bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compatibilization of poly(ethylene terephthalat)/liquid crystal polymer blends by means of bisphenol a polycarboate
Authors: García M. , Eguiazábal J. I. , Nazábal J. 
Published: April 2004

AbstractA compatibilization method that consists of the addition of minor amounts of a commercial thermoplastic, which interacts or reacts with both the matrix and the dispersed liquid crystalline polymer (LCP) of thermoplastic/LCP blends, has been tested in the case of poly(ethylene terephthalate)/Vectra A950 (PET/VA) blends by means of the addition of bisphenol A polycarbonate (PC). The smaller particle size, rougher surface of the fibers and higher ductility of the PET/VA blends of a 30% of the PET substituted by PC clearly showed the suitability of PC as a compatibilizer. The moduli of elasticity of the compatibilized and uncompatibilized blends were similar. This was due to the less‐developed fibrillation of the compatibilized blends, a consequences of their smaller particle size and decreased matrix viscosity. These changes counteracted the effects of improved interfacial adhesion. The improved adhesion led to higher ductility and tensile and impact strengths in most of the compatibilized blends.
Real‐Time damage detection in thermoplastic‐based composite materials with embedded multi‐mode optical fiber sensors
Authors: Kuang K. S. C. , Cantwell W. J. 
Published: April 2004

AbstractIn this paper we describe the use of an inexpensive standard communication‐grade optical fiber for the purpose of detecting damage in glass fiber reinforced thermoplastic composite materials and hybrid fiber metal laminates based on the same composite constituent. These multi‐mode, step‐index optical fibers were embedded at different locations within the composite structure to assess their ability for structural health monitoring. In this study, the specimens were loaded under a three‐point bend test configuration, Results from the investigation have shown that these optical fibers are capable of detecting the peak failure load in the host material when embedded at locations where structural failure initiates at peak load. The output from the optical fibers was shown to be sensitive to the applied loading conditions suggesting that they can also be used to monitor structural loading. Optical micrographs of selected specimens were obtained by sectioning the specimens at the fracture location to provide confirmation of the optical fiber results.
The preparation of phenolic resin/montmorillonite nanocomposites by suspension condensation polymerization and their morphology
Authors: Wu Zenggang , Zhou Chixing , Qi Rongrong 
Published: April 2004

AbstractPhenolic resin/clay nanocomposites were prepared using a suspension condensation polymerization method that was suitable to both novolac and resole. Natural montmorillonite and two kinds of organic modified montmorillonite were adopted to investigate the effect of modification on the final morphology of the nanocomposites. X‐ray diffraction (XRD) measurements and Transmission Electron Microscope (TEM) observations showed that clay platelets were easier to be exfoliated or intercalated in novolac than in resole because novolac usually has a linear structure. The modifier with a phenyl ring was more compatible with novolac (or resole) than the aliphatic type modifier. The influence of curing on the morphology was studied as well. An exfoliation‐adsorption and in situ condensation mechanism was proposed on the formation of the nanocomposites.
Development and characterization of an all‐olefin thermoplastic sandwich composite system
Authors: Kumar Ganesan , Ramani Karthik , Xu Chongchen 
Published: April 2004

