bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the potential for release of conductive fibers from advanced composites by means of thermogravimetric analysis and scanning electron microscopy
Authors: Wentworth Stanley E. , King Abram O. , Shuford Richard J. 
Published: May 2005

AbstractRecently, there has been concern over the effects of accidentally released conductive carbon and graphite fibers on unprotected electrical circuits. Because of their thermal stability, such fibers could be released by the involvement of a resin matrix composite in a fire. A simple method based on thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) has been developed which permits the assessment of release potential from such composites. Dynamic TGA is used to determine temperatures at which significant events such as onset of resin matrix decomposition occur. Isothermal TGA permits a determination of the time required to produce releasable fibers at a given temperature. SEM examination of residues from TGA experiments serves to characterize their physical state which, in turn, permits a more precise assessment of release potential. This method has been used to examine a large number of materials composed of several different fibers in a variety of thermoset and thermoplastic matrices. It is concluded that release potential varies inversely with resin thermal‐oxidative stability and directly with fiber stability. The matching of matrix resin char and fiber stabilities is especially effective in suppressing fiber release.
Properties and structure of polymer concrete composite material with divinyl benzene as a crosslinking agent
Authors: Zeldin A. N. , Kukacka L. E. , Fontana J. , Carciello N. 
Published: May 2005

AbstractA study has been performed to determine the effect of the use of divinyl benzene(DVB) as a crosslinking agent in polymeric binders consisting of mixtures of styrene, acrylonitrile, and acrylamide, on the thermal stability and structure of polymer concretes(PC), containing sand and cement as an aggregate. The results indicate that the inclusion of DVB results in improvements in the thermal and mechanical stability. The improvements are attributed to three‐dimensional cross‐linking of the polymer due to the inclusion of DVB. The influence of the sand‐cement ratio on the structure of PC samples at 240°C are also discussed.
Mechanical properties of polypropylene reinforced with short graphite fibers
Authors: Weiss R. A. 
Published: May 2005

AbstractThe Mechanical properties of injection molded and compression molded graphite fiber‐reinforced polypropylenes are discussed. In general, the tensile properties of polypropylene are significantly improved by reinforcement with graphite fibers and to a greater extent than achieved by glass fiber reinforcement. The failure mechanism of these materials involved a combination of matrix fracture and debonding of the fiber‐polymer interface. The use temperature of these materials is shown to increase with increasing fiber content and the notch sensitivity is reduced.
Viscoelastic behavior of galss‐reinforced epoxy resin
Authors: Nicolais L. , Guerra G. , Migliaresi C. , Nicodemo L. , Di Benedetto A. T. 
Published: May 2005

AbstractThe viscoelastic behavior of epoxy composites containing various percentage of glass microspheres and random short glass fibers was investigated over a wide range of temperatures. The effect of the second phase is to increase the relaxation moduli of the system and to shift the time dependency to higher times. All the data were shifted to a single master curve at a reference temperature by using independent shift factors that were a function of either temperature or filler content.
The rheology and mold flow of polyester sheet molding compound
Authors: Lee L. J. , Marker L. F. , Griffith R. M. 
Published: May 2005

AbstractFlow properties of sheet molding compounds (SMC) were measured by several rhemeters. Shear viscosities of SMC paste can be fitted by the Carreau viscosity equation and reduced to a single master curve by plotting the reduced shear viscosity (η/η0) against reduced shear rate (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} η0/T). The deformation fo glass filled compounds under extensional forces. When the shear forced was applied, the compound defomed like a deck of cards being slid. It behaved essentially like a laminate of many layers. On the other hand, SMC compounds elongated much less before sample failure occurred under the extensional flow. The extensional viscosity was much higher than the shear viscosity. This phenomenon was explained by a solid composite theory and theories developed from local shear flows between adjacent fibers. The flow of SMC compounds during molding showed that the surface layers flowed further than the inner layers when the mold surfaces were hot. This casued inner plies to show through at the surface and resulting in some wavy glass orientation. This phenomenon was explained equalitatively by a heat penetration model.
Fatigue failure mechanisms in polymer composites
Authors: Dao K. C. 
Published: May 2005

AbstractAxial fatigue of two, commercial, talc‐filled polypropylenes was studied. A significant result of our investigation was the identification and characterization of the failure mechanisms and the effects of frequency and hysteretic heating. Frequency was found to be important to the fatigue response of the polymers. At low frequency, fatigue failure appeared to be a process of crack initiation and growth with very little dissipative heating. At high frequency, the fatigue process was dominated by dissipative heating resulting in significant creep and modulus loss, and failure was much accelerated and due mainly to material softening and melting. Correlation of temperature rise with on‐line energy loss in selected experiments enabled us to extract information from the fatigue process. The results provided some quantitative understanding of the different fatigue failure mechanisms at low and high frequencies.
Behavior of discontinuous fiber composites: Fiber orientation
Authors: Byron Pipes R. , McCullough Roy L. , Taggart David G. 
Published: May 2005

