bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser drilling of liquid crystal polymer composite
Authors: Yue T. M. , Chan K. C. 
Published: April 2004

AbstractThis investigation studies the laser machining behavior of a glass fiber reinforced liquid crystalline polymer (LCP) composite by using two different types of lasers, namely; pulsed Nd:YAG and excimer. A theoretical model is established to predict the maximum depth‐of‐drill of the YAG laser machined holes. Moreover, the effects of the YAG laser output parameters on the geometry and the quality of the machined surface of the hole are discussed. The laser machining characteristics of the composite are compared for the two different types of lasers in terms of laser absorptivity. The results show that the glass fiber reinforced LCP has a higher absorption towards UV radiation than infrared light. Scanning electron microscopy examinations were also conducted to assess the surface quality of the machined holes. In YAG laser drilling, a high pulse energy or excessive pulses caused severe carbonization of the surface, and many cracks formed. On the other hand, excimer laser did not cause any significant carbonization of the surface; however, a large number of voids were found in the process affected zone.
Processability and properties of novel glass‐polymer melt blends
Authors: Otaigbe Joshua U. , Quinn Candace J. , Beall George H. 
Published: April 2004

AbstractDynamic mechanical analysis was used to study the viscoelastic properties of two novel highly filled phosphate glass‐polymer melt blends to accelerate efforts to optimize their melt processing. The melt of one blend was thermally stable while that of the other blend was not, as evidenced by modulus growth over time of the latter. The frequency dependencies of storage and loss moduli for both blends at 400°C showed evidence of incomplete relaxation. Recrystallization, formation of some fibrillar structures within the polymer phase during flow, transesterification of the polymer phase, or interactions between the polymer and glass are thought to be responsible for the observed differences between the viscoelastic properties of the two blends.
The gradient of mechanical characteristics across the thickness of composite laminates after exposure to a low earth orbit environment
Authors: Startsev Oleg V. , Isupov V. V. , Nikishin E. F. 
Published: April 2004

AbstractThis paper deals with a complex investigation of carbon and glass fiber reinforced plastics (CFRP, GFRP) and hybrid composites based on epoxy compositions and used in Salyut‐type spacecraft that had spent up to 1501 days in outer space. The samples with an unprotected surface and the samples exposed to outer space under the different screens have been explored. In the paper, results on thin measurements of dynamic shear modulus, Young's modulus, linear thermal expansion coefficient, glass transition temperature, and microhardness of the carbon plastics KMU‐31, KMU‐41, and glass plastics VPS‐7V are presented. Results show that thermal cycling of composite laminates in space, with a temperature difference of 200 K between the sunlit side and the reverse side, generates the gradient of mechanical properties across the plate thickness. Particular attention is given to the problem of thin layer measurement methodology and to the working out of experimental results. There are requirements for ground simulation research of composite laminates providing the same character of thermal cycling as in a low earth orbit, LEO. Some criteria are suggested for test equivalence, according to the data of dynamic mechanical analysis (DMA), linear dilatometry (LD), and microhardness.
Determination of corner and edge permeability in resin transfer molding
Authors: Sheard J. , Senft V. , Mantell S. C. , Vogel J. H. , Maier R. S. 
Published: April 2004

AbstractResin flow in resin transfer molding may be strongly influenced by small heterogeneities in the fiber preform, such as narrow channels formed by bending and fitting into a mold. An evaluation of preform permeability in these regions of nonuniform packing is presented. The study incorporates an empirical and analytic approach to iteratively determine the permeability in these regions. Flowfront data were recorded for high fiber volume fraction woven fiber preforms. Edge gap width, injection pressure, and fiber volume fractions were varied. The flow front data were compared with numerical simulations to estimate enhanced permeability at the edges. The results indicate that, for high fiber volume fraction preforms, flow in the channel dominates for relatively small (≈ 2 mm) gaps.
Barium sulfate–filled blends of polypropylene and polystyrene: Microstructure control and dynamic mechanical properties
Authors: Hammer Claes O. , Maurer Frans H. J. 
Published: April 2004

