resin/ glass‐fiber composite lamina. The objective is to increase the elongation at failure of a lamina in a state of transverse tension so that when a lamina is used in a laminate configuration, it does not suffer premature failure (e.g., failure at a lower strain level than that for a lamina in fiber direction tension). We show that the mode of failure in the transverse tensile lamina differs greatly from that in the neat resin. The failure mode in the lamina form is found to be brittle fracture. From this, it follows that the controlling neat resin property is the low elongation modulus rather than the elongation at failure. Significant improvements in the transverse tensile strain at failure were obtained for the flexible‐resin/glass‐fiber systems studied.
Compatible glassy polyblends based upon poly(2,6‐dimethyl‐1,4‐phenylene oxide): Tensile modulus studies
Authors: Kleiner Lothar W. , Karasz Frank E. , MacKnight William J. 
Published: December 2004

AbstractThe mechanical behavior of compatible glassy polyblends based upon poly(2.6‐dimethyl‐ 1,4‐phe nylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the tensile modulus of the blend was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory, and lattice fluid theory. The modeling of the properties of mixtures via Simplex lattice design is also presented. Finally, attention is given to the development of compatibility criteria based upon tensile modulus and density measurements.
Studies on poly(vinyl chloride)—copper composites. Part 2: SEM studies of the fracture surfaces
Authors: Bhattacharyya Swapan K. , De Sadhan K. , Basu Sanjay 
Published: December 2004

AbstractScanning electron microscopy (SEM) studies of fracture surfaces of poly(vinyl chloride)—copper composites at various metal loadings and different processing conditions reveal characteristic features. In general, metallic fillers introduce brittleness, while plasticizers increase the ductility of the composites. Results of the fracture studies have been correlated with the properties of the composites reported earlier.
A simple procedure of accounting for physical aging in the prediction of the modulus of glassy plastic materials
Authors: Booij H. C. , Minkhorst J. H. K. 
Published: December 2004

AbstractThe basic relationships are presented for predicting the creep and stress relaxation as a function of physical aging, loading time, and temperature of amorphous polymers processed under such conditions that their thermal treatment amounts to a quench from the melt to the glassy state. A nomogram construction, based on these relations, is proposed and developed for a particular polymer, namely an extrusion type acrylonitrile‐butadiene‐styrene (ABS), RONFALIN EST. The applicability of the procedure is restricted to the isothermal viscoelastic behavior at low stresses and strains of unplasticised amorphous plastic materials quenched from the melt to the glassy state.
Predicting the creep rupture life of polyethylene pipe
Authors: Barton S. J. , Cherry B. W. 
Published: December 2004

AbstractA number of techniques have been developed in the past for the prediction of the dependence of the creep rupture life of polyethylene pipe on applied stress and temperature. It is now proposed that, using a modified form of the activated rate procss equation in which the activation volume varies predictably with temperature, a generalized equation may be derived which describes the “brittle” creep rupture curve over a range of temperatures, and also allows the use of a Larson‐Miller type equation. Since the known “ductile” creep rupture curve at 20°C can be extrapolated from measurements carried out over a short period at room temperature in the laboratory, the intersection point between the extrapolated “ductile” curve and the calculated “brittle” curve can easily be calculated. If the proposed method is applied to creep rupture data obtained from Hoechst AG (GM5010, HDPE pipe) as an example, a transition at about 11 years is predicted.
Time‐temperature cure behavior of epoxy based structural adhesives
Authors: Doyle Michael J. , Lewis Armand F. , Li Hin‐Mo 
Published: December 2004

AbstractTime/temperature cure profile diagrams of a nylon‐epoxy adhesive and a rubber‐modified epoxy based structural adhesive have been established from isothermal‐cure time torsional braid analysis measurements. The characteristic zones of liquid, gel‐rubber and glassy state behavior are noted on the diagrams. With the nylon‐epoxy adhesive, the time/temperature cure profile is ill‐defined since all the TBA data had to be obtained (due to the particular curing agent involved) at isothermal conditions above the glass temperature of the finally cured adhesive. In comparison, the rubber‐modified epoxy system showed distinct zones reflecting the various rheological states traversed during the thermosetting process. The dynamic mechanical. (Rheovibron), morphology, and adhesive joint strength properties are examined as a function of cure cycle.
Dynamic thermomechanical investigation of polymeric systems supported on inert substrates
Authors: Cowie J. M. G. 
Published: December 2004

