bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat transfer for pultrusion of a modified acrylic/glass reinforced composite
Authors: Sarrionandia Mariasun , Mondragón Iñaaki , Moschiar Stella Maris , Reboredo María Marta , Vázquez Analía 
Published: April 2004

AbstractExperimental values of the temperature on the wall and into the die were obtained for the pultrusion of a modified acrylic resin. The equation of continuity, and energy balance, coupled with a kinetic expression for the curing system, are solved using difference method to calculate the temperature and the conversion profiles in the thickness direction in a rectangular pultrusion die. The effects of the process variables (e.g. pulling rate, die temperature, die thickness and content of fibers) on the performance of the pultrusion are evaluated.
Investigation of interfacial structure of couping agent treated fillers by fourier transform infrared spectroscopy and attenuated total reflection‐FTIR spectroscopy
Authors: Liu Yujuan , Yang Rui , Yu Jian , Wang Kunhua 
Published: April 2004

AbstractThe interfacial structures of fillers treated by coupling agents were studied with FTIR and a Attenuated Total Reflection (ATR)‐FTIR spectrometer. The interfacial interaction was investigated by FTIR, and the nature of interaction was proved to be a chemical bonding, which could not be destroyed by extraction. Using a variable angle ATR technique, the average interfacial layer thickness of filler treated with different amounts of coupling agent was determined. A calibration curve was obtained from these studies to determine the optimal amount of coupling agent for different fillers, which was in agreement with the results of mechanical tests. ATR‐FTIR technique is a convenient method to determine the proper amount of coupling agent in composites.
Effects of processing conditions on the fiber length distribution and mechanical properties of glass fiber reinforced nylon‐6
Authors: Yilmazer Ulku , Cansever Murat 
Published: April 2004

AbstractThe effects of processing conditions on fiber length degradation were investigated in order to produce composites with higher performance. Nylon‐6 was compounded with glass fibers in a twin‐screw extruder for various combinations of screw speed and feed rate. Collected samples were injection molded and Izod impact and tensile tests were performed in order to observe the effect of fiber length on the mechanical properties. Also, by using the extruded and injection molded smaples, fiber length distribution curves were obtained for all the experimental runs. Results show that when the shear rate is increased through the alteration of the screw speed and/or the feed rate, the average fiber length decreases. Impact strength, tensile modulus and tensile strength increase, whereas elongation at break decreases with the average fiber length.
Elastic moduli of particulate composites with graded filler‐matrix interfaces
Authors: Ozmusul M. S. , Picu R. C. 
Published: April 2004

AbstractThe elastic response of plane‐array models of composites reinforced by particles or aligned fibers having graded interfaces with the matrix is analyzed. Such microstructure is representative of a new class of polymer matrix composite materials in which the filler is nanometer‐sized. In such materials, the polymer chains in the matrix are preferentially oriented close to the interface with the relatively rigid fillers, this leading to a graded interfacial layer about each inclusion. The composite elastic moduli are determined based on the properties and geometry of the interfacial graded layer as well as on the moduli of the filler and the matrix, and the volume fraction of filler. Conversion curves are constructed allowing for an equivalence to be established between the present case and that of similar composites without graded interfaces. Based on these conversion curves, standard homogenization algorithms can be applied to determine the overall elastic properties of such composite. The fillers are considered to be stiffer than the matrix, both rigid and of finite stiffness. Results for both sliding and bonded interfaces are presented. The effect of anisotropic material properties in the graded region on the composite moduli is also investigated. The results of the model are compared with published experimental data.
Resin transfer molding of natural fiber reinforced polybenzoxazine composities
Authors: Dansiri Nadsuda , Yanumet Nantaya , Ellis John W. , Ishida Hatsuo 
Published: April 2004

