bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic emission in single filament carbon/polycarbonate and Kevlar®/olycarbonate composites under tensile deformation
Authors: Ma B. T. , Schadler L. S. , Laird C. , Figueroa J. C. 
Published: May 2005

AbstractAn analysis of envelope signals of acoustic emission (AE) produced from carbon/polycarbonate and Kevlar®/polycarbonate composites undergoing tensile deformation has been carried out to identify the sources of emission. The Kaiser effect was reproduced to validate the AE technique. Two different fiber failure mechanisms, i.e., fiber fracture and fiber degradation in Kevlar®/polycarbonate composite have been identified. A one‐to‐one correspondence between acoustic emission signals and fiber fracture and degradation has been established. It is shown that the critical length of the fiber, evaluated by using acoustic emission signals, is helpful in understanding the fracture behavior of the composites, as affected by surface treatments of the fibers.
Stiffness and thermal expansion predictions for hybrid short fiber composites
Authors: Camacho Carolyn W. , Tucker Charles L. , Yalvaç Selim , McGee Robert L. 
Published: May 2005

AbstractA model is developed to predict thermal expansion coefficients and elastic moduli of multi‐component (hybrid) composites. The model includes the influences of fiber aspect ratio; isotropic and anisotropic fiber materials; planar, three‐dimensional or arbitrary fiber orientation; hollow and solid spherical reinforcements; and voids. The first step in the procedure is to predict the properties of an aligned‐fiber single‐reinforcement composite for each reinforcement type. Various micro‐mechanics approaches are used, depending on the type of reinforcement. A simplified version of Lee and Westmann's theory is found to work well for hollow spherical reinforcements. Performing an orientation average accounts for the spatial orientation of each reinforcement, then an aggregate averaging procedure combines the single‐reinforcement properties to model the hybrid. Predictions of the model compare favorably to experimental elastic and thermal properties of short fiber/hollow sphere composites designed for very high speed integrated circuit (VHSIC) board applications.
Stamping rheology of glass mat reinforced thermoplastic composites
Authors: Davis S. M. , McAlea K. P. 
Published: May 2005

AbstractGlass mat reinforced thermoplastics (GMTs) offer a useful combination of mechanical properties and formability. In principle, these composites may be based on any thermoplastic matrix. In practice, matrix selection is limited because of its impact on the manufacturing and compression molding processes. In this work an isothermal squeezing flow technique is used to determine the apparent biaxial extensional viscosities of polycarbonate, polybutylene terephthalate, and polypropylene‐based GMTs. Experimental load‐deformation data are interpreted by treating the GMTs as viscous, incompressible Newtonian fluids. Two primary effects are observed: (1) the composites appear to strain harden as they are deformed, and (2) GMT apparent biaxial extensional viscosities correlate with the high rate of deformation shear viscosities of the matrices. A mechanism that explains the second result is proposed.
A finite element/control volume approach to mold filling in anisotropic porous media
Authors: Bruschke M. V. , Advani S. G. 
Published: May 2005

AbstractMold filling in anisotropic porous media is the governing phenomena in a number of composite manufacturing processes, such as resin transfer molding (RTM) and structural reaction injection molding (SRIM). In this paper we present a numerical simulation to predict the flow of a viscous fluid through a fiber network. The simulation is based on the finite element/control volume method. It can predict the movement of a free surface flow front in a thin shell mold geometry of arbitrary shape and with varying thickness. The flow through the fiber network is modeled using Darcy's law. Different permeabilities may be specified in the principal directions of the preform. The simulation permits the permeabilities to vary in magnitude and direction throughout the medium. Experiments were carried out to measure the characteristic permeabilities of fiber preforms. The results of the simulation are compared with experiments performed in a flat rectangular mold using a Newtonian fluid. A variety of preforms and processing conditions were used to verify the numerical model.
Compressibility and relaxation of fiber reinforcements during composite processing
Authors: Kim Young Roak , McCarthy Stephen P. , Fanucci Jerome P. 
Published: May 2005