AbstractIn this investigation an all‐olefin thermoplastic sandwich system was developed and characterized. Commingled glass fiber polypropylene (PP) composite was used as skin and HDPE (PE) foam with closed cells as core. Infra‐red heating was used for melting the surfaces of the substrates for surface fusion bonding with a cold press. Two tie layer films, viz. ethylene‐propylene copolymer (EPC) and HDPE/elastomer blend, were used as hot melt adhesives for bonding the substrates. Single lap shear joints were prepared from PP composite and PE foam adherends with a bonding area of 25.4 mm × 25.4 mm to determine the interface strength. EPC tie layer provided higher bond strength (27.4 kg/cm2) to the all‐olefin sandwich system than HDPE/elastomer blend based one (19.7 kg/cm2). For EPC tie layer based sandwiches, a mixed mode a failure was observed in the failed lap shear samples; about 40% is cohesive failure through tie layer, and the rest of failure was adhesive either at PP composite or PE surfaces. Environmental scanning electron micrographs (ESEM) reveal that in the process of surface fusion bonding, PE foam cells in the vicinity of 0.80 mm interphase area were coalesced with high temperature and pressure. No macro level penetration of tie layer melt front into foam cells was observed. As the surface morphology of foam was altered on account of IR surface heating and the PP composite bonding side had a resin‐rich layer, the bonding situation was closer to that between two polymer film surface.
Polyethylene‐Palygorskite nanocomposite prepared via in situ coordinated polymerization
Authors: Rong Junfeng , Sheng Miao , Li Hangquan , Ruckenstein Eli 
Published: April 2004

AbstractA polyethylene/palygorskite nano‐composite (IPC composite) was prepared via an in‐situ coordinated polymerization method, using TiCl4 supported on palygorskite fibers as catalyst and alkyl aluminum as co‐catalyst. These composites were compared with those prepared by melt blending (MBC composites). It was found that in the IPC composites, nano‐size fibers of palygorskite were uniformly dispersed in the polyethylene matrix. In contrast, in the MBC composites, the palygorskite was dispersed as large clusters of fibers. Regarding the mechanical properties of the IPCs, the tensile modulus increased and the elongation at break decreased with increasing fiber content, while the tensile strength passed through a maximum. The tensile strength and elongation at break were much smaller for the MBC composites. The final degree of crystallinity of the IPC composites decreased with increasing palygorskite content. Regarding the kinetics of crystallization, the ratio between the degree of crystallinity at a given time and the final one was a universal function of time. It was found that large amouns of gel were present in the IPC composites and much smaller amountes in the MBC composites.
Enhancement of resin transfer molding using articulated tooling
Authors: Choi Jun H. , Dharan C. K. H. 
Published: April 2004

AbstractMold articulation is introduced in this concept for resin transfer molding (RTM) to increase mold fill times and potentially allow for the use of high viscosity, hot melt resin systems, or thermoplastics. Following a brief review of conventional RTM and a discussion of the limitations on the factors that control fluid flow through porous media, the articulated concept is described. This is followed by an explanation of the sequence of motion of an articulated segmented mold necessary for consolidation, void removal and accelerated fluid flow through a fibrous preform. An analysis of the process using a fiber preform with orthotropic permeability is outlined from which mold fill time is obtained. This is compared with conventional RTM mold fill times using typical resin properties and fiber volume fractions. For the conservative assumptions used, an improvement by a factor of ten in mold fill time is achieved using the articulated process relative to conventional RTM.
Optimizing injection gate location and cycle time for the in‐mold coating (IMC) process
Authors: Carbera‐Rios Mauricio , Zuyev Konstantin S. , Chen Xu , Castro Jose M. , Straus Elliott J. 
Published: April 2004

AbstractThe standard practice when compression molding Sheet Molding Compound (SMC) exterior automotive body panels is to in‐mold coat (IMC) the parts. Consequently, IMC needs to be considered an integral part when improving the process. Selecting the proper IMC injection gate location to obtain a defect‐free coated part and properly setting the IMC processing conditions to reduce its cycle time are both key decisions for the IMC process. In the present work, an optimization method that involves metamodeling through either linear regression or artificial neural networks is explored with two purposes: first, to select the injection gate location(s) with the objective of minimizing the potential for surface defects in the coating; and second, to set the mold wall temperature and the initiator concentration to minimize the cure time for a given minimum required flow time.
Optimal curing for thermoset matrix composites: Thermochemical and consolidation considerations
Authors: Li Min , Tucker Charles L. 
Published: April 2004