AbstractKenaf fiber is incorporated in a polybenzoxazine (PBZX) resin matrix to form a unidirectionally reinforced composite containing 20 wt% fiber by a resin transfer molding technique. Two types of benzoxazine monomer are synthesized and used as resin mixtures: Benzozazines based on bisphenol‐A/aniline (BA‐a) and phenol/aniline (Ph‐a). The effects of varying BA‐a:Ph‐a ratio in the resin mixture and curing conditions on mechanical properties of pure PBZX resin and kenaf/PBZX composites are studies. The Flexural strength of the pure PBZX resin increases with increasing ratio of BA‐a:Ph‐a, curing temperature and curing time, but the impact strength increases only slightly. PBZX resin has lower water absorption and higher flexural modulus, when compared with unsaturated polyester (UPE) resin. PBZX composites with 20 wt% fiber content have lower flexural and impact strengths, but higher moduli compared with UPE composites with the same fiber content.
Mechanical damage and strain in carbon fiber thermoplastic‐matrix composite, sensed by electrical resistivity measurement
Authors: Mei Zhen , Guerrero Victor H. , Kowalik Daniel P. , Chung D. D. L. 
Published: April 2004

AbstractThe volume electrical resistivity of a unidirectional continuous carbon fiber thermoplastic (nylon‐6) matrix composite was found to be an indicator of strain and damage during repeated loading in the fiber direction. The through‐thickness resistivity irreversibly and gradually decreased upon damage (probably fiber‐matrix debonding) during repeated compression or tension. Moreover, it reversibly and abruptly increased upon matrix damage, which occurred reversibly near the peak stress of a stress cycle. In addition, the resistivity increased reversibly upon tension in every stress cycle, and decreased reversibly upon compression in every stress cycle. On the other hand, the longitudinal resistivity irreversibly and gradually increased upon damage. Moreover, it decreased reversibly upon tension in every stress cycle and increased reversibly upon compression in every stress cycle. The through‐thickness resistivity was a better indicator of damage and strain than the longitudinal resistivity.
Optimal design of multi‐direction composite flywheel rotors
Authors: Gowayed Yasser , Abel‐Hady Faissal , Flowers George T. , Trudell Jeffrey J. 
Published: April 2004

AbstractDesign of composite flywheels made with reinforcement in the hoop and radial directions (Multiple Direction Composites MDC) involves a large multitude of parameters such as those related to the flywheel operation, flywheel geometry, material characteristics, material layup, and stress spatial distribution and values. The problem is further complicated because most design parameters are interactive and because one parameter cannot be optimized independent of the other parameters. Optimum structural design of MDC flywheels using nonlinear optimization via a sequential quadratic programming approach and parametric finite element analysis are used to address this problem. Numerical examples are solved to compare the efficacy of the two approaches.
Reverse piezoelectric behavior of carbon fiber thermoplastic‐matrix composite
Authors: Mei Zhen , Guerrero Victor H. , Kowalik Daniel P. , Chung D. D. L. 
Published: April 2004

AbstractThe reverse piezoelectric effect was observed in the through‐thickness direction of a continuous carbon fiber nylon‐6 matrix composite. The piezoelectric coupling coefficient was 2.2 × 10−6 m/V, as determined up to an electric field of 261 V/m. The effect was largely reversible upon turning off the field and was unaffected by field reversal. It is attributed to the electric dipoles in the nylon‐6 matrix.
Production of leather‐like composites using short leather fibers. II. Mechanical characterization
Authors: Madera‐Santana T. J. , Aguilar‐Vega M. J. , Márquez A. , Vázquez Moreno F. , Richardson M. O. W. , Cruz Machin J. L. 
Published: April 2004

AbstractLeather‐like composites were prepared by addition of chemically modified short leather fibers (SLF) into a plasticized polyvinyl chloride (pPVC) matrix. The fibers were subjected to chemical modification by emulsion polymerization to achieve good interfacial adhesion between SLF and the pPVC matrix. The SLF with chemical modification were obtained from three different reaction conditions where these SLF have different percentages of grafted and deposited PMMA polymer onto the fiber surface. The incorporation of the SLF into the thermoplastic matrix was carried out using a torque‐rheometer and the composites obtained were molded by compression. Tensile and tear mechanical tests were performed on composite samples, and the morphology of the fractured surfaces was analyzed using scanning electron microscopy (SEM). The results show that the incorporation by grafting of polymethyl metacrylate (PMMA) onto the fibers produced a significant improvement of their interfacial adhesion to pPVC, promoting the compatibilization between the fiber surface and matrix. The findings are discussed and interpreted in terms of enhanced adhesion at phase boundaries. Overall, the results confirm that it is possible to produce modified leather composites based on a pPVC matrix, which exhibit relatively high tensile strength, tear resistance and flexibility. These composites are very suitable candidate materials for applications in the footwear industry.
Evaluation of the formability of plastic/Zn22Al/plastic sandwiched structures by gas blowing
Authors: Tsao L. C. , Su T. L. , Chuang T. H. 
Published: April 2004