AbstractThe use of inert supports for the study of mechanically weak polymer systems is becoming more widespread, particularly since Gillham established its acceptability in the torsional braid technique. A description and review of work using glass braid, glass filter mat and cellulose mat supports is presented. This consists of coverage of the dynamic mechanical response of a series of mono and di‐alkyl esters of polyitaconic acid ranging in ester chain length from C1 to C18. The major features, e.g., glass and sub‐glass transitions, are identified and evidence of a double glass transition was found, when the ester chain length exceeds C6. The relaxations of ring systems in the glass phase are also examined. Controversy over the precise value of Tg for amorphous polyethylene has continued for some time and our attempt to resolve the problem has centered on a study of hydrogenated polybutadienes. The data obtained support the proposition that the polyethylene Tg is about 195K and that its γ‐relaxation, suggested by some workers to be the Tg, arises from crankshaft motion involving methylene sequences of 6 to 10 units. Other topics discussed include the damping characteristics of low molecular weight polymers such as poly(dimethylsiloxane), polystyrene, and poly(propylene oxide) with special reference to the existence of Tn transitions.
Influence of molecular weight on crystallization rate of oriented, glassy nylon 6
Authors: Engler Philip , Carr Stephen H. 
Published: December 2004

AbstractDifferential scanning calorimetry and wide angle X‐ray diffractometry were used to investigate the effects of molecular weight and molecular weight distribution on the crystallization kinetics of oriented, glassy nylon 6. The samples had number average molecular weights ranging from 10,000 to 42,000 and polydispersity indices ranging from 2.0 to 3.1. Noncrystalline films were prepared by quenching molten films between plattens chilled with liquid nitrogen. These films were drawn 4X and 5‐1/3X, and the resultant uniaxial orientation was observed to enhance markedly the room temperature crystallization kinetics. Although macroscopic deformation can be assumed to be affine at the molecular level, it is hypothesized that wholechain molecular relaxation occurs at rates inversely proportional to the square of molecular weight, thereby creating a distribution of extension ratios which reflect the actual molecular weight distribution. Thus, the crystallization rate and the degree of crystallinity depend on the fraction of high molecular weight molecules present in the sample. Given two samples with the same molecular weight, the one with the broader distribution crystallizes more rapidly. Similarly, samples having the larger molecular weight crystallize to a greater extent when two samples have the same molecular weight distribution.
Influence of molecular weight on the creep behavior of undiluted polyisobutylenes
Authors: La Mantia F. P. , Acierno D. 
Published: December 2004

AbstractThe elongational behavior in constant force experiments has been considered for three samples of commercial polyisobutylene. The results compare favorably with the predictions of two existing non‐linear theories as long as the samples deform homogeneously. Some qualitative observations have been made with reference to the “failure point”, i.e., the point where a non‐homogeneous deformation begins.
Effect of bonding temperature on the joint strength of polyolefln/butyl rubber and polyolefin/ethylene‐vinylacetate copolymer
Authors: Sung Nak‐Ho 
Published: December 2004

AbstractThe effect of bonding temperature on the peel strength of adhesive joints, polyolefin/butyl rubber and polyolefin/ethylene‐vinylacetate copolymer, has been investigated. The peel strength, measured at room temperature, undergoes a sharp transition from its low values to higher values as the bonding temperature is changed from below to above, the melting point of the substrate. This increase in peel strength is accompanied by changes in failure mode from the apparent interfacial failure to cohesive failure through the adhesives. Investigation of the interface using Fourier Transform Infrared Internal Reflection spectroscopy and interference microscopy indicates that the sharp increase in the peel strength at the melting temperature of substrate is associated with the presence of an interdiffused layer at the interface.
Viscosities and normal stress coefficients of high impact polystyrene‐mineral oil mixtures
Authors: Kruse R. L. , Southern J. H. 
Published: December 2004

AbstractMeasured melt viscosities and primary normal stress coefficients are presented for a well‐characterized, rubbermodified polystyrene as a function of shear rate and mineral oil diluent concentration. The logarithmic blending relationship accurately predicts the observed data. Melt relaxation times and shear compliance data are also calculated. The compliance numbers are consistent with molecular models based on a simple dumbbell (appropriately modified for rubber and mineral oil addition).
Chemiluminescence of incompatible polymer mixtures
Authors: Naito K. , Kwei T. K. 
Published: December 2004

AbstractChemiluminescence of an incompatible mixture of polystyrene and cis‐1, 4‐polybutadiene was studied. The luminescence characteristics of the component polymers are preserved in the incompatible blend and the intensity for the blend can be represented as the surface‐area‐average of the individual intensities.
A simplified method for analyzing mold filling dynamics. Part II: Extensions and comparisons with experiment
Authors: Stevenson James F. , Chuck Winston 
Published: December 2004