AbstractIn many reinforced composite manufacturing processes it is necessary to compact the fiber materials to obtain the desired fiber/resin ratio in the finished part. Detailed knowledge of applied surface force versus material fiber volume is particularly important in processes such as pultrusion, resin transfer molding, and compression molding. The force required to compact a stack of reinforcing material is strongly dependent on the type of fiber used and its material form. Complicated interactions are possible, particularly when mixtures of unidirectional, oriented cloth and random fiber mats are used. This paper will present results of an experimental and analytical investigation of the response of various dry reinforcing materials subjected to compressive forces applied normal to their principle plane. Experiments were conducted by applying up to 8.6 MPa normal force to thick stacks of E‐glass, graphite cloth, mat and unidirectional material and combinations of two different fiber orientation. Pressure versus fiber volume data were generated for both individual materials and various combinations. Experimental results were compared to analytical predictions. Data showed that the force versus deformation is very strongly dependent on the details of the fiber form or forms being used. There is structural relaxation during fiber compression. Relaxation is very related to fiber orientation, span length, and fiber breakage during compaction. Relaxation behavior decreases with fiber alignment. Random mats and 0/90 cloth show much more relaxation than unidirectional fibers. Data of relaxation is very well fitted with a Maxwell‐Wiechert viscoelastic model.
Real time cure monitoring of composite structures using the techniques of mechanical impedence analysis
Authors: Jang B. Z. , Hsieh H. B. , Shelby M. D. 
Published: May 2005

AbstractA dynamic mechanical apparatus, based on the concept of mechanical impedance analysis (MIA), was constructed for real‐time cure monitoring of composites. The frequency response function (FRF), in terms of the inertance, impedance or admittance value, can be obtained from the ratio of the Fourier Transforms of excitation and response signals. Spectra during curing of several different kinds of composite materials were obtained with the Fast Fourier Transform spectrum analyzer while the material was continually excited with a random input generated by an electro‐magnetic shaker. The dynamic properties, such as storage modulus (E′) and loss tangent (tan δ), of the composite can be obtained from the FRF spectra as a function of cure time and temperature. Variations of the inertance spectra with cure time, reflecting the changes in the dynamic mechanical properties, for the composite materials under various isothermal cure conditions are discussed. Optimal cure cycles of a new resin can be determined by characterizing the phase transformation of the material, which can be identified from the MIA measurement results. The MIA technique is found to be a sensitive and direct means for monitoring the overall cure state of composites. The signals obtained can be integrated in real‐time in a closed‐loop feedback control system for composite fabrication.
Dynamic mechanical analysis of thermoplastic composites and resins
Authors: Scobbo J. J. , Nakajima N. 
Published: May 2005

AbstractThe anisotropy of continuous fiber thermoplastic composites limits the number of geometries that can be employed effectively in dynamic mechanical analysis (DMA). Therefore, a Mechanical Energy Resolver, developed for use with elastomers, was modified with a bending fixture using a cantilever beam sample geometry and a high temperature oven. The bending fixture allows determination of composite transition temperatures. Based upon the simple geometry, one can also determine elastic moduli. This test scheme can be coupled with simple shear DMA on melts to determine neat resin properties, including solidification temperature. Results are presented for several semicrystalline and armorphous thermoplastic/graphite fiber laminates and neat resins.
Low temperature impact properties of long fiber thermoplastic composite molding materials
Authors: Voelker Marvin J. 
Published: May 2005

AbstractFour long fiber thermoplastic resin matrices, nylon 6, polypropylene, polyethylene terephthalate, and styrene maleic anhydride, containing differing amounts of long fiber glass reinforcement, were tested for notched Izod impact strength over the temperature range of 22 to −32°C. The notched impact properties of the long fiber thermoplastic composite molding materials are substantially greater than literature values for short fiber analogues. The fiber dominant performance of the long fiber materials is evidenced by increasing impact values with corresponding increases in weight percent fiber content. No apparent ductile/brittle transition in the fracture mode was observed for the long fiber materials that were tested.
Effects of graphite fiber and epoxy matrix physical properties on the temperature profile in a composite during cure
Authors: Mijović Jovan 
Published: May 2005