AbstractA design sensitivity method is used to find optimal autoclave temperature and pressure histories for curing of thermoset‐matrix composite laminates. The method uses a finite element simulation of the heat transfer, curing reaction, and consolidation in the laminate. Analytical sensitivities, based on the direct differentiation method, are used within the finite element simulation to find the design sensitivities, i.e., the derivatives of the objectives function and the constraints with respect to the design variables. Standard gradient‐based optimization techniques are then used to systematically improve the design, until an optimal process design is reached. In this study the objective is to minimize the total time of the cure cycle, while the constraints include a maximum temperature in the laminate (to avoid thermal degradation) and a maximum deviation of the final fiber volume fraction from its target value (to achieve proper consolidation). The simulations of curing process are performed for EPON 862/W epoxy under a conventional cure cycle, for both thin and thick parts. Time‐optimal cure cycles are found using the optimization program. Simulations of fast‐curing cycles are also examined. The optimal cycles are similar in form to conventional cure cycles, but give substantially shorter cure times. The entire scheme works automatically and efficiently, simultaneously adjusting multiple design variables at each iteration.
Numerical computation of the fiber preform permeability tensor by the homogenization method
Authors: Nedanov Pavel B. , Advani Suresh G. 
Published: April 2004

AbstractThis paper uses the homogenization method to formulate governing equations and boundary conditions to predict the permeability of anisotropic fibrous porous media. An approach is also put forth for addressing dual porosity media with this method. It is applicable to a wide range of porous materials, which may be considered with approximately periodic structure. The permeability components are calculated by solving a boundary value problem in a periodic cell. The application of the method is demonstrated on a periodic cell modeling the geometry of woven fiber performs used in composites manufacturing. The resulting equations are solved using CFD package FIDAP. The influence of dual porosity and nesting of adjacent fabric layers on the macro permeability was investigated and the results were compared with experiments.
Comparative study of the effects of different fibers on the processing and properties of ternary composites based on PP‐EPDM blends
Authors: López‐Manchado Miguel A. , Biagitti Jerico , Kenny José M. 
Published: April 2004

AbstractThe effects of the incorporation of different kinds of fibers on the physical and mechanical properties of thermoplastics elastomers based on blends of isotactic polypropylene (iPP) and ethylene‐propylene diene rubber (EPDM) are described. For this purpose, three different compositions of PP‐EPDM blends reinforced with fibers are studied and reported here. In particular, the flow behavior, mechanical properties (tensile, flexural and impact resistance) and morphology are examined. Rheological measurements confirm the viscosity increase of thermoplastics elastomers with the incorporation of the fibers. This increment is more evident in the presence of aramid fibers. In addition, the results obtained by dynamic‐mechanical analysis and mechanical properties show that the fibers act as an effective reinforcing agent of PP‐EPDM blends. In fact, a significant increase of the modulus and strength is obtained in presence of all fibers, this effect being more noticeable at higher elastomer percentages in the thermoplastic. The morphology of the ternary composites is also analyzed by scanning electron microscopy (SEM). A good interfacial adhesion between fibers and matrix is observed, but also in this case, aramid fibers are the most effective ones.
Influences of liquid elastomer additive on the behavior of short glass fiber reinforced epoxy
Authors: Arikan Aslihan , Kaynak Dr. Cevdet , Tincer Teoman 
Published: April 2004