AbstractThe microstructure of filled blends consisting of a semicrystalline polypropylene homopolymer (PP) matrix and a polystyrene (PS) dispersed phase with barium sulfate (BaSO4) filler can be controlled by an addition of maleic anhydride‐grafted polypropylene (PP‐g‐MAH) or styrene‐maleic anhydride copolymer (SMA). Scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) in the solid and melt states were the analytical tools used. The filler is occluded at the interface of the polymer phases in the filled blend without PP‐g‐MAH or SMA. The addition of BaSO4 to the PP/PS blend results in a decrease in domain size of the minor polymer phase. The filler is occluded in the PP phase when PP‐g‐MAH is added, while SMA results in the occlusion of the barium sulfate filler in the PS phase. The results of the SEM and the DMA studies were correlated, with indications of a filler network structure with both the PP‐g‐MAH and SMA modifiers. The barium sulfate filler surface has a specific affinity to maleic anhydride copolymers. The BaSO4 filler alone did not have a nucleation effect on the PP; however, in combination with PP‐g‐MAH, a clear nucleation effect was observed.
Production and characterization of innovative carbon fiber–polycarbonate composites
Authors: Caldeira G. , Maia J. M. , Carneiro O. S. , Covas J. A. , Bernardo C. A. 
Published: April 2004

AbstractVapor Grown Carbon Fiber (VGCF)–polycarbonate composites were produced using conventional processing and the performance of the parts thus produced was evaluated. The tensile properties of the composites were only marginally better than those of the nonreinforced polymer, and the impact resistance decreased with the incorporation of the fibers. In an attempt to understand this behavior, the rheological characteristics of the composites were studied, using rotational (steady and oscillatory) and capillary rheometry. A decrease in viscosity with fiber content was observed and explained in terms of poor fiber‐matrix adhesion. Evidence of possible weak fiber structures forming above a critical concentration was also found.
Resin transfer molding (RTM) with toughened cyanate ester resin systems
Authors: Rau A. V. , Srinivasan S. A. , McGrath J. E. , Loos A. C. 
Published: April 2004

AbstractThis investigation explored the feasibility of recently developed toughened cyanate ester networks as candidate materials for high performance composite matrix applications. The resin investigated was a bisphenol‐A cyanate ester toughened with hydroxy functionalized phenolphthalein based amorphous poly(arylene ether sulfone). A series of four toughened cyanate ester resins were generated by varying the concentration and the molecular weight of the toughener. The thermoplastic modified toughened networks exhibited improvement in the fracture toughness over the base cyanate ester networks without significant reductions in mechanical properties or glass transition temperature. Carbon fabric composite panels were manufactured by liquid molding processes (resin transfer molding and resin film infusion) with the untoughened and toughened cyanate ester resin systems. The panels were subjected to physical, impact damage, and fracture toughness tests. The results of physical testing indicate consistently uniform quality, and the maximum void content was found to be less than 2%. The toughened cyanate ester composites exhibited significantly improved impact damage resistance and tolerance compared with hot‐melt epoxy systems. A marked increase in the mode II composite fracture toughness was observed with an increase in the concentration and the molecular weight of the toughener.
Pultrusion die pressure response to changes in die inlet geometry
Authors: Sharma D. , McCarty T. A. , Roux J. A. , Vaughan J. G. 
Published: April 2004

AbstractPultrusion is a process of manufacturing composites that requires a high resin pressure rise in the tapered die inlet region. A sufficiently high pressure rise is important for a good quality pultruded product, thereby necessitating a study of the mechanisms affecting the die inlet pressure rise. Various process control parameters affect the resin pressure rise in the die inlet. The geometry of the tapered die inlet region can have a significant effect on the pressure rise in the pultrusion die. In this study a finite element model was developed to predict this pressure rise as a function of the tapered die inlet geometry. The composite matrix being pultruded was modeled on the assumptions of Darcy's laws for flow in porous media. A Galerkin's weighted residual based finite element technique was used to solve the governing equations. The pressure rise in the tapered inlet region of the die, as well as in the straight portion of the die, is predicted by this finite element model. Circular, parabolic, and wedge shaped die inlets have been modeled to compare their shapes on the resin pressure rise in the pultrusion die. Different angles for wedge shapes, different radii for circular shapes, and different foci for parabolic shapes were modeled to predict the influence of varying key geometrical parameters for each die inlet contour on pressure rise. The finite element model developed provides insight as to how to design the die inlet to produce a suitable pressure rise in the pultrusion die inlet.
Extrusion and mechanical characterization of PVC‐leather fiber composites
Authors: Madera‐Santana Tomás J. , Torres Alberto Campos , Lucero Alfredo Márquez 
Published: April 2004

