bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composites containing glass spheres and fibers: II tensile, flexural, and shear strengths
Authors: Dai S. R. , Piggott M. R. 
Published: May 2005

AbstractTensile, flexural, and shear tests on glass fiber‐polyester pultrusions containing glass spheres show that the spheres reduce the tensile strengths when both rigid and flexible polyesters are used, but some increase in flexural strength is obtained with the flexible resins. Small additions of spheres increased the shear strengths, but for sphere volume fractions greater than about 0.2, the shear strength declined. A silane coupling agent on the spheres increased the strength of the rigid resin composites, but had little effect with the flexible resin. Some of the results could be due to the lack of straightness of the fibers caused by the presence of spheres having diameters greater than the fiber diameter. However, when the fibers were not present, the sphere filled matrices showed very diverse behavior. The results presented here indicate that even in the absence of fibers, simple models are unlikely to be successful in explaining the properties.
Effect of glass fiber length on the creep and impact resistance of reinforced thermoplastics
Authors: Silverman Edward M. 
Published: May 2005

AbstractImpact and flexural creep testing were conducted at temperatures between −22°F (−30°C) and 250°F (121°C) to evaluate and compare the end‐use performance of continuous long glass fiber‐reinforced thermoplastic sheet composites to that of short glass fiber‐reinforced thermoplastics. The matrices studied consisted of amorphous (polycarbonate and acrylonitrile‐butadiene‐styrene) and semicrystalline (polypropylene) polymers. Data were obtained from both injection‐molded specimens (short fibers), and from specimens machine‐cut from compression‐molded test panels (continuous long fibers). The creep results of this study demonstrated that continuous long fibers are more efficient than short fibers in reinforcing the thermoplastic matrices, resulting in enhanced load‐bearing ability at elevated temperatures. The addition of continuous long glass fibers to the thermoplastic matrices led to a significant increase in the notched Izod impact strengths between the temperatures of −22°F (−30°C) and 77°F (25°C), and only slight improvement in the drop‐weight impact strengths. The lack of correlation between notched Izod impact and drop‐weight strengths is largely due to the difference in crack propagation and fracture initiation energies. Results of the Rheometrics instrumented impact test indicated a higher total fracture energy for the long glass‐reinforced thermoplastic sheet composites than for the short glass‐reinforced injection‐molded thermoplastics. The decreased ease of crack propagation in thermoplastic sheet composites is associated with the high energy‐absorbing mechanisms of fiber debonding and interply delamination. The results of this study point to the significant property improvement of continuous long fibersvs.short fibers. The creep strength of short fiber‐reinforced thermoplastics are greatly affected by the nature of the stress transfer which in turn is influenced by the critical fiber length and temperature, which is not the case for the long fiber‐reinforced thermoplastic sheet composites. Long fibers dramatically increase the impact resistance of thermoplastics. The retention of toughness at low temperatures coupled with elevated temperature performance greater than similar short glass fiber‐reinforced thermoplastics effectively extends the capabilities of thermoplastic sheet composites at both temperature extremes.
A model for resin flow during composite processing: Part 1—general mathematical development
Authors: Dave R. , Kardos J. L. , Duduković M. P. 
Published: May 2005

AbstractA generalized three‐dimensional model for resin flow during composite processing has been developed. The model is based on a theory of consolidation and flow through a porous medium, which considers that the total force acting on a porous medium is countered by the sum of the opposing forces, including the force due to the spring‐like effect of the fiber network and the hydrostatic force due to the pressure of the liquid within the porous medium. The flow in the laminate is described in terms of Darcy's Law for flow in a porous medium, which requires a knowledge of the fiber network permeability and the viscosity of the flowing fluid. Unlike previous resin flow models, this model properly considers the flows in different directions to be coupled and provides a unified approach in arriving at the solution. Comparison of numerical solutions with the closed form analytical solution shows good agreement. Resin pressure profiles show that the pressure gradients in the vertical and horizontal directions are not linear, unlike the assumption of linearity made in several previous resin flow models. The effects on the resin pressure of both linear and nonlinear stress‐strain behavior of the porous fiber network were considered. The nonlinear behavior simulates a rapidly stiffening spring and the resin pressure decreases much more rapidly after a given initial period compared to the linear stress‐strain behavior.
Thermal characterization of a bis‐maleimide/bis‐cyanate/epoxy thermosetting resin for composites
Authors: Gotro J. T. , Appelt B. K. , Papathomas K. I. 
Published: May 2005