AbstractThe behavior of polymeric materials reinforced by discontinuous. Descriptors for the planar and axial orientation distributions are discussed. Predictions of micromechanical models and experimental data are presented to illustrate the influence of orientation state upon elastic constants, thermal coefficients of expansion and tensile strength. Results are presented for the notched strength and compressive creep behavior of the glass/phenolic composite of two orientation states. Finally, the implications of these results upon the design of elements molded of discontinuous fiber composites are discussed.
Extension of the hole‐drilling method to birefringent composites
Authors: Prabhakaran R. 
Published: May 2005

AbstractA complete stress analysis and reliable failure criteria are essential for important structural applications of composites in order to fully utilize their unique properties. The inhomogeneity, anisotropy and inelasticity of many composites make the use of experimental methods indispensable. Among the experimental techniques, transmission photoelasticity has been extended to birefringent composites in recent years. The extension is not straight‐forward, in view of the complex nature of the photoelastic response of such model materials. This paper very briefly reviews the important developments in the subject and then describes the theoretical basis for a new method of determining the individual values of principal stresses in composite models. The mehod consists in drilling very small holes at points where the state of stress has to be determined. Experiments are then described which verify the theoretical predictions. The limitations of the method are pointed out and it is concluded that valuable information concerning the state of stress in a composite model can be obtained through the suggested method.
Monitoring cure of autoclave‐molded parts by dielectric analysis
Authors: Chottiner J. , Sanjana Z. N. , Kodani M. R. , Lengel K. W. , Rosenblatt G. B. 
Published: May 2005

AbstractA study was undertaken to determine the feasibility of using dielectric analysis as a means of monitoring and controlling cure of large closures during autoclave molding. In dielectric analysis, the dissipation factor (DF) and capacitance (C) of the sample are continuously monitored as a function of time, temperature, and frequency. Dissipation factor profiles were established for the suppliers' recommended cure cycle and for modified cure cycles, Good reproducibility was obtained in dissipation factor profiles on subsequent scaling up to production size (7 ft · 20 ft) autoclaves. Good correlation was also observed during production runs of fullscale closures. The effects of cure variables on the dissipation factor profiles and on the mechanical properties of the prepared laminates were analyzed for extent of correlation. Results of this study show: (1) dielectric analysis can be used to monitor autoclave cure of composites, and (2) within limits, process control may be feasible.
The diffusion of liquids into resins and composites
Authors: Marshall J. M. , Marshall G. P. , Pinzelli R. F. 
Published: May 2005

AbstractExisting methods of assessing the resistance of a polymer to environmental attack are of only limited use. A new technique, which utilizes radiolabelled diffusants, has been developed to study the diffusion of liquids into thick sections of polymer‐and glass‐fiber‐reinforced laminates. This technique allows the construction of concentration profiles of the liquid in the polymer at any time, and diffusion coefficients can be calculated from short‐term data. The application of this method of measurement has given a clear picture of the way in which water diffuses into vinyl ester resins and their glass‐reinforced laminates. The effects of stress and damage on this diffusion pattern have been quantified. It has been found that the presence of stress enhances the diffusion, and that the diffusion coefficient is further increased by the presence of a stress concentration. No evidence has been found, however, to suggest that the liquid “wicks” along the fibers when stress concentrations are absent.
Bulk modulus and thermal expansivity of melt polymer composites: Statistical versus macro‐mechanics
Authors: Simha Robert , Jain R. K. , Jain S. C. 
Published: May 2005

AbstractPhysical properties of composites as a function of filler content have been described in the past through models requiring the solution of macroscopic equations of motion for an elastic continuum or, on a more empirical level, by the assumption of various compositional averaging schemes. We discuss a model drawn from our molecular mixture theory. This allows us to avoid the formal problems attending concentrated suspensions and introduces molecular filler‐medium interaction parameters. Comparisons with experimental material and empirical equations involving bulk modulus and thermal expansivity will be given. The theory opens the possibility of determining interfacial strengths from appropriate mechanical and thermal measurements and of predicting one set from another set of data.
Processing and flammability parameters of bismaleimide and some other thermally stable resin matrices for composites
Authors: Kourtides Demetrius A. 
Published: May 2005

AbstractThe effect of processing variables on the flammability and mechanical properties of state‐of‐the‐art and advanced resin matrices for graphite composites were studied. Resin matrices which were evaluated included state‐of‐the‐art epoxy, phenolic‐novolac, phenolic‐Xylok, two types of bismaleimides, benzyl, polyethersulfone, and polyphenylsulfone. Comparable flammability and thermochemical data on graphite‐reinforced laminates prepared with these resin matrices are presented, and the relationship of some of these properties to the anaerobic char yield of the resins is described.
Three‐phase syntactic foams
Authors: Narkis M. , Kenig S. , Puterman M. 
Published: May 2005