AbstractEvery year great quantities of chrome tanned leather wastes produced by the footwear and clothing industries are buried or burned. These practices produce several contaminants that are released into the environment. An alternative to disposing of these wastes is to reuse them. In this work, a method to use these wastes as filler in a polymer matrix is proposed. Also, a technique for processing the composite obtained by continuous extrusion is demonstrated. To evaluate this technique, a series of PVC‐leather fiber composites were prepared and extruded through a flat die to produce sheets. The process produced a leather‐like sheet that could be used in several applications. The influence of the filler content on the processability and the final properties of the composite sheets were evaluated. The tests revealed that the sheets are flexible and exhibit sufficient water absorption to be suitable for several applications in the footwear and clothing industry. Finally, the tests show that this composite can be formulated and processed at high productivity levels and at a low cost.
Power issues in the manufacturing and characterization of polymers and composite materials
Authors: Buehler Frédéric U. , Seferis James C. 
Published: April 2004

AbstractDynamic Mechanical Analysis (DMA), although utilized for more than three decades, has been restricted so far to material characterization rather than processing. Recently the importance of power for describing viscoelasticity in prepreg process operations has been demonstrated. This present work views DMA as an integral part of the power analysis of processes. In this study, four types of prepreg were produced under the same power of impregnation utilizing epoxy resins with various PEI contents. Prepregs were tested for compressive and toughness power as well as loss power. Laminates were developed and analyzed by DMA. DMA data was treated according to the established power methodology and compared with the tack power of the original prepreg. Specific compressive power was generally found to increase with increasing storage DMA power, while specific toughness power was found to show the opposite trend. The inverse of power, defined as tolerance, was also investigated. The out‐of‐phase DMA tolerance was found to correlate to loss prepreg power, bringing a deeper understanding to the fundamentals of viscoelasticity formation. This analytical methodology can be applied beneficially to many topics to provide a better understanding of polymers and composites, as well as smart materials.
Crystalline morphology in high‐density polyethylene/paraffin blend for thermal energy storage
Authors: Lee Chang Hyung , Choi Hyeong Ki 
Published: April 2004

AbstractThe durability of high‐density polyethylene (HDPE)/ paraffin blends as a thermal energy storage material was studied by investigation of the seepage behavior of paraffin. The HDPE in the blends serves to prevent paraffin seepage during repeated heating‐cooling cycles; i.e., the HDPE acts as a sealant material. Two representative HDPEs were used for the blends; one was a low molecular weight HDPE (1‐HDPE) and the other was a high molecular weight HDPE (h‐HDPE). Investigation by optical microscopy, scanning electron microscopy and light scattering revealed that the surface area of an injection molded sample in h‐HDPE/paraffin blend had compact spherulites of about 7 μm in radius. On the other hand, the morphology of the coarse spherulite of about 15 μm in radius is observed in the 1‐HDPE/paraffin blend. This crystalline morphological characteristic resulting from the molecular weight difference of the sealant material (HDPE) is responsible for the excellent sealant property of the h‐HDPE/paraffin blend.
Effect of heating on the structure of carbon fiber polyphenylenesulfide‐matrix composite, as studied by electrical resistance measurement
Authors: Mei Zhen , Chung D. D. L. 
Published: April 2004

