bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of treatment on the surface composition and energy of carbon fibers
Authors: Wu G. M. , Schultz J. M. , Hodge D. J. , Cogswell F. N. 
Published: December 2004

AbstractThe surface composition and energy of carbon fiber has been carefully analyzed and quantified. Untreated, AU, surface‐treated, AS, and heat‐treated AHT fibers were all studied. AS fiber was surface‐treated by an electrolytic oxidation process. AHT fiber was heat‐treated at elevated high temperatures under vacuum. X‐ray photoelectron spectroscopy (XPS or ESCA) was used to investigate the surface elemental concentration of carbon fibers. The corresponding surface free energies of these fibers were calculated from the contact angles measured by a dynamic contact angle analyzer. Results showed a strong correlation between the surface treatment and heat‐treatment history and the surface chemistry of carbon fibers. After oxidation treatment, the surface free energy was increased by adding functional group elements (oxygen and nitrogen). However, these added elements could be removed by high temperature treatment under vacuum. The diffusion of O, N, and Na was discussed. The correlation between oxygen and nitrogen concentration and carbon fiber surface free energy has been plotted. These fibers would be used to quantify the relationship between carbon fiber surface free energy and the interfacial shear strength of the fiber‐polymer interface.
Dynamic mechanical analysis of epoxy composites plasticized by water: Artifact and reality
Authors: Chateauminois A. , Chabert B. , Soulier J. P. , Vincent L. 
Published: December 2004

AbstractThe plasticization of a glass/epoxy unidirectional composite by water has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). The analysis of the thermomechanical spectra of the water aged material revealed the apperance of a splitting of the tan δ peak associated with the α transition. This splitting was found to be dependent on the experimental conditions, i.e., the temperature scan rate, the straining frequency, and the initial water content on the composite. A thermogravimetric analysis (T.G.A) of the wet specimens has shown that this effect could be attributed to an enhanced drying of the specimens above the glass transition, during the DMTA temperature scan. A differential plasticization of the epoxy network at the aging temperature can therefore not be invoked from the appearance of a splitting of the DMTA spectra. In conditions where the sample drying was minimized, plasticization effects on the thermomechanical properties of the composite were found to be temperature independent and reversible after re‐drying of the aged material. Owing to the filling of hygrothermally induced cracks with water, the composite sensitivity to plasticization can be underestimated significantly at elevated aging temperature.
The adhesion of elastomer‐coated glass fibers to an epoxy matrix. Part I: The effect of the surface treatments on the tensile strength of the glass fibers
Authors: Ahlstrom C. , Gerard J. F. 
Published: December 2004

AbstractE‐glass fibers were subjected to various surface treatments to study the interfacial adhesion with an epoxy matrix by means of the fragmentation test. The glass fibers considered were both untreated and treated with γ‐aminopropyltriethoxysilane (γ‐APS). In addition, glass fibers were coated with a thin layer of a crosslinkable elastomer including (or not) a silane coupling agent. To evaluate the effect of the coating process, the glass fibers were also passed through the pure solvent (washed fibers). The tensile strength of glass fibers at short length (near the critical length, lc, for the fragmentation test) cannot be measured directly, thus, extrapolation techniques were used. The Weibull statistics technique was applied and accurately described the tensile strength data of the tensile strength at various fiber gauge lengths for the different surface treatments. Nevertheless, the Weibull parameter, m, changes with the gauge length, and therefore, the extrapolation value at lc depends on the method. The tensile strength of the silane‐treated glass fibers is higher than for the untreated fibers, in agreement with reported data. This effect could be attributed to the protection against water provided by the silane sizing. The coating process does not induce any damage of the glass fibers since the washed fibers display mechanical properties close to those obtained for the untreated fibers. An additional effect is observed for the elastomer‐coated fibers which present the highest tensile strength. This effect could be attributed to an improved protection and/or elimination of the weakest filaments in the glass strand during the treatment.
Polyamide 6—long glass fiber injection moldings
Authors: Bijsterbosch H. , Gaymans R. J. 
Published: December 2004