AbstractFor the manufacturing of electromagnetic interference (EMI) shielding enclosures for portable 3C (computer, communication, and consumer electronics) products, a superplastic Zn22Al thin sheet is inserted in between plastic plates and formed by in‐mold blowing with gas pressure. In order to evaluate the formability of a plastic/Zn22Al/plastic sandwiched structure, free bulging tests are conducted in the temperature range between 135°C and 200°C in an infrared furnace. The results show that the ABS/Zn22Al/ABS sandwiched structure can be free bulged at 150°C with 0.21 MPa of gas pressure at a forming rate similar to that of the monolithic Zn22Al sheet. The PC/Zn22Al/PC sandwiched structure cannot be effectively bulged until the forming temperature is raised to 185°C. The optimized forming condition for PC/Zn22Al/ABS is either at 150°C with a gas pressure of 0.35 MPa or at 165°C and a gas pressure setting of 0.21 MPa. Also, the thickness distributions for Zn22Al and a variety of plastic/Zn22Al/plastic specimens after free bulging at various temperatures with various gas pressures are placed in comparison in this study.
Separation of gelation from vitrification in curing of a fiber‐reinforced epoxy composite
Authors: Bilyeu Bryan , Brostow Witold , Menard Kevin P. 
Published: April 2004

AbstractPrepregs of a mixture of the tetrafunctional epoxy tetraglycidyl 4,4‐diaminodiphenyl methane (TGDDM) and the tetrafunctional amine 4,4'‐diaminodiphenylsulfone (DDS) were characterized with temperature‐modulated DSC (TMDSC) as well as dynamic mechanical analysis (DMA). The baseline shift of the glass transition was separated from the curing exotherm by using temperature‐modulated and step scan DSC temperature scans. Likewise, the baseline shift in heat capacity due to vitrification was isolated using TMDSC isotherms. Using the TMDSC glass transition temperature, degree of conversion, and vitrification results, combined with the gelation data generated from DMA, a time‐temperature‐transformation (TTT) diagram was constructed, providing information necessary for optimization of industrial processing of the epoxy prepreg. Thus, effects of storage, preprocessing, and postprocessing on the overall curing process are taken into account.
Consolidation of carbon fiber laminae during polymer‐matrix composite fabrication, studied by electrical resistance measurement
Authors: Wang Shoukai , Chung D. D. L. 
Published: April 2004

AbstractThe consolidation of carbon fiber epoxy‐matrix laminae during composite fabrication by lamination (involving consolidation, curing and cooling) was found to hastened and to occur to a greater extent by increasing the pressure. The consequence of better consolidation remained after curing and subsequent cooling. A higher pressure resulted in a lower throughthickness resistivity in a composite after curing and cooling. The extent of consolidation was quantitatively described by N/No (the ratio of the number of fiber‐fiber contacts between adjacent laminae at a given time, divided by that at the start of consolidation), which was calculated from the measured through‐thickness electrical resistivity. From the variation of N/No during heating in the process of consolidation, three stages of consolidation were observed. In the first stage, N/No increased very gradually; in the second stage, N/No increased abruptly; in the third stage, N/No increased at a moderate rate.
Relationship between processing and properties of biodegradable composites based on PCL/starch matrix and sisal fibers
Authors: Cyras Viviana P. , Iannace Salvatore , Kenny José M. , Vázquez Analía 
Published: April 2004