AbstractHeating and cooling were found to affect the structure of carbon fiber polyphenylenesulfide‐matrix composites, as shown by their effects on the DC electrical resistance of the composite in the fiber direction. Matrix flow during first heating above Tg and thermal stress buildup during cooling in any thermal cycle caused the resistance to increase, whereas isothermal crystallization at 180°C caused the resistance to decrease. Thermal stress buildup was reversible upon thermal cycling. Prior annealing at 180°C diminished the matrix flow because of improved fiber‐matrix bond, and it increased the matrix crystallinity. Annealing at 180°C for 15 h or more was sufficient to eliminate the matrix flow.
Mechanical properties of parts manufactured from prestaged thermosetting towpreg
Authors: Beck R. W. , Colton J. S. 
Published: April 2004

AbstractA prestaging process consisting of passing thermoset towpreg through a tunnel oven and roller apparatus was developed to address the difficulties inherent in making thick‐walled thermosetting composite parts: aging, moisture uptake, and low resin viscosity during lay‐up; and residual stresses, warpage, thermal degradation, and excessive void nucleation during the final cure. Unidirectional laminates were fabricated from prestaged and as‐received AS4/3501‐6 towpregs to understand the relationship between the parts' mechanical properties and the amount of prestaging (degree of cure) of the towpregs. In this manner, the feasibility of manufacturing with prestaged thermosetting towpreg was confirmed. Ultrasonic nondestructive evaluation showed that the parts manufactured from prestaged towpreg were uniform and relatively low in voids as compared to parts manufactured with as‐received towpreg. This was confirmed with scanning electron microscopy. Using three‐point bending tests, a drop in mechanical properties was found in parts manufactured from towpreg prestaged beyond 19% degree of cure. However, the parts were well consolidated and had predictable mechanical properties up to approximately 40% degree of cure. The equivalent limits on degree of cure from a companion processing study are between 15% and 22%.
Effects of preferential encapsulation of glass fiber on the properties of ternary GF/PA/PP blends
Authors: Maeng Yoo Jae , Yoon Byung Seon , Suh Moon Ho , Lee Suck Hyun , Im Wan Bin 
Published: April 2004

AbstractLong fiber molding materials are expected to play an important role in the near future. This paper describes a series of experiments performed to examine properties of ternary blends containing glass fiber (GF), polyamide (PA), and polypropylene (PP). The continuous glass fiber was impregnated with one of the blend constituent polymers by our specially designed impregnation apparatus and cut into chips of 6 mm length. These chips and the other polymer were used to produce various testing specimens in a twin screw extruder or in injection molding machine. The results indicated that the effect of fiber addition on the mechanical and rheological properties is clearly dependent on the order of impregnation process. In the blends containing the GF/PA + PP, the GFs are preferentially encapsulated with PA, and therefore the mechanical properties are superior to the blends with the GF/PP + PA in which the PP phase is located surrounding the GFs. This improved wetting of fibers by sequential impregnation not only resulted in better properties but also protected the fibers from shear action of the screw, thereby allowing significant increase in average fiber length to be achieved in the injection molding process.
Interfacial properties of regenerated cellulose fiber/polystyrene composite materials. Effect of the coupling agent's structure on the micromechanical behavior
Authors: Trejo‐O'reilly J. A. , Cavaillé J. Y. , Paillet M. , Gandini A. , Herrera‐Franco P. , Cauich J. 
Published: April 2004

AbstractThe interfacial properties of polystyrene/regenerate cellulose fiber composite materials are characterized using micromechanical tests such as the single fiber fragmentation and microbond (“microdrop test”). The cellulose fibers were grafted with different copolymers of different chemical structures as well as different molar masses ranging from 300 to 18,000 (ASA, jeffisocyanate, commercial poly)styrene‐co‐maleic anhydride and “home‐made” poly(styrene‐co‐TMI). The two polystyrene based copolymers have been shown to be miscible with polystyrene. It was found that the higher improvement of the interfacial shear strength was obtained when the fiber is grafted with the higher molecular weight, i.e., the poly(styrene‐co‐TMI).
Rheology, morphology and properties of LCP/Nylon 66 composite fibers
Authors: Wang Humin , Lee Kah Wee , Chung Tai‐Shung , Jaffe Michael 
Published: April 2004