AbstractThe injection molding ability of long glass fiber reinforced polyamide pellets was studied. The injection moldable materials were produced by a melt impregnation process of continuous fiber rovings. The rovings were chopped to pellets of 9 mm length. Chopped pellets with a variation in the degree of impregnation and fiber concentration were studied. The injection molded samples were analyzed for fiber concentration, fiber length, and fiber orientation. Dumbbell‐shaped tensile bars were made to evaluate the mechanical properties. The fibers in the tensile bars had a high orientation in the flow direction and minor fiber concentration gradients were observed. The fiber lengths decreased with fiber concentration from 1.6 mm for a 2 vol% to 0.6 mm for a 25 vol% system. The tensile and impact properties increased considerably with fiber concentration. A low degree of impregnation in the pellets of the fibers resulted in somewhat lower tensile and impact properties.
Effects of fiber mat architecture on void formation and removal in liquid composite molding
Authors: Patel N. , Lee L. James 
Published: December 2004

AbstractLiquid composite molding (LCM) processes such as resin transfer molding and structural reaction injection molding are considered to be high potential processes for the mass production of composite parts. The resin injection step in LCM consists of two simultaneous flows: bulk mold filling and tow wetting. This complexity often results in the entrapment of air in the composite part, which is known to result in degradation of part performance, In this work, systematic investigation of the resin flow behavior through various types of glass fiber reinforcements is carried out by flow visualization. The objective is to relate the fiber mat architecture to the micro scale flow pattern and void formation, movement, and removal. An optical image analysis and processing technique is developed to help quantify void formation. Void formation is related to liquid properties and fiber‐liquid contact angle. Although the focus of the study is LCM, the results can be directly applied to other composite manufacturing processes that involve advancement of resin in a dry fiber reinforcement.
Polymer applications in three dimensional linear fracture mechanics analysis
Authors: Smith F. W. 
Published: December 2004

AbstractA discussion is given of three types of experimental techniques which make use of polymers for the verification of theoretical solutions to three‐dimensional linear fracture mechanics problems. The three techniques discussed are designated as the fatigue method, the photoelastic stress‐freezing method and the static fracture method. These techniques employ poly(methyl methacrylate) sheets which are cut into appropriate fracture mechanics specimen geometries or castable epoxies which may be cast into flat plates or other appropriate shapes for investigation. The suitability of these materials for linear fracture mechanics testing is discussed and the quality of results obtained is described.
Rapid crack propagation and arrest in polymers
Authors: Kobayashi A. S. , Mall S. 
Published: December 2004

AbstractPublished results on dynamic fracture toughness vs crack velocity relations of polyester resin (Homalite‐100), epoxy resin Araldite‐B, modified epoxy resins and polycarbonate are reviewed. Commonality between the seemingly diversified experimental results as well as the existences of minimum dynamic fracture toughness,KIm, and crack arrest stress intensity factor,KIa, as inherent material properties are discussed.
Calculation of molecular parameters for stepwise polyfunctional polymerization
Authors: Miller Douglas R. , Valles Enrique M. , Macosko Christopher W. 
Published: December 2004

AbstractOur recursive method is extended to calculate several new parameters for stepwise polyfunctional polymerization. In the pregel region we calculate weight average molecular weight, Mw, for polydisperse reactants and effective average functionality, fe, of a reacting mixture. These quantities are useful for systems employing reactive oligomers. We also calculate weight average number of branches per molecule, Bw, and the weight average of a longest chain. These should be useful for viscosity relations. In the postgel region we give relations for the extent of reaction in the soluble fraction. This result can be used to calculate sol properties directly from existing pregel relations. We also calculate the weight fraction of pendant chains on the gel, wp, and the average molecular weight of the elastically effective network chains, Mc,w.
Moisture effects upon the dimensional stability of an S‐glass/epoxy composite
Authors: McCormick Fred C. 
Published: December 2004