AbstractAn investigation was carried out into the effects of graphite fiber and epoxy matrix physical properties on the temperature profile in their laminates during cure. An accurate prediction of the temperature profile within a composite is of paramount importance in determining the processing conditions. In this study, a model for the temperature profile was established first. Then, three physical parameters of composites that change during cure, namely, density, heat capacity, and thermal conductivity, were varied in magnitude, and the ensuing effect on the temperature profile was examined. The range of their variation was based upon the values measured in our laboratory as well as those reported in the literature. Changes in the neat resin thermal conductivity were found to significantly influence the temperature profile.
Crosslinking‐property relationships in PMR polyimide composites. Part I
Authors: Pater R. H. , Whitley K. , Morgan C. , Chang A. 
Published: May 2005

AbstractThis study examines for the first time how matrix crosslinking affects the composite physical and mechanical properties of a graphite fiber reinforced PMR polyimide composite during long‐term isothermal aging. Unidirectional composite specimens of Celion 6000/PMR‐P1 were isothermally exposed at 288°C in air for various time periods up to 5000 h. The matrix crosslink densities were estimated from the kinetic theory of rubber elasticity and shifts in the glass transition temperatures (Tgs). TheTg, coefficient of thermal expansion, density, weight loss, moisture absorption, and elevated temperature flexural and interlaminar shear properties were also determined. Several linear relationships were found between the matrix crosslink density and composite physical and mechanical properties. TheTg, initial weight loss and density, and elevated temperature interlaminar shear strength increase with an increase in crosslink density. Conversely, the initial moisture absorption and coefficient of thermal expansion decrease with increasing crosslink density. As expected, the elevated temperature flexural strength and modulus show no direct correlations with crosslink density. Further, after achieving the highest matrix crosslink density, several of the composite properties begin to decrease rapidly. These findings suggest that time‐temperature dependent nature of attaining the maximum matrix crosslinking is closely linked to the onset of the composite property degradation. Though much more work is needed, a fundamental understanding of the relationships between matrix crosslinking and composite physical and mechanical property can provide a scientific basis for the prediction of the extent of composite service life not only for PMR polyimides but also for other thermosetting matrix resins, such as epoxies and bismaleimides.
Chemical resistance of carbon fiber‐reinforced poly(ether ether ketone) and poly(phenylene sulfide) composites
Authors: Ma Chen‐Chi M. , Lee Chang‐Lun , Tai Nyan‐Hwa 
Published: May 2005

AbstractStudies have been conducted to investigate the aircraft fluid and chemical solvent resistance of the carbon fiber‐reinforced poly(phenylene sulfide) (PPS) and poly(ether ether ketone) (PEEK) composites. The solvents and aircraft fluids utilized in this work include hydraulic fluid, paint stripper, JP‐4 jet fuel, methyl ethyl ketone, and methylene chloride. The weight gain of the composites as a function of time is measured. Tensile and flexural strength, thermal behavior, and dynamic mechanical properties of the composites are examined. The alteration of crystallinity change of the composites is investigated by X‐ray diffraction. It is found that paint stripper degraded the mechanical properties of the composites significantly. Furthermore, crystallization enhancement of the low crystallinity composites in the presence of solvents and aircraft fluids is also observed.
A model for determining fiber reinforcement efficiencies and fiber orientation in polymer composites
Authors: Rosenthal Jay 
Published: May 2005

AbstractFiber length contributions to the reinforcement potential in composites have been decoupled from fiber orientation effects with the use of a fiber orientation model. Fiber length efficiency factors and fiber orientation factors are calculated based upon a procedure that requires measuring the composite properties in specified directions relative to a reference direction. The procedure is straightforward and relatively quick compared to the tedious task of actually measuring the fiber length distribution. An example illustrating the utility of the procedure is given and then followed by a discussion qualifying the significance of the factors and the results.
Modification of E‐glass fiber surfaces with polyacrylic acid polymers from an aqueous solution
Authors: Lassas Ann‐Cathrine , Fagerholm Lars E. , Stelound Bengt G. , Näasman Jan H. 
Published: May 2005