AbstractThree‐phase syntactic foams consisting of a close‐packed microballoons bed, binding resin, and air voids are reported. Preparation methods varied from simple dry‐blending with a solid powdery resin‐to‐resin coating of spheres from polymer solutions. By holding the hollow spheres volume fraction constant and at the maximum packing, a property studied was a function of a single variable, namely, resin volume fraction, void content or density. Mechanical properties are reported as function of one of these variables. The temperature effect was investigated on polyimide based foams. The dielectric constant is shown to obey a logarithmic rule of mixtures. Modified modulus‐composition equations are shown to be applicable for prediction of moduli values of the three‐phase systems.
Continuous fiber rearrangements during the molding of fiber composites. II. Flat cloth to a rounded cone
Authors: Robertson R. E. , Hsiue E. S. , Yeh G. S. Y. 
Published: May 2005

AbstractThis report is the second in a series in which we attempt to develop rapid computational procedures for determining the rearrangement of continuous fibers that occurs during the molding of fiber composite components from flat precursors. This report considers the shaping of a balanced cloth into a cone with a rounded top. The numerical procedure developed predicts that a cloth can be shaped into rounded cones with all but the smallest cone angles without wrinkling. The predictions are compared with experiment for a particular cone angle, and various parameters connected with the shaping calculation are discussed.
Electrostatic phenomena and molecular motion at interfaces of glass/polymer composites
Authors: Stupp S. I. , Weldert S. C. 
Published: May 2005

AbstractA boundary zone of filler‐affected polymeric network is a possible element in the microstructure of composites. The intensity of adsorption potentials for polymeric material on the filler and therefore its surface energy should be an important variable in boundary zone properties. This work has involved the modification of surface energy in a glass filler material through the introduction of externally induced electrostatic charge that is through the creation of a ‘synthetic’ zeta potential on filler particles. The interactions of charged and uncharged glass surfaces with a polymeric matrix were studied by thermally stimulated discharge (TSD), and also by contact angle measurements. The experimental system studied was an aluminosilicate glass as the filler material, and poly(tetraethylene glycol dimethacrylate) as the organic matrix. Contact angle measurements revealed enhanced wettability for the matrix‐forming monomer on glass surfaces charged negatively by electric fields. TSD analysis was also carried out on pure polymer, and composite materials containing either uncharged or bipolar filler particles (particles exposed to an external electrical potential). TSD spectra suggest a suppressed level of molecular motion in composites with fillers of high electrostatic surface energy. Also, activation energies calculated from TSD data are higher in bipolar filler composites. The higher activation energies are consistent with the possibility that a less mobile interfacial zone polymerizes around higher surface energy filler particles.
The relationships between mixing and properties of filled polymers and foams
Authors: Lee Biing‐Lin 
Published: May 2005

AbstractThe increased utilization of reinforced polymeric blend composite materials has prompted renewed interest in mathematical models which can explain or predict the characteristics of processing and the properties of composite materials in terms of the properties and concentration of the components. As a first step toward developing the rules for multicomponent systems we restrict our attention to the Lee‐Nielsen's model and concepts of two‐component systems with particulate inclusions embedded in a continuous matrix. The following property‐mixing relationships are then discussed: (1) reinforcement of uncured and cured rubber composites; (2) thermal expansion of polymer composites; (3) elastic modulus, and thermal conductivity of (reinforced) polymeric foam materials; and (4) heat buildup of rubber composites. Some important concepts and principles which have evolved from our experimental attempts at correlating the behavior of heterogeneous multiphase polymer materials are also discussed.
Mechanical characterization of the interfacial strength of glass‐reinforced composites
Authors: Koenig Jack L. , Emadipour Hamid 
Published: May 2005

AbstractA mechanical test system using a monofilament pullout technique has been utilized to investigate the interfacial bond strength of glass monofilament‐epoxy resin composites. The factors influencing the interfacial strength and hydrothermal stability of the glass monofilament‐epoxy resin composites have been studied including: varying the amount of thickness of the N‐2‐aminoethyl‐3‐aminopropyl trimethoxysilane (AAPS) coupling agent layers between the two substrates of the composite; the debonding effect of moisture and heat as the result of long term exposure; and the partial removal of the deposited silane coupling agent on glass by water, prior to composite preparation. It is found that a critical amount of the bifunctional silane coupling agent is necessary to improve the mechanical strength and hydrothermal stability of the composite interface. Partial removal by washing of the deposited aminosilane on glass, prior to composite preparation, irrespective of its original thickness, enhances the interfacial strength of the composite.
Modification of the dynamic damping behavior of epoxy/glass fiber composites via fiber coating with functional latices
Authors: Schlund B. , Lambla M. 
Published: May 2005