AbstractAn experimental investigation is described of the effects of moisture and a polar solvent upon the changes in the axial dimensions of composite tubes fabricated with S‐glass and an epoxy resin. Test parameters included different axial stress levels, sorption variations, and changes in the short‐beam shear strength with moisture variations. Several wetting and drying cycles were used to establish the reproducibility and reversible characteristics of the observed dimensional changes. Test results are compared and discussed with findings reported by other investigators.
High modulus through lamellar structures nucleated by flow induced fibrous substrates
Authors: Odell J. A. , Grubb D. T. , Keller A. 
Published: December 2004

AbstractExtremely high modulus (up to 1011Nm−2) strands of poly ethylene have been prepared by the controlled crystallization of lamellar overgrowths onto a small quantity of preformed flow‐induced microfibrils. The requirements for achieving a high modulus from a lamellar system are considered, and indicate that high chain extensions may not be needed. The lamellae satisfying these requirements possess a unique taper, the outer edges having a fold length of less than 40Å. This raises new issues relating to crystallization in confined spaces, and space filling by lamellae in bulk samples in general.
Fatigue crack propagation in, graphite fiber reinforced nylon 66
Authors: Dibenedetto A. T. , Salee Gideon 
Published: December 2004

AbstractThe rate of fatigue crack propagation in graphite fiber reinforced nylon 66 was measured. A model of the form å = β [Kmax1‐γΔKγ]rwas used to correlate the rate of crack propagation å with the maximum stress intensityKmaxand the amplitude of the stress intensity ΔKexperienced by the notched specimen during the fatigue test. The quantities β, γ andrwere constant at fixed temperature and frequency of the test. It was also found that there exists both an upper and a lower threshold of stress intensity for the slow ropagation of damage during fatigue. The mechanism of crack propagation in the short graphite fiber reinforced nylon was found to be similar to the growth and fracture of crazes in thermoplastics. The propagation of damage at the crack tip is controlled by matrix deformation, cavitation, fiber breakage and fiber pullout. Damage can propagate in the absence of crack growth until a critical point is reached at which time the material fractures catastrophically.
Sorption and transport in glassy polymers–a review
Authors: Frisch H. L. 
Published: December 2004

AbstractAfter defining Fickian diffusion in rubbery polymers an overview of transport behavior in polymers is presented. Diffusion and sorption below the glass transition are discussed, followed by a review and classification of the various theoretical models which have been proposed to account for these phenomena. A short list of recommendations for future work is included.
Microhardness of extruded high density polyethylene fibers
Authors: Baltá‐Calleja F. J. , Mead William T. , Porter Roger S. 
Published: December 2004

AbstractHigh‐density polyethylene of high tensile modulus has been produced by solid state extrusion using an Instron capillary rheometer. Microhardness measurements on these ultraoriented fibers have been made to assess their perfection from values of the tensile elastic modulus and shear strength. The microhardness tests were measured using a Vickers square diamond. The microhardness increased with the common temperature for crystallization and extrusion, likely due to improvement in the lateral packing of microfibrils. The variation of microhardness with draw ratio is also illustrated.
Melt elasticity of low density polyethylene
Authors: Nguyen My N. , Maxwell Bryce 
Published: December 2004

AbstractThe stress vs strain and strain recovery characteristics of a series of low density polyethylenes of various molecular size and molecular size distributions have been studied in the melt state. The results show that the high molecular size portion of the molecular size distribution dominates the stress vs strain behavior. The high molecular size component causes a large increase in the stress overshoot and steady state stress. The high molecular size component also has a strong influence on the magnitude of recoverable strain, The strain recovery characteristics are dependent on the amount of strain applied. For large strains (above the yield point) the strain recovers slowly to a large extent (Type I). For applied strains below the yield point the strain recovery is rapid and finished in a short period of time (Type II).
Oxygen plasma removal of thin polymer films
Authors: Taylor G. N. , Wolf T. M. 
Published: December 2004