AbstractThe thermosetting resin investigated here was a mixture of bis‐maleimide and bis‐cyanate, frequently referred to as BT (bis‐maleimide triazine). Triazine is the reaction product of the cyclotrimerization of bis‐cyanate during curing. For circuit board applications, a brominated epoxy resin was blended with BT to impact flame resistance. Resin cure was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated cell infrared spectroscopy, and dynamic mechanical analysis). The ultimate glass transition temperature was found to be 240°C, which could only be obtained using cure temperatures above 225°C. At lower temperatures, the reaction does not reach full conversion, since the glass transition temperature of the curing network equals or slightly exceeds the cure temperature. Differential scanning calorimetry (DSC) indicates a minimum of two separate reactions. Fourier transform infrared spectroscopy provided more detailed information on the crosslinking reactions during cure. The onset of cyclotrimerization was found to start at 150°C, correlating with one of the peaks in the DSC. At higher temperatures, the epoxide reacts with the cyanate functionality forming oxazoline ring structures. It was not possible to unambiguously assign the origins of the high temperature peaks in the DSC. These high temperature peaks may be attributed to several reactions, including epoxy homopolymerization and polymerization of bis‐maleimide. The high temperature reaction mechanisms warrant further investigation.
Fiber orientation and its effect upon thermoelastic properties of short carbon fiber reinforced poly(etheretherketone) (PEEK)
Authors: Bozarth M. Jean , Gillespie John W. , McCullough Roy L. 
Published: May 2005

AbstractExperimental and analytical techniques are employed in the present study to investigate the influence of microstructure on thermoelastic properties of short carbon fiber reinforced poly(etheretherketone). The test specimen geometry is an edge gated, injection molded dogbone tensile bar. Typical of injection molded structures, three distinct layers of fiber orientation were discernable through the sample thickness. The thermoelastic properties of the surface layer (machined from the specimen) are measured for direct correlation with a micromechanics model. In addition to measuring the volume fractions and constituent properties, microstructural features such as fiber aspect ratio and the process‐induced fiber orientation distribution are quantified. Correlation of experimental data with micromechanics model predictions is found to be quite good.
Experimental and analytical procedures for flow dynamics of sheet molding compound (SMC) in compression molding
Authors: Kau Hua‐tie , Hagerman Edward M. 
Published: May 2005

AbstractA package of procedures have been developed to collect and analyze the response of dynamic variables such as pressure, temperature, and mold separation during the compression molding of Sheet Molding Compound (SMC). From the dynamic responses, the molding process was found to consist of two regions: the flow and the subsequent curing reaction region. With an R‐25 formulation and a mold closing rate of 30 mm/s, these two regions are well separated and the average flow time is not significantly affected by the maturation time for the material up to 30 days. Several mechanical parameters were estimated based on relatively simple flow models. The relationship between the press force, mold separation, and mold closing rate is found to be sensitive to the restrictions of the flow.
Cryogenic failure mechanisms of fiber‐epoxy composites for energy applications
Authors: Jang B. Z. , Lieu Y. K. , Chang Y. S. , Hwang L. R. 
Published: May 2005