AbstractA dimensional analysis based on four parameters has been developed previously to predict injection pressure; clamp force, and bulk temperature for the injection molding of amorphous materials in center‐gated disk‐shaped cavities. In this paper geometric and semicrystalline‐materials approximations are introduced and tested for extending the previous analysis to include multigated thin cavities and semicrystalline materials. The combination of these approximations and the previous analysis, known hereafter as the Radial Flow Method (RFM), greatly simplifies the analysis of mold filling. The geometric approximation, which is based on a simple model for the axial stress distribution in the cavity, is shown to give reasonable predictions when compared with experimental data and a numerical two‐directional flow simulation for the filling of an off‐center‐gated rectangular cavity with acrylonitrilebutadiene‐styrene copolymer (ABS). The semicrystallinematerials approximation, in which heat capacity and viscosity changes during crystallization are neglected, is shown to give good agreement with experimental data for the filling of a center‐gated disk‐shaped cavity with polypropylene. As an illustration, the Radial Flow Method is used to analyze the molding of a large, thin‐wall automobile interior trim panel. The inlet melt temperature, mold‐wall temperature, part thickness, injection rate, viscosity and gate locations are varied in a series of calculations to determine the relative effectiveness of these variables in lowering the injection pressure and Clamp force. The results obtained with the Radial Flow Method are in good agreement with those obtained by a finiteelement simulation of two‐directional flow.
Effects of dispersion on flow and mechanical properties of polymer blends
Authors: Kapuscinski M. , Schreiber H. P. 
Published: December 2004

AbstractBlends of linear polyethylene and ethylene‐propylenediene elastomer, representing the entire composition range, were prepared under various conditions of shear intensity. It was found that both viscoelastic flow parameters and mechanical properties at large deformation respond strongly to variations in shear history of material preparation. Mechanical degradation of the polymers not being detected, it is postulated that property variations are due to morphological effects related to domain sizes of the two components and to the ease of molecular diffusion across domain boundaries. Thus, mechanical properties develop over finite times of mixing, consistent with the attainment of steady states in domain sizes. Maximum sensitivity of mechanical properties to mixing variables is found for 50/50 blends of the polymers, which have maximum interdomain contact areas. It appears feasible to develop desired balances of flow and mechanical properties in such polyblends through the close control of component dispersion processes.
Chemorheology of crosslinked epoxy resins subjected to large strains
Authors: Buchman A. , Katz D. 
Published: December 2004

AbstractThe previously reported work on chemorheological changes occurring in two epoxy resins when aged under large strains at temperatures above their Tg was extended. Ageing times up to 100 h were applied and the phenomenon of orientation occurring in these samples was investigated, mainly by measurements of their birefringence index. It was found that the orientation of the air‐aged samples, when studied at room temperature, depended on the ageing conditions (strain, temperature, time) and was not uniform throughout the bulk of the samples, being higher in two narrow external layers and lower in the core layer. After reheating oriented samples in air without strains for different lengths of time at temperatures above Tg, disappearance of the orientation in the external layers was observed. This is probably due to oxidation and degradation occurring in the network and scission of part of the network links, mainly those strained due to orientation. The decrease of orientation, especially in the inner layers of the polymer samples, was much slower when the reheating of the oriented‐ and unstrained samples took place in an inert atmosphere, this showing again the great influence of oxygen when it participates in ageing and heating processes of epoxy resins.
Rheo‐optical studies on the deformation mechanism of semicrystalline polymers. VIII. Dynamic x‐ray diffraction of a high‐density polyethylene film having row‐structure of C‐axis orientation
Authors: Suehiro Shoji , Yamada Takeshi , Kyu Thein , Fujita Ken‐Ichi , Hashimoto Takeji , Kawai Hiromichi 
Published: December 2004

AbstractDynamic x‐ray diffraction is employed to scrutinize the structural origin of the α mechanical dispersion of a highdensity polyethylene having preferentially oriented rownucleated cylindritic texture around the machine direction (MD). Results indicate that the α1 dispersion is associated with two kinds of orientation processes of crystallites: (1) the orientation process involving the rotation of crystallites around the crystal b‐axis (lamellar axis) dominates in the MD specimen; (2) the other process accompanying the rotation of crystallites or lamellar segments around their crystal a‐axis dominates in the TD (transverse direction) specimen. The complex apparent crystal lattice compliances show no frequency dependence in the real component and no appreciable value in the imaginary component, indicating that the α1 process is definitely associated with the intercrystalline process, but not relavent to the intracrystal process. However, at elevated temperatures, the complex lattice compliances exhibit a remarkable frequency dependence, suggesting that the α2 dispersion concomitant to intracrystalline nature takes place in this time scale. The α2 dispersion was found to be more pronounced upon stretching along the lamellar axis (TD) than normal to it (MD).
The effect of moisture on the mechanical behavior of a nylon‐epoxy adhesive
Authors: Agarwal Pawan K. 
Published: December 2004