AbstractRelative rates of polymer removal in an oxygen plasma have been measured for 40 polymer samples. The rates of removal are correlated, with structural factors which enhance or retard removal. Strong backbone bonds, aromatic and polar functional groups, and metallic atoms decrease the removal rates. Weak bonds not attached to the‐ polymer backbone have little affect while weak bonds attached directly to the chain or in the chain greatly accelerate removal. Chlorine present in the polymer catalyzes removal. This can be mimicked by mixtures of CF4, and O2 for which much enhanced removal rates are observed.
Model reference optimal steady‐state adaptive computer control of plastics extrusion processes
Authors: Hassan G. A. , Parnaby J. 
Published: December 2004

AbstractThe first true hierarchical automatic optimal control scheme for plastics extrusion has operated satisfactorily in the laboratory. The process operator is only required to specify desired output rate and die inlet melt temperature set‐points. The control variable set‐points are continually set by computer in line with an optimal policy pre‐programmed from off‐line solutions using models for extruder and die behavior. Feedback and feedforward control strategies are used to hold the melt temperature and pressure at die inlet within close tolerances using control actions calculated via process models and applied by a hierarchical cascade controller. The methodology is described by reference to a specific 40 mm diameter screw extruder fitted with a variable geometry annular blow molding die head, processing specific polymers. However, the control procedures are completely general and can be applied to any extruder‐die combination.
Monohole flow test with high‐frequency preheating for evaluating flowability of thermosetting compounds
Authors: Tonogai Saburo , Seto Shoji 
Published: December 2004

AbstractThe flow behavior of molding compounds such as phenolics, melamines, and ureas was examined by a monohole flow test in which the compounds were high frequency‐preheated up to the test temperature just prior to being put into the monohole mold. The effect of temperature, pressure, and water content on the flowability has been clarified as follows: (1) The relation between log flow rate and reciprocal absolute temperature consists of two straight lines with different slopes, showing dual activation energies for flow above and below an inflection point. The phenomenon suggests the existence of a phase transition in a resin flow. (2) The inflection point shifts to the lower temperature side with an increase of pressure and water content. (3) The influence of water content on the flowability varies largely according to compatibility between resins and water. (4) The temperature dependence of flow rate in a urea compound decreases during storage due to the advancement of condensation.
Heat transfer in polymer composites containing thermally active fillers: Mathematical modeling
Authors: Joshi Shriram , Astarita Gianni 
Published: December 2004

AbstractThe heat transfer data recently presented by Migliaresi, et al. are used as the basis for developing two models of the coupled heat transfer‐phase transition phenomena in polymeric composites containing thermally active fillers. Both models represent an extension to heat transfer of ideas which have originated in the analysis of mass transfer phenomena in polymeric materials. The second model is able to correlate all the available data within 0.5°C.
Characterization of the interlaminar shear fatigue properties of SMC R‐50
Authors: Wilson Dale W. , Byron Pipes R. 
Published: December 2004

AbstractThe interlaminar shear fatigue behavior of the sheet molding compound SMC‐R50 has been studied. A thick‐laminate, short beam shear test was employed to characterize S‐N behavior for the material at 21 and 90°C. The shear modulus (Gxy) was determined at 21 and 90°C and the effect of fatigue on modulus at both test temperatures is discussed. Scanning electron microscope (SEM) and optical photomicrographs of pristine and post test specimens were studied to assess the relationship between material microstructure and the observed fatigue results for strength and modulus. The experimental evidence suggests that the fatigue life for this material is determined by a single flaw growth mechanism, rather than a global “wear out” process.
Polymer/concrete composites—A review
Authors: Kirlikovali Ergun 
Published: December 2004