AbstractFiber‐reinforced composites used in the production, storage, and transport of energy are often exposed to extreme environments such as cryogenic temperatures and/or nuclear radiation. The fraction resistance of composites subjected to these conditions are of fundamental interest. A study was undertaken to examine the effects of Gammaradiation on the structure and properties of fibers, matrix and their interfacial bonding in terms of their influence on composite failure mechanisms. Also thermomechanical analysis was conducted to estimate the residual thermal stresses due to differential thermal expansion coefficients both between fiber and matrix and between two laminae. Results indicate that the impact energy of a composite laminate could be increased by 100 percent by immersing the specimen in liquid nitrogen for only five min. Samples impact‐tested at cryogenic temperatures were found to possess a great degree of delamination and crack bifurcation. Thermomechanical analysis and SEM investigation both reveal that microcracking and small‐scale delamination are promoted by differential thermal contraction. Such effects could be responsible for the observed crack branching and delamination phenomena during impact loading. Although under certain circumstances the Gammaradiation may yield a small increase in fracture resistance it generally degrades the cohesive strength of the matrix and reduces the interfacial bonding between fiber and matrix. Results of a mechanical and microscopic analysis are presented and discussed.
Cellulose fiber‐polyester composites with reduced water sensitivity (2)—surface analysis
Authors: Hua Li , Flodin Per , Rönnhult Tore 
Published: May 2005

AbstractThe water absorption of cellulose fibers has been reduced after the cellulose surface was treated by mono‐ ordi‐methylomelamine(DMM) resin. The wet strength of cellulose‐polyester composites was also enhanced considerably. Scanning electron microscopy, transmission electron microscopy, and electron spectroscopy for chemical analysis were used as the tools for surface analysis in this study. The surface composition and micro morphology have been characterized. Qualitative and semiquantitative results have been obtained for the cellulose fiber surfaces treated with DMM.
The effect of sand surface treatment on sand‐filled composites
Authors: Rodriguez E. L. , Newaz G. M. 
Published: May 2005

AbstractSand/unsaturated polyester composites, 50/50 composition by weight, were prepared from sand treated with different silane solutions. N‐2‐aminoethyl‐3‐aminopropyl‐trimethoxy silane (A0700) and 3‐aminopropyltriethoxy silane (A0750) were used. Water and styrene solutions were employed to treat the sand. It was found that A0750 in styrene produced better composites than other surface treatments. As the interfacial bond was improved, the tensile strength and the tensile modulus increased whereas the strain to failure decreased. The acoustic emission data was a function of the sand surface treatment where a better interfacial bond resulted in more acoustic activity. Dynamic mechanical analysis showed that the interfacial bond affects the dynamic shear modulus, the loss shear modulus, and the damping of the sand‐filled composites. The glass transition temperature (Tg) of the composite was also affected by the surface treatment. The thermogravimetric analysis did not show a well‐defined trend between the decomposition temperature and the surface treatment.
Interfacial adhesion between ionic copolymers and high‐modulus surface‐treated carbon fibers
Authors: Belfiore Laurence A. , Shah Rakesh J. , Cheng Chihmin 
Published: May 2005

AbstractHigh‐modulus carbon‐fiber‐reinforced thermoplastic composites typically fail at the interface due to poor adhesion between fiber and matrix. To increase interfacial strength, the research described herein focuses on modifying the fiber surface (via high‐temperature acid treatment or zinc electrolysis) to facilitate chemical functional groups on the fiber that might increase fiber‐matrix inter‐actions. The thermoplastic matrix materials used in this study were random copolymers of ethylene and methacrylic acid in which the carboxyl groups in the methacrylic acid segments were neutralized with either sodium or zinc counterions. Mechanical tests were performed to determine the macroscopic effects of fiber pretreatment on the ultimate mechanical properties of the composites. Fabrication was designed such that fiber‐matrix separation provides the dominant contribution to mechanical gracture. Composites containing fibers treated with nitric acid, or a mixture of nitric and sulfuric acids exhibit a 20 to 25 percent increase in transverse (tensile) fracture stress relative to composites fabricated with as‐received fibers. Scanning electron microscopy of the fiber‐matrix interface at fracture allows one to “zoom‐in” and obtain qualitative details related to adhesion. Fracture surface micrographs of the above‐mentioned acid‐treated fiber‐reinforced composites reveal an increase in the amount of matrix material that adhered to the fiber surface relative to the appearance of the fracture surface of composites fabricated with as‐received fibers. The presence of acid functionality in the matrix, rather than the divalent nature of the zinc counterions, produces the largest relative enhancement of transverse (tensile) fracture stress in the above‐mentioned composites containing surface‐treated carbon fibers.
Analytical solutions for fiber orientation in 2‐D flows of dilute suspensions
Authors: Eduljee R. F. , Gillespie J. W. 
Published: May 2005