AbstractThe research reported in the article focuses on modifying glass fiber surfaces with polyacrylic acid (PAA) compounds. E‐glass fibers were treated with aqueous polyacrylic acid solution. Polyacrylic acid exchanges its protons with the ions present in the glass surface. Hydrolyzed metal cations may form salt complexes with the dissociated polyacrylic acid. Angular dependent electron spectroscopy for chemical analysis (ESCA) demonstrated that the atomic concentrations of aluminum and calcium in the glass fiber surface were constant throughout the analyzed interval. The cation exchange property of glass fiber was studied using direct current plasma (DCP), which showed that both calcium and aluminum ions were extracted by low concentration polycrylic acid solutions. ESCA studies of were extracted by low concentrationb polyacrylic acid solutions. ESCA studies of the PAA‐treated glass fiber showed that the amount of PAA of the glass surface increases with increased acid concentration. A broadened and shifted ESCA peak of the carbon (0CO) indicates the formation of salt complexes between the polyacrylic acid and metal ions on the glass surface. Polyacrylie acid was modified by an esterification reaction with glycidyl acrylate (GA) in aqueous solution in order to insert organofuctional groups into the PAA chain.
The effect of microstructure on the elastic modulus and strength of performed and commercial GMTs
Authors: Ericson Mats L. , Berglund Lars A. 
Published: May 2005

AbstractA new technique was used to fabricate performed glass fiber/polypropylene GMTs. The method utilizes thermoplastic powder and fiber roving in a spray‐up procedure in which a porous perform in fabricated, heated and molded. The objective was to compare the properties of various preformed GMT composition with two commercial GMTs and to relate the mechanical properties to the microstructure of the materials. Preformed GMTs were fabricated with various fiber lengths and with or without a fiber/matrix adhesion promotor. Processing observation, microstructure, tensile creep modulus, and tensile strength of these preformed GMTs are reported. Fiber length and the addition of a fiber/matrix adhesion promotor had generally little effect on the modulus and strength of the preformed GMT. Comparisons with two structurally different commercial GMTs also showed negligible effects on modulus and strength. The major reason for this is suggested to be the inhomogeneities of the materials. The mechanical properties are controlled by local inhomogeneities rather than by the general microstructure of the material. These inhomogeneities arise from the fiber arrangement in the semi‐finished sheet or perform. Since the microstructure of preformed GMT can be controlled, this material is well suited for future studies on the effect of better fiber dispersion.
Effects of PVA concentration and ribbon immersion time on the interfacial shear strength of amorphous metallic ribbon/polypropylene composites
Authors: Sidhu A. S. , Varin R. A. 
Published: May 2005

AbstractThe effect of PVA (polyvinyl alcohol) concentration and the immersion time of the Fe40Ni40B20 ribbon was studied in terms of interfacial shear strength. First, the PVA concentration was constant at 9 wt% while the immersion time of the ribbon is the solution was changed form 20 to 200 h. Second., the immersion time was constant at 144 h while the concentration of the PVA was changed form 1 to 12 wt%. The interfacial shear strength improved only slightly by increasing the immersion time from 20 h (0.55 ± 0.09 MPa) to 100 h (0.86 ± 0.12 MPa). The interfacial shear strength increased sharply form 0.86 ± 0.12 MPa at 100 h of immersion time to 3.02 ± 0.66 MPa at 144 h of immersion time. After 144 h of immersion, the interfacial shear strength almost leveled off (2.97 ± 0.26 MPa) at 200 h of immersion. The surface of the polypropylene (PP) after pullout and just before the ribbon fracture was studied with a scanning electron microscope (SEM). The low interfacial shear strength of composites immersed for less than 100 h is related ot the insufficient coating on the ribbon and a lack of the well developed interfacial zone. This is manifested by the presence of circumferential bands and impression from rough marking of the ribbon contact side left on the PP surface. The presence of parabolic markings and growth of spherulites on the PP surface may explain the higher interfacial shear strength observed at longer immersion times in the PVA, which suggests the existence of the well developed interfacial zone between ribbon and the PP matrix. The effect of PVA concentration on interfacial shear strength is almost similar to the effect of immersion time.
Wilhelmy plate studies of carbon fiber/viscous fluid systems
Authors: Giannotta G. , Morra M. , Occhiello E. , Garbassi F. , Nicolais L. , D'amore A. 
Published: May 2005