AbstractThe development of polymer/concrete composites is directed at both improved and new construction materials by combining the ancient technology of hydraulic‐cement‐concrete with the modern technology of polymers. The need for such materials has always existed since the traditional construction material portland‐cement‐concrete (PCC) suffers the drawbacks 4 little or no resistance to chemical attack; rapid deterioration under freeze/thaw conditions due to cyclic temperature changes; low tensile, shear and bond strengths; and inherent micro‐structural menaces (voids, shrinkage‐cracks, capillaries) which, individually or in combination with each other, shorten the service life of the structures.
Glass transition temperature (Tg) determination of partially cured thermosetting systems
Authors: Lee C. Y‐C. , Goldfarb I. J. 
Published: December 2004

AbstractPrevious experiments have shown that Tg of a partially cured thermosetting system can be measured with conventional thermal scan methods only if no appreciable additional cure occurred during the scan. For high temperature performance systems, the partially cured Tg is often at a temperature where kinetics rate is very rapid, causing either an observation of a more advanced cured Tg, or only the completely cured system's Tg [Tg (∞)]. Two methods to interpolate the Tg information in spite of additional cure are presented and illustrated with an epoxy resin as a testing material. The Isocure State Curve method is demonstrated with a two‐step curing experiment with the Torsion Impregnated Cloth Analysis (TICA) technique, which is a forced torsion measurement on the Rheometrics mechanical spectrometer, with the resin impregnated on a glass cloth specimen. The calibration method is demonstrated by the post cure experiments of TICA, using the time to loss modulus maximum, and the softening parameter R as the calibration parameters.
Properties of polyether‐polyurethane zwitterionomers
Authors: Hwang Kirk K. S. , Yang Chang‐Zheng , Cooper Stuart L. 
Published: December 2004

AbstractPolyether polyurethanes based on 4,4′‐diphenylmethane diisocyanate (MDI), N‐methyl diethanolamine (MDEA), and polytetraniethylene oxide (PTMO) were synthesized with varying levels of hard segment content. The tertiary amine of MDEA was sulfonated with γ‐propane sultone thereby converting the polyether polyurethane to a polymeric zwitterion. The effect of the chemical composition and the degree of ammonium sulfonation on the extent of phase segregation, and physical properties were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis and tensile testing. It was found that the MDEA chain extender inhibits microphase separation of the polymer in the solid state. As the degree of ammonium sulfonation increases in the zwitterionomers, an improvement of phase separation and domain structure was observed. In addition the tensile properties change dramatically with increasing sulfonate content going from properties characteristic of soft, weak gum rubbers to those of hard, strong thermoplastic elastomers.
The transesterification of bisphenol‐a polycarbonate (PC) and polybutylene terephthalate (PBTP): A new route to block copolycondensates
Authors: Devaux J. , Godard P. , Mercier J. P. 
Published: December 2004

AbstractIn this work, the exchange reaction taking place in molten blends of bisphenol‐A polycarbonate and polybutylene terephthalate was studied. A direct transesterification mechanism catalyzed by titanium residues, present in commercial PBTP, was deduced. The transesterification reaction can be ‐stopped at various levels by additives capable of complexing the titanium catalyst.This work enhances the possibility of a new approach in macromolecular engineering by directly combining polycondensates in a processing machine such as an extruder.
Some rheological aspects of fracture in thermoforming
Authors: Tsai James T. 
Published: December 2004

AbstractThis paper focuses on several aspects of drawability, including the interactions between material parameters, operating temperatures, and frictional properties of the material. The deep draw process for a molten plastic sheet can be described by a simplified model using the characteristics of the normal stress as a lumped parameter. A rapid evaluation of the draw ratio and mold closing speed can be obtained by systematically drawing a series of three draw ratios. The fracture mode should then be examined to determine the appropriateness of molding temperatures. Therefore the maximum attainable draw ratio can be calculated from the elongational viscosity data. To support the analysis, data is provided on the formation of a cup with polystyrene sheets and using Maxwell extensional model as an example.