AbstractAnalytical solutions for fiber orientation in dilute solutions are presented for both 2‐D planar and axisymmetric flow. The viscosity is assumed to be independent of position along the flow direction, but varies through the thickness of the mold cavity. For the particular case of a laminate of two fluids, an analytical solution is derived. Based upon the assumption that the fluid adjacent to the mold wall exhibits reduced viscosity due to non‐isothermal considerations, the fluid kinematics simplify, and an analytical solution to Jeffery's orientation equation is derived. Since the fiber orientation analysis is based on Jeffery's equation, it is valid only for dilute suspensions, i.e. for fiber volume fraction < 1/(fiber aspect ratio)2. Qualitatively, the analytical results obtained provide superior correlation with experimental results, indicating that non‐isothermal fluid flow may play an important role in the development of the fiber orientation distribution in the molded component.
Thermal and electrical properties of some epoxy based composites
Authors: Bánhegyi György , Szaplonczay Pál , Frojimovics Gábor , Karasz Frank E. 
Published: May 2005

AbstractThermally stimulated creep compliance, differential scanning calorimetric behavior, thermal degradation, AC dielectric permittivity and loss (between 120 Hz and 100 kHz) and thermally stimulated polarization and aepolarization currents were studied in a cycloaliphatic epoxy resin (B), in a conventional bisphenol‐A‐diglycidyl ester type epoxy resin (C) and in composites consisting of: resin B/wollastonite (B/W), resin B/quartz (B/Q) and resin C/wollastonite (C/W). The filler content was 60 wt%. Resin B exhibited higher Tg and lower rubbery deformability than resin C due to its more compact structure. Fillers reduced the rubbery deformation and thermal expansion and shifted the transition temperatures by a few degrees. The shift depended on the method used. Composites B/W and C/W exhibited higher thermal stability than the corresponding pure resins, while sample B/Q was less stable than resin B. Resins B and C exhibited a low temperature β transition (in the case of resin B a doublet) and a high temperature α or glass transition. AC dielectric losses were fairly similar in samples B and B/W, while the high temperature loss of sample B/Q was determined by a space charge process probably due to the matrix/filler interface. In samples C and C/W the α transition is visible but it is superposed on a strong space charge process due to the resin/electrode interface. Thermally stimulated currents show a behavior qualitatively in agreement with the AC results but the very low effective frequency and the nonlinear field strength dependence of the space charge processes cause some minor differences.
Determination of matrix crystallinity of composites by X‐ray diffraction
Authors: Spahr D. E. , Schultz J. M. 
Published: May 2005

AbstractDetermination of the degree of crystallinity of the matrix of polymer matrix composites by wide‐angle X‐ray diffraction is discussed. An extensive theoretical review is given, and many of the practical difficulties are also discussed. Poly(aryl ether ether ketone)‐carbon fiber composites are used as example materials. It is shown that although wide‐angle X‐ray diffraction is potentially useful for unoriented samples, there are practical and theoretical difficulties in applying the technique to highly oriented materials.
An integrated methodology for optimizing the passive damping of composite structures
Authors: Saravanos D. A. , Chamis C. C. 
Published: May 2005

AbstractA method is presented for tailoring plate and shell composite structures for optimal forced damped dynamic response. The passive damping of specific vibration modes is optimized with respect to dynamic performance criteria including placement of natural frequencies and minimization of resonance amplitudes. The method provides the capability to tailor micromechanics, laminate and structural parameters. Application studies include the optimization of laminated composite beams and composite shells with fiber volume ratios and ply angles as design variables. The results illustrate the significance of damping tailoring to the dynamic performance of composite structures and the effectiveness of the method in optimizing the structural dynamic response.
Polypropylene/low density polyethylene blend matrices and short glass fiber based composites. III: Morphology and fiber orientation
Authors: Ramos M. Arroyo , Belmontes F. Avalos 
Published: May 2005