AbstractThe rheology, morphology and properties of the composite systems of LCP, Vectra ATM 950 and Nylon 66 were investigated. The viscocity ratio of LCP and matrix has strong influence on their morphology. For LCP blends, the viscosity ratio of LCP is a critical factor in determining the blend morphology. The optical micrographs show that the good fibrillation can be achieved when the viscocity of the dispersed LCP phase is less than that of the Nylon 66 matrix at 310°C. The dispersed LCP domains tend to be spherical or cluster‐like when the viscosity ratio of the disperesed LCP phase and the Nylon 66 matrix is more than 1 at 280°C. The scanning electron microscopy (SEM) and optical micrograph observations show that Nylon 66 is immiscible with LCP, and there are two distinct phases in the blends. The morphology of LCP phase changes with the composition. LCP exhibits a fine fibril dispersed phase in the Nylon 66 matrix in the low LCP concentration. With an increase in LCP concentration, the morphology of LCP phase is changed form a fine fibril dispersed phase to a perfectly aligned continuous fiber reinforced phase in the rich LCP concentration. The tensile moduli increase with LCP concentration, especially in the rich LCP concentration. The tensile strengths increase with LCP concentration only when LCP concentration is above 40 wt%. Compared to the pure Nylon 66 fiber, the 40 wt% LCP composite sample shows a 982.1% increase in tensile modulus and a 123.3% increase in tensile strength. The mechanical properties of composite fibers are below the rule of mixtures if the LCP concentration is low, but above the rule of mixtures if the LCP concentration is high.
Mode I fracture resistance characteristics of graphite/epoxy laminated composites
Authors: Rhee K. Y. , Koh S. K. , Lee J. H. 
Published: April 2004

AbstractMode I crack resistance behavior of fiber‐reinforced (graphite/epoxy) composites laminated unidirectionally and anti‐symmetrically was studied. Double cantilever beam (DCB) specimens of stacking sequences, [O12//O12] and [(O/90)3s//(90/O)3s] were used where // represents the initial crack location. Resistance curves (R‐curves) were constructed for three initial crack lengths in order to determine the effects of initial crack length on the resistance behavior. The resistance force, GR, for a crack increment was determined from the compliance calibration method. The results show that for the case of [(O/90)3s//(90/O)3s], the initial crack deviated from the midplane and propagated in a zigzag fashion within 13th(90‐deg), while the crack propagated along the midplane for a [O12//O12] case. The results also show that for both cases, GR was affected by the initial crack length before GR was stabilized. However, GR was not affected by initial crack length when GR was stabilized for each case.
Relationship between scale effect and structure levels in fibrous structures
Authors: Pan Ning , Zhao Shumin , Hua Tao 
Published: April 2004

AbstractA series of testing samples of fibers, yarns, fabrics, and coated fabrics of the same source were prepared and then tested at constant strain rate but different gauge lengths on an Instron tester for tensile test. The results are compared to see the scale effect at different structure levels of fibrous materials. Discussions and explanations of the data are provided as well.
Effects of chemical composition and thermal stability of finishes on the compatibility between glass fiber and high melting temperature thermoplastics
Authors: Gao P. , Ward Yanling , Su K. B. , Weng L. T. 
Published: April 2004

AbstractExperimental studies were made on the surface characteristics of glass fibers with two different finishes. The effects of the chemical composition and thermal stability of the finishes on the compatibility between glass fibers and high melting temperature thermoplastics were investigated. Thermogravimetric Analysis (TGA) was used to characterize the composition of surface finishes and their thermal stability. The chemical composition of surface finishes was investigated using a combination of X‐ray photoelectron spectroscopy (XPS) and Time‐of‐Flight secondary ion mass spectrometry (ToF SIMS). Static contact angle measurements were performed at room temperature to characterize the interfacial tension between the glass fibers and thermoplastics. The study provides a fundamental understanding on some important compatibility issues between thermoplastic resins and glass fiber related to composite fabrication and application.