AbstractThe mechanical properties of a commercial nylon‐epoxy resin have been studied using a sensitive creep apparatus which employs a frictionless levitation magnetic bearing. Isothermal creep measurements over a temperature range of 30‐170°C and covering a time scale of five decades were made on the wet and dry state of the material. Following the usual time‐temperature reduction scheme, master curves for each state were constructed from the experimental data. The effect of moisture was found to be more than that of a simple plasticizer. The steepness of the reduced curves in the transition region was determined and the distribution function of retardation times of the two states of the sample were calculated. The problem of predicting the physical state of the bulk adhesive at higher temperatures was found to be complicated, possibly due to the presence of nylon crystallites.
The role of inter‐ and intra‐links in the transformation of folded chain lamellae into microfibrils
Authors: Tarin P. M. , Thomas E. L. 
Published: December 2004

AbstractIn this study we investigate the effect of crystallization rate on the extensibility (draw ratio) of spherulitic polyethylene film uniaxially deformed at room temperature. Draw ratios for deformed films increased with increasing crystallization temperature. Transmission electron microscopy of the microfibrillar structures revealed and interconnected network of fibrils. The degree of connectivity between microfibrils was found to decrease with increasing‐crystallization temperature. A model of the deformation process is developed in which inter‐ and intra‐link (extended chain fibers formed during crystallization) distribute the applied stress, initiate the micronecking process and influence the amount of chain unfolding during drawing.
A dielectric study of the crystal and amorphous fractions in oriented polyethylenes
Authors: Boyd Richard H. , Yemni Tarik 
Published: December 2004

AbstractPolyethylenes have relaxation processes separately assignable to the crystal and amorphous components. The possibility thus presents itself for studying the interaction between the two phases by investigating the anisotropy of the separate relaxation processes induced by overall orientation of the material. Such a study was carried out here by the dielectric method on samples rendered dielectrically active by the introduction of a few carbonyl groups by oxidation. In addition to the usual advantage of ease of frequency variation, the dielectric method in this case has a very great advantage in interpretation resulting from the similarity of dielectric constants of the two phases. In specimens oriented by solid‐state extrusion, it was found that the crystalline relaxation process (α) develops the expected anisotropy resulting from dipoles normal to C‐axis alignment in the extrusion direction. In branched polyethylene (BPE) no accompanying anisotropy of the amorphous β and γ processes was observed. Since the extrusion was carried out well above the glass temperature of the amorphous component, this indicates that constraints from the crystal phase are not sufficient to prevent dissipation of amorphous orientation by segmental motion. However in linear polyethylene (LPE) (where there is no well‐developed β process) some anisotropy of the γ process was observed. It is proposed that a higher degree of constraint of the amorphous component by the crystals in LPE results in suppression of the glass‐rubber (β) relaxation and permits amorphous orientation to accompany crystal orientation.
Some relationships between injection molding conditions and the characteristics of vitrified molded parts
Authors: White James L. , Dietz Wolfgang 
Published: December 2004

AbstractThe various mold filling phenomena influencing the characteristics of fabricated parts are surveyed. The phenomena leading to jetting in injection mold filling are considered. These are associated with the magnitude of swell by the melt as it exits the gate into the mold. Special attention is given to the influence of non‐isothermal runner flow. A theory of extrudate swell of polymer melts with temperature profiles is developed using Tanner's unconstrained recovery theory. In the. absence of jetting, mold filling by a simple advancing front takes place. The hydrodynamics of the advancing front and the stress fields in the flowing melt are determined. Analysis and modeling are presented based on the use of hydrodynamic lubrication theory involving a solid layer along the mold wall and a hot isothermal melt core. This theory is compared with experimental measurements of pressure losses in mold filling. The development of birefringence in injection molding processes is analyzed. Birefringence distributions are due to frozen‐in flow birefringence. A new experimental study is presented and its results compared with theoretical predictions. The problem of thermal stresses in injection molded parts is considered.