AbstractThe morphology of short glass fiber reinforced composites based on polypro‐pylene/low density polyethylene (PP/LDPE) blend matrices was investigated by means of an optical microscope as a function of both matrix composition and fiber content. The influence of compounding and processing methods was also studied. The LDPE content hardly affects the morphology of the blends, at least within the range of percentages that have been investigated (5 and 10% by weight). On the other hand, glass fibers obstruct the matrix spherulitic development. The blend morphology is strongly affected by the processing method and the compression molded blends show larger spherulitic size than the injection molded ones. Scanning electron microscopy showed the fiber orientation across the injection molded composites.
Analysis of resin injection molding in molds with preplaced fiber mats. II: Numerical simulation and experiments of mold filling
Authors: Young W. B. , Rupel K. , Han K. , Lee L. James , Liou Ming J. 
Published: May 2005

AbstractThis work presents the results of numerical simulation and experimental visualization of the mold filling process in resin injection molding with preplaced fiber mats. The mold filling experiments were conducted with various mat stacks consisting of continuous random glass fiber mats and bidirectional stitched glass fiber mats. The use of two different mat types in the mat stack created porosity and permeability variations. The effect of these permeability variations was studied by taking flow pressure measurements and observing the progress of the flow front of a non‐reactive fluid filling a clear acrylic mold that contained the reinforcement mat stack. Numerical simulation corresponding to each experiment was also carried out. The numerical results were compared to the experimental measurements.
Processing parameters for consolidating PEEK/carbon fiber (APC‐2) composites
Authors: Colton J. , Muzzy J. , Birger S. , Yang H. , Norpoth L. 
Published: May 2005

AbstractThis consolidation of unidirectional APC‐2 was studied experimentally to determine the effects of processing parameters (pressure, temperature, and number of layers) on resin flow as measured by the Kozeny constant and the bulk modulus. The Kozeny constant obtained was between 0.0205 and 0.107. It was found to depend on the consolidation pressure, temperature, number of layers, and their interactions at a 99% confidence level. The value of the bulk modulus was found to be between 1.21 MPa (175 psi) and 8.58 MPa (1244 psi). It also was found to depend on the temperature, pressure, number of plies, and their interactions at a 99% confidence level. These results show the critical effects of fiber orientation on resin flow during processing.
Processing of poly(ethersulfone)/graphite fiber composites: Thermooxidation, rheology, and consolidation
Authors: Brauman S. K. , Chow A. W. 
Published: May 2005

AbstractThis study relates the formability of thermoplastic poly(ethersulfone) HTA composites to thermooxidative history and rehological behavior. HTA/IM8 graphite fiber performs were prepared under various temperature, time, and environmental (unbagged and vacuum‐bagged) conditions, then consolidated into finished laminates under identical conditions. X‐ray photoelectron spectroscopy and pyrolysis/gas chromatography/mass spectrometry were used to assess chemical degradation, and dynamic mechanical analysis (DMA) was used to evaluate Tg and rheological behavior in the finished laminates. All performing conditions resulted in some degradation of the HTA matrix, the presence of air being especially detrimental. The nature of this degradation is discussed and related to changes in Tg., melt viscosity of the matrix resin, and the extent of consolidation. A new DMA approach to evaluating degree of consolidation is developed and shown to offer considerable promise for quantitative assessment and ranking of composites.
Development of a thin film technique for an amorphous metallic ribbon/thermoplastic matrix composite system
Authors: Sidhu A. S. , Varin R. A. , Wronski Z. 
Published: May 2005

AbstractA thin film method is developed for the fabrication of an amorphous metallic ribbon/PP (polypropylene) matrix composite system. The interfacial shear strength of composites fabricated with thin film is 0.52 ± 0.09 MPa (process B), which is comparable to that of the sandwich method of composite fabrication reported recently. The optical micrographs of the interfacial zone appear to be defect free and there are no visible voids, cracks, or air entrapment during fabrication. This qualitative analysis of the ribbon/matrix interface suggests that thin film can provide a better interfacial bond, a result which is supported by the results of pullouts tests. The composite fabrication time using the thin film method is short, and this method therefore has the potential to produce composites at a high volume fraction of ribbon reinforcements as compared to the sandwich method.