AbstractBiocomposites were produced using polycaprolactone and starch as matrix, and sisal fibers as reinforcement. The matrix is a biodegradable commercial product called MaterBi‐Z, which is based on a polycaprolactone and starch system. The relationship between processing conditions and properties is reported. An alkaline treatment was performed in order to improve the adhesion and the compatibility of the fiber with the matrix. The effect of the treatment on the tensile properties and morphology was determined. Fiber content enhances the tensile properties of the biodegradable composite. The experimentally observed tensile properties (modulus and tensile strength) of short sisal fiber reinforced MaterBi‐Z matrix composites with different fiber loading are compared with the existing theories of reinforcement. SEM photomicrographs of the fractured composite surfaces are also analyzed.
Temperature and loading rate effects in the mode II interlaminar fracture behavior of carbon fiber reinforced PEEK
Authors: Berger L. , Cantwell W. J. 
Published: April 2004

AbstractThe combined effect of varying loading rate and test temperature on the mode II interlaminar fracture properties of AS4/carbon fiber reinforced PEEK has been investigated. End notch flexure tests have shown that this thermoplastic‐based composite system offers a very high value of interlaminar fracture toughness at room temperature. Increasing the test temperature leads to a reduction in the mode II interlaminar fracture toughness of the composite, with the value at 150°C being approximately one half of the room temperature value. In contrast, increasing the crosshead displacement rate has been shown to increase the value of GIIcby up to 25%. A more detailed understanding of the effect of varying temperature and loading rate on the failure mechanisms occurring at the crack tip of these interlaminar fracture specimens has been achieved using the double end notch flexure (DENF) geometry. Here, extensive plastic flow within the crack tip region was observed in all specimens. It is believed that the rate sensitivity of GIIcreflects the rate‐dependent characteristics of the thermoplastic resin.
The packing stress of impregnated fiber mats
Authors: Servais Colin , Michaud Véronique , Månson Jan‐Anders E. 
Published: April 2004

AbstractThe parameters affecting the packing stress of fiber mats for melt impregnation, resin transfer molding and compression molding are systematically investigated. An analytical equation based on local bending of fibers, which was previously derived for non‐impregnated networks, is applied to composite mats of dispersed planar bundles impregnated with molten polypropylene. It is shown that many simultaneous mechanisms interact during packing of impregnated bundle mats, in particular when the mats are needled. These include in‐plane bending of the bundles, compaction of the fibers within a bundle, and buckling, slippage or breakage of the out‐of‐plane fibers. In order to identify and decouple these features, aspect ratio of the bundles, lubrication, needling intensity and packing history are varied. A microstructural experiment is also developed to evaluate the extent of bundle spreading. It is found that dispersed fibers or bundles roughly follow the equation based on local bending, but that needled bundle networks deviate from the power law behavior. Three regions were identified. The first is attributed to self‐loading of the mats and to buckling of the out‐of plane fibers. The second region is due to slippage and breakage of the out‐of‐plane fibers and depends on the loading history and on the needling intensity. The third region is due to packing of the in‐plane bundles, which do not really bend, or spread under load, but are locally compressible, owing to misalignment and waviness of the individual fibers forming the bundles. In compression molding, the influence of the in‐plane reorientation of the initially out‐of‐plane bundles on the packing stress is observed.
In situ elevated‐temperature drift spectroscopyof γ‐aminopropyltriethoxysilane as a condensed phase and a coated film on silica surface
Authors: Noobut W. , Koenig J. L. 
Published: April 2004

AbstractIt is the purpose of this study to determine the structure of γ‐amlnopropyltriethoxysilane (APS) on the surface of silica. Diffuse Reflectance spectroscopy (DRIFT) was employed to study the molecular structure of the partially condensed (APS) and Al's‐coated silica at 90°C. The condensed APS and Al's‐coated silica were prepared at the natural pH (10.3) of the APS and in the ambient environment. At room temperature, amino groups of the condensed APS and the APS‐coated silica form the amine carbonate and amine bicarbonate salts. Upon heat treatment, the amino salt structures are eliminated, leaving the amino groups in non‐bonded form.
Flow front measurements and model validation in the vacuum assisted resin transfer molding process
Authors: Mathuw R. , Advani S. G. , Heider D. , Hoffmann C. , Gillespie J. W. , Fink B. K. 
Published: April 2004