AbstractThe use of Wilhelmy plate techniques for studying the interactions of fibers with fluids of variable viscosity is discussed. The influence of hydrodynamic effects of force (F) VS. DEPTH (z) plots is interpreted on the basis of surface tension‐independent added terms of the constitutive equation of the Wilhelmy experiment. Wetting experiments using pseudoplastic fluids (polyethyleneglycol/water solution) show that viscoelasticity is indeed important in the interpretation of Wilhelmy plate experiments. The comparison of wetting experiments performed on untreated and plasma‐treated carbon fibers showed that at low stage speed and fluid viscosity, surface chemistry and morphology determines contact angles. At higher stage speeds and viscosities and advancing and receding angles are affected by surface chemistry‐independent and hydrodynamics‐dependent added contributions.
Empirical relations of the mechanical properties of polyamide 6 reinforced with short glass fibers
Authors: Ularych F. , Sova M. , Vokrouhlecḱy J. , Turčić B. 
Published: May 2005

AbstractThe dependence of the mechanical properties on the length of reinforcing fibers in hydrolytic polyamide 6 (PA 6) Matrix was studied. The fibers create a polydisperse system and the fiber distribution can be expressed by the Tung distribution function. Modulus, tensile strength, and also impact strength measured on test pieces seem to be a linear function of the part of fiber length population (percentile) representing the reinforcing fibers longer than 200 μm (value P2). These were determined not only on test pieces but also in starting pellets. The mutual relations between the individual mechanical properties seem to be linear as well. Consequently, the mechanical properties of these PA 6 composites can be estimated from the known distribution of fiber lengths in pellets and from the P200values, without preparing and testing the test pieces. The fiber length distribution in pellets of the composite can be estimated from the values of mechanical data (modulus, strength, impact strength) measured on test pieces.
Energy loss partitioning during ballistic impact of polymer composites
Authors: Zee Ralph H. , Hsieh Chung Y. 
Published: May 2005

AbstractThe objective of this study is to determine the energy dissipation processes in polymer‐matrix composites during impact of ballistic projectiles. These processes include heat, fiber deformation and breakage, matrix deformation and fracture, and interfacial delamination. In this study, experimental measurements were made, using specialized specimen designs and test methods, to isolate the energy consumed by each of these processes during impact in the ballistic range. Using these experiments, relationships between material parameters and energy dissipation were examined. Composites with the same matrix but reinforced with Kevlar, PE, and graphite fabric were included in this study. These fibers were selected based on the differences in their intrinsic properties. Matrix cracking was found to be one of the most important energy absorption mechanisms during impact, especially in ductile samples such as Spectra‐900 PE and Kevlar‐49 reinforced polymer. On the contrary, delamination dominated the energy dissipation in brittle composites such as graphite reinforced materials. The contribution from frictional forces also investigated and the energy partitioning among the different processes evaluated.
Effect of viscosity on the electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture
Authors: Li Lin , Chung D. D. L. 
Published: May 2005

AbstractThe viscosity of thermoplastics above Tg was found to greatly affect the room temperature electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture, while the mechanical properties are essentially not affected. The electrical resistivity decreased and the electromagnetic interference shielding effectiveness increased with increasing viscosity, as shown by using (i) the same filler, namely nickel particles, in polyimidesiloxane and polyether sulfone, and (ii) the same filler and matrix at different composite molding temperatures. This effect is attributed to the flow of the low viscosity thermoplastic particles during composite fabrication tending to disturb the connectivity of the filler particles achieved prior to heating.