AbstractIn this study, improvements in mechanical and thermal behavior of short glass fiber (GF) reinforced diglycidyl ether of bisphenol‐A (DGEBA) based epoxy with hydroxyl terminated polybutadiene (HTPB) modification have been studied. A silane coupling agent (SCA) with a rubber reactive group was also used to improve the interfacial adhesion between glass fibers and an epoxy matrix. 10, 20, and 30 wt% GF reinforced composite specimens were prepared with and without silane coupling agent treatment of fibers and also HTPB modification of epoxy mixture. In the ruber modified specimens, hardener and HTPB were premixed and left at room temperature for 1 hr before epoxy addition. In order to observe the effects of short glass fiber reinforcement of epoxy matrix, silane treatment of fiber surfaces, and also rubber modification of epoxy on the mechanical behavior of specimens, tension and impact tests were performed. The fracture surfaces and thermal behavior of all specimens were examined by scanning electron microscope (SEM), and dynamic mechanical analysis (DMA), respectively. It can be concluded that increasing the short GF content increased the tensile and impact strengths of the specimens. Moreover, the surface treatment of GFs with SCA and HTPB modification of epoxy improved the mechanical properties because of the strong interaction between fibers, epoxy, and rubber. SEM studies showed that use of SCA improved interfacial bonding between the glass fibers and the epoxy matrix. Moreover, it was found that HTPB domains having relatively round shapes formed in the matrix. These rubber domains led to improved strength and toughness, due mainly to the “rubber toughening” effect in the brittle epoxy matrix.
Lignin‐polypropylene composites. Part 1: Composites from unmodified lignin and polypropylene
Authors: Toriz G. , Denes F. , Young R. A. 
Published: April 2004

AbstractLignin polypropylene composites were prepared in the range of 10–60% by weight lignin content. Blending of lignin with polypropylene resulted in materials with reduced tensile and flexural strength and a dramatic decrease in unnotched Izod impact strength compared to the properties of virgin polypropylene, although moduli (Young's and flexural) were improved. Traditional surface‐treated fillers such as mica and talc performed better than lignin, but when lignin and inorganic fillers were mixed, the strength properties were improved with respect to lignin alone, perhaps because of a better lignin‐filler‐particle interaction and distribution. This could be an alternate approach for obtaining improved strength composites containing large quantities of unmodified kraft lignin. Incorporation of maleic anhydride grafted polypropylene (MAPP) as a coupling agent also improved strength properties, although at high lignin contents (e.g. 60%) there was considerable variability in the tensile strength.
A combinatorial approach for automotive friction materials: Combined effects of ingredients on friction performance
Authors: Lu Yafei 
Published: April 2004

AbstractThe combined effects of ingredient A and C in A + B + C systems where A and C are Al2O3, graphite, MoS2, steel wool and Twaron (aramid pulp), and B is a binder (benzoxazine) on friction performance were studied. Ray design with Golden Section was used for the formulated A + B + C ternary composites. Two combined factors, morphological combinations including fiber/fiber, fiber/filler and filler/filler and combinations by means of material nature including abrasive/abrasive, abrasive/lubricant and lubricant/lubricant, and their composition dependence were considered. Synergetic effects, defined as a minimum wear in wear‐composition relationships, were found in morphological combinations of fiber/filler (steel wool/Al2O3/B and Twaron/Graphite/B systems). Synergetic effects producing maximum values in friction coefficient (μ)‐composition curves were not found in all combinations. All combinations of lubricant/lubricant and abrasive/abrasive reduce μ and the effects of the combinations of abrasive/lubricant are dependent upon their abrasive or lubricant efficiency. Strong abrasive (Al2O3) plays an important role on the formation of friction layer that the transferred iron from disc to friction materials in combinations of Al2O3/lubricant/B systems, and there is no such a transfer of iron from disc to friction materials on the surface of lubricant/lubricant combinations. The S type friction transition was observed in MoS2/steel wool/B and graphite/steel wool/B systems and was caused by adhesion friction mechanism.
Thermoplastic matrix phase transitions in a carbon fiber composite, studied by contact electrical resistivity measurement of the interface between two unbonded laminae
Authors: Mei Zhen , Chung D. D. L. 
Published: April 2004

AbstractMeasurement of the contact electrical resistivity of the interface between two unbonded laminae of a continuous carbon fiber thermoplastic (nylon‐6) matrix composite during heating provides a method of thermal analysis that is sensitive to the glass transition and melting of the thermoplastic matrix. The phase transitions result in peaks in the resistivity, due to matrix molecular movement.
Scrap tire/aggregate composite: Composition and primary characterizations for pavement material
Authors: Chung Kyung‐Ho , Hong Young‐Keun 
Published: April 2004