AbstractThrough‐thickness measurements were recorded to experimentally investigate the through thickness flow and to validate a closed form solution of the resin flow during the vacuum assisted resin transfer molding process (VARFM). During the VART'M process, a highly permeable distribution medium is incorporated into the preform as a surface layer and resin is inftised Into the mold, under vacuum. During Infusion, the resin flaws preferentially across the surface and simultaneously through the thickness of the preform, giving rise to a three dimensional‐flow front. The time to fill the mold and the shape of the flow front, which plays a key role in dry spot formation, are critical for the optimal manufacture of large composite parts. An analytical model predicts the flow times and flow front shapes as a function of the properties of the preform, distribution media and resin. It was found that the flow front profile reaches a parabolic steady state shape and the length of the region saturated by resin is proportional to the square root of the time elapsed. Experimental measurements of the flow front in the process were carried out using embedded sensors to detect the flow of resin through the thickness of the preform layer and the progression of flow along the length of the part. The time to fill the part, the length of flow front and its shapes show good agreement between experiments and the analytical model. The experimental study demonstrates the need for control and optimization of resin injection during the manufacture of large parts by VARTM.
Prediction of failure and fracture mechanisms of polymeric composites using finite element analysis. Part 1: Particulate filled composites
Authors: Ghassemieh E. , Naseehi V. 
Published: April 2004

AbstractMicro‐mechanical analysis of polymeric composites proves a powerful means for the quantitative assessment of their bulk behavior. In this paper we describe a robust finite element model (FEM) for the micro‐structural modeling of the behavior of particulate filled polymer composites under external loads. The developed model is applied to simulate stress distribution in polymer composites containing particulate fillers. Quantitative information about the magnitude and location of maximum stress concentrations obtained from these simulations is used to predict the dominant failure and crack growth mechanisms in these composites. The model predictions are compared with the available experimental data and also with the values found using other methods reported in the literature. These comparisons show the range of the validity of the developed model and its predictive potential.
Analytical modeling of tensile strength of particulate‐filled composites
Authors: Li Guoqiang , Helms Jack E. , Pang Su‐Seng , Schulz Kurt 
Published: April 2004

AbstractBased on Christen sen and Lo's (11) three‐layer sphere model, a two‐layer built‐in model is proposed to represent particulate‐filled composites. Following Papanico‐laou and Bakos' (14) procedure for a particle embedded in an infinite matrix model and using the rule‐of‐mixtures approach, formulations estimating the tensile strength of particulate‐filled composites are developed. Unlike Fapanicolaou and Bakos' formulations, the formulations developed in the present paper can characterize the effect of particle size, particle size distribution, and particle clustering on the tensile strength of the composites. A reasonable agreement is found between the predicted tensile strength and the experimental results found in the literature. Parameters affecting the tensile strength of particulate‐filled composites are discussed via the calculated results.
Analysis of heat transfer in autoclave technology
Authors: Antonucci Vincenza , Giordano Michele , Inserraimparato Sabato , Nicolais Luigi 
Published: April 2004

AbstractIn autoclave technology, polymer based composites are manufactured under the application of pressure and heat. The heat transferred between the energy carrying fluid and the bag‐composite‐tool element activates exothermic curing reactions, leading to composite consolidation. The convective heat transfer mechanism is the most relevant aspect controlling the rate of chemical and physical transformations associated with composite curing. Moreover, the fluidodynamic regime that results from the interactions between the autoclave and the tool geometry, even if totally predictable in theory, is unattainable in practice. In this study, the heat transfer phenomena occurring during the autoclave manufacturing cycle have been analyzed. The assumption of a negligible through‐the‐thickness thermal gradient led to simplified energy balance equations. In this case, the thermal evolution of the manufacturing elements has been completely determined by two parameters: the global convective heat exchange coefficient, setting the rate of the heat transfer between the autoclave environment and the bag‐composite‐tool element, and the adiabatic temperature rise, establishing the relevance of the polymerization exotherm. A scaling analysis has been performed in order to identify the dimensionless parameters controlling the autoclave process. The developed semitheoretical methodology has been extensively tested by comparison with experimental data from an industrial autoclave.