AbstractA series of functionalized latices were synthesized using: n‐butyl acrylate (BuA), butyl methacrylate (BuMA), and glycidyl methacrylate (GMA). The particle microstructure was controlled by a sequential addition of monomers. The glass fibers were commercially roll‐coated using a mixture of these latices and amino‐silane. The specimens were filament wound, compression molded, and cured. The effects of the morphology and reactivity of the latices were analyzed in dynamic as well as flexural modes. The uniformity of the coating as well as the nature of the latex are responsible for the mechanical behavior of the composites.
Influence of a filler on the fracture of a highly crosslinked polymer
Authors: Kalnin M. , Turner D. T. 
Published: May 2005

AbstractGlassy composites were made by photopolymerization of a dimethacrylate paste containing silanated silicate particles (up to 50 μm). Minimum values of Vickers hardness number, stiffness, and yield stress were found for volume fractions of the filler in the range 0.03 to 0.05. Generally fracture surface morphology resembled classical results for inorganic glasses. In addition, tracks and features were observed of the kind reported previously for highly crosslinked organic glasses. Such morphology has been attributed to fortuitous changes in direction of the principal tensile stress just ahead of the crack tip. In the present work it was found that single tracks and features were associated with individual filler particles. This observation is consistent with the expectation that individual particles would act as stress concentrators and thereby serve to change the direction of the principal stress. Furthermore, stress concentration may be invoked to account for the minimum in mechanical properties but dewetting might also be involved.
Effect of fiber misorientation on the tensile strength of compression molded continuous fiber composites
Authors: Mallick P. K. 
Published: May 2005

AbstractResin cross‐flow during compression molding of unidirectional sheet molding compound composites, such as CSMC and XMC, may cause severe misorientation of the continuous fibers in the outer layers. The extent of fiber misorientation depends on the type of molding compound, the length of cross‐flow, and the location of the charge in the mold. The tensile strength is reduced in the direction of cross‐flow with decreasing mold surface coverage. However, since severe fiber misorientation is generally restricted to the outer layers, increasing the number of plies improves the tensile strength to the level observed with little or no misorientation.
Acoustic emission during irreversible deformation in short fiber reinforced poly(vinyl chloride) composites
Authors: Yuan J. , Hiltner A. , Baer E. 
Published: May 2005

AbstractAcoustic emission (AE) during irreversible deformation in short glass fiber reinforced poly(vinyl chloride) (PVC) composites was studied using a piezoelectric crystal transducer. Compared to the well‐coupled composites, many more AE events were observed during tensile deformation in the poorly‐coupled composites, presumably due to failure at the fiber‐matrix interface. No fiber fracture was detected in the tensile tests for either well‐coupled or poorly‐coupled composites. Irreversibility of acoustic emission was observed in repeated tensile loading experiments. Unlike PVC, the short fiber composites fractured during stress relaxation at 1 percent elongation. Studies of acoustic emission behavior during stress relaxation indicated that interfacial debonding is a time‐dependent process. Relaxation fracture time was strongly increased by chemical coupling at the interface.
Quantitative estimation of matrix‐filler interactions in ferrite‐filled styrene‐isoprene‐styrene block copolymer systems
Authors: Shenoy A. V. , Saini D. R. 
Published: May 2005

AbstractQuantitative estimation of matrix‐filler interaction in highly loaded ferrite filled Styrene‐isoprene‐styrene block copolymer has been attempted through dynamic viscoelastic melt studies. A correlation between the interaction parameter in the melt state and that in the solid state at comparable frequency of deformation has been shown to exist so that the matrix‐filler affinity at any temperature of interest can be estimated. Such a correlation eliminates the need for generating solid state dynamic data in order to check matrix‐filler compatibility as the results obtained in the melt could be extrapolated to the behavior in the solid state.
The influence of velocity on the impact strength of glass reinforced polypropylene
Authors: Golovoy A. 
Published: May 2005

AbstractThe influence of impact velocity, between 1 and 8.7 meters per second (m/s) (2.2 to 19.5 mph), on the impact behavior of polypropylene, reinforced with 20 volume percent continuous glass fibers, was investigated in a 3‐point bend test at 21 °C. The ratio of specimen span to thickness, which has a profound effect on the observed results, was varied between 5.3 and 26. An attempt to apply simple beam theory for the analysis of the initial specimen response to the high loading rate was successful, except for the lower than expected values of shear modulus. The stress to break and the tensile and shear moduli were found to increase along with velocity. The dependence of impact energy on velocity was observed to be affected by the span to thickness ratio: a positive dependency was observed at low ratios and none at high ratios. This is different from the negative dependency reported for polypropylene reinforced with short fibers, and is attributed to the influence of the continuous glass fibers on the impact behavior of the composite.