AbstractA new type of pavement material using scrap rubber, the so‐called elastic and permeable pavement material (EPPM), was proposed in this study. EPPM is a new material to overcome water permeability and brittleness, which are defects of the conventional rubber asphalt and cement concrete, respectively. Those problems could be solved by introduction of grounded scrap rubber and structural design of EPPM. Results showed that key factors affecting the compressive strength and the water permeability of EPPM were the size of grounded scrap rubber and aggregate, the amounts and property of the binder. The optimum level of binder was about 8 wt%. The compressive strength and water permeability of EPPM were 1.1 and 116 times higher than those of conventional porous cement concrete, respectively.
Autoclave manufacturing of thick composites
Authors: Antonucci Vincenza , Giordano Michele , Imparato Sabato Inserra , Nicolais Luigi 
Published: April 2004

AbstractAutoclave manufacturing of thermoset composites is determined mainly by heat transfer phenomena. As a matter of fact, the consolidation of composite laminates takes place by the progress of the polymerization, which is activated thermally. The design and control of the autoclave process relies on the capability to manage the relationship between the temperature‐pressure cycle of the heat carrier fluid and the temperature distribution through the manufacturing part. In particular, in industrial cases, the main limitations reside in the correct evaluation of the local convective heat transfer conditions through the autoclave and in the evaluation of the local thermal inertia arising from the bagging‐tooling system. In this study, the autoclave manufacturing of thick laminates has been addressed by modeling the heat transport phenomena occurring through the composite, the bagging and the tooling system. A new methodology for the evaluation of the energy transfer regimes has been proposed accounting for the heat fluxes from the bag and the tool side, the temperature through‐the‐thickness gradients and the heat generated by the resin polymerization reaction. The proposed approach enables the prediction of the temperature history of the autoclave assembly without knowledge of the effective thermal inertia of the two external layers, which could be difficult to evaluate owing to possible deformations of the bag during the manufacturing cycle and nonuniform shape of the metallic tool along the part. Experimental data from industrial autoclave runs have been collected and analyzed to validate the method.
Influence of heat transfer and curing on the quality of pultruded composites. I: Experimental
Authors: Li Shoujie , Ding Zhongman , Xu Liqun , Lee L. James , Engelen Herbert 
Published: April 2004

AbstractBlister formation, a major concern in pultrusion, has not been studied in detail. The objective of this study is to investigate the mechanism of blister formation and the effect of process variables such as die temperature, pulling speed, die length, and composite thickness on blister formation. Dies with different length and a stop‐start method were used to investigate blister formation. The results show that for a given die and resin system, low temperature and a higher pulling speed lead to blister formation. Longer dies can prevent blister formation. Based on the experimental results, process windows for 4‐mm‐thick and 6‐mm‐thick composites are established for a vinyl ester resin. This study suggests that heater power input should be optimized in high‐speed pultrusion.
Influence of heat transfer and curing on the quality of pultruded composites. II: Modeling and simulation
Authors: Ding Zhongman , Li Shoujie , Lee L. James 
Published: April 2004

AbstractIn this study, a computer simulation code is developed to predict the dynamics of heat transfer in the pultrusion process. The die block and heater arrangement are included in the heat transfer analysis so that the simulation can provide the temperature profile at the interface between the die and the composite. The measured interface temperature profiles are then used to validate the simulation code. Energy management, i.e. heater power control along the heating die, is also considered in the simulation code. The code is capable of carrying out transient thermal analysis for both start‐up and steady‐state operation of the pultrusion process. From the experimental observations on the part quality in terms of blister formation, a processing window was obtained by showing the relation of the die length and the line speed to the part quality. The processing window is then generated numerically using the computer code based on the definition of a critical die length proposed in this work, and the result shows good agreement with the experimental data.