bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of chemical surface modification on the performance of sisal‐polyester biocomposites
Authors: Misra S. , Misra M. , Tripathy S. S. , Nayak S. K. , Mohanty A. K. 
Published: April 2004

AbstractThis article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.
Creep and recovery behavior of novel organic‐inorganic polymer hybrids
Authors: Adalja Sunil B. , Otaigbe Joshua U. 
Published: April 2004

AbstractA novel class of organic‐inorganic polymer hybrids were developed by meltblending up to 50 (v/v) % [about 83 (w/w) %] tin‐based polyphosphate glass (Pglass) and low‐density polyethylene (LDPE) in conventional plastics processing equipment. The creep and recovery behavior of these polymer hybrids at 30°C were studied to understand the effect of the Pglass on the creep resistance of the LDPE. The results suggest that the Pglass acts as a reinforcement and an increase in the Pglass loading leads to significantly lower creep strains. This creep resistance is further enhanced by pretreating the Pglass with coupling agents prior to incorporating them into the Pglass‐LDPE hybrids. The experimental creep compliance of these materials conformed excellently with empirical power‐law equation and a modified Burger's model, suggesting that the materials are linearly viscoelastic under the test conditions.
Interfacial interaction in sisal/epoxy composites and its influence on impact performance
Authors: Rong Min Zhi , Zhang Ming Qiu , Liu Yuan , Yan Hui Ming , Yang Gui Cheng , Zeng Han Min 
Published: April 2004

AbstractTo obtain comprehensive knowledge of the interfacial effect on the impact performance of sisal fiber reinforced epoxy composites, the fiber surface was modified in different ways prior to compounding. By using a surface tensiometer and dynamic mechanical analyzer, interfacial interactions in the composites were characterized. The results indicated that the chemical treatments brought about strong bonding between sisal bundles and the epoxy matrix. The subsequent impact tests revealed that the microfailure mechanism involved is a function of interfacial adhesion and fiber length continuity (i.e., continuous or discontinuous fiber). In the case of unidirectional laminates, an optimum fiber treatment should be able to result in an increased affinity between fiber bundles and matrix and a decreased intercellular adhesion. In this way, extension and uncoiling of the spirally arranged microfibrils, a main energy consumption process of plant fibers, can impart significant toughness to the composites. For short fiber composites, the interfacial strength should be properly tailored so as to increase energy dissipation through debonding and pullout of fiber bundles.
A fractal in‐plane permeability model for fabrics
Authors: Yu Boming , Lee L. James , Cao Hanqiang 
Published: April 2004

AbstractIn this paper, a fractal in‐plane permeability model for various fabrics is developed. The model is based on the fractal characteristics of pores in fiber preforms. Four different glass fabrics are considered in the modeling: plain woven, 4‐harness, bidirectional stitched, and continuous strand random mats. The fractal in‐plane permeability model can be expressed as a function of the pore area fractal dimension and architectural parameters of the fiber preform. This model also relates the permeability to porosity changes of fiber preforms under compression, which usually occurs in the molding processes. To verify the applicability of the model, the results from the present fractal model are compared with those from the one‐dimensional analysis model and with a set of permeability measurements. Good agreement is found between the two models and the permeability measurements in the general porosity ranges of interest.
Influence of processing rate and formulation on the interface strength of vinyl ester/E‐glass composites
Authors: McDonough W. G. , Dunkers J. P. , Holmes G. A. , Feresenbet E. , Kim Y. H. , Parnas R. S. 
Published: April 2004

AbstractThe single fiber fragmentation test was used to investigate the effect of gelation time on interfacial shear properties of fast reacting resin systems. We developed a processing system capable of producing single fiber fragmentation samples with gelation times that ranged from 2 min to 45 min. The interfacial properties of E‐glass fibers in vinyl ester resin were measured with single fiber fragmentation tests using a manual and an automated testing machine. We found that vinyl ester resins catalyzed with methyl ethyl ketone peroxide and promoted with cobalt naphthenate and dimethylaniline gelled in less than two minutes and had an estimated interfacial shear strength of 105 MPa. Specimens cured without the promoter gelled in 45 min and had an interfacial shear strength of 72 MPa. Further curing of the unpromoted specimens resulted in an increase in shear strength to 96 MPa. We have demonstrated the ability to make and test rapidly cured specimens, thus expanding the range of materials that can be tested using the single fiber fragmentation testing technique.
Effects on the melt rheology of systems of Nd‐Fe‐B particles suspended in a poly(phenylene sulfide) and liquid crystalline polymer blend
Authors: Guschl Peter C. , Otaigbe Joshua U. 
Published: April 2004

AbstractThe melt rheology of blends of a liquid crystalline polymer (LCP) and poly(phenylene sulfide) (PPS) and their composites with ferromagnetic Nd‐Fe‐B particles (MQP) was studied. We investigated the effects of LCP concentration, Nd‐Fe‐B particle volume fraction and size, distribution, and shear rate on the rheological properties of these composites. Enthalpy of fusion changes that were observed resulted from the addition of the LCP and Nd‐Fe‐B particles to the polymer blends/composites. The shear rate and frequency dependencies of the materials revealed a viscosity reduction at low (1–3 wt%) and moderate (10–15 wt%) LCP concentrations, and strong effects on the shear‐thinning characteristics of the melt. The suspensions of polydispersed Nd‐Fe‐B particle configurations in PPS that were of lower size ratios gave better processability, which is contradictory to previously reported behavior of suspensions containing spherical particles. Specifically, the compositions with unimodal and a bimodal distribution of Nd‐Fe‐B particles gave the lowest viscosities. The experimental data were correlated with semi‐empirical viscosity model equations of Maron‐Pierce, Krieger‐Dougherty, Eilers, and Thomas and were found to be consistent with the data. The maximum packing fraction, ϕm, of the MQP particles was estimated to be within the range of 0.78 ϕ ≤m ≤ 1.0 through graphical and parametric evaluation methods.
Structural properties and mechanical behavior of injection molded composites of polypropylene and sisal fiber
Authors: Xie X. L. , Li R. K. Y. , Tjong S. C. , Mai Y.‐W. 
Published: April 2004

AbstractComposites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L(110)α, L(040)α, L(130)α and L(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth.
In situ monitoring of residual strain development during composite cure
Authors: Crasto Allan S. , Kim Ran Y. , Russell John D. 
Published: April 2004

AbstractInternal (residual) stresses build up in a thermosetting composite as the matrix shrinks during cure, and again as the composite is cooled to ambient from its elevated processing temperature. These stresses can be significant enough to distort the dimensions and shape of a cured part as well as initiate damage in off‐axis plies, either during fabrication or under the application of relatively low mechanical loads. The magnitude of these stresses depends on a number of factors including constituent anisotropy, volume fraction and thermal expansion, ply orientation, process cycle, and matrix cure chemistry. In this study, embedded strain gauges were employed to follow, in situ, the buildup of residual strains in carbon fiber‐reinforced laminates during cure. The data were compared to those from volumetric dilatometer studies to ascertain the fraction of resin shrinkage that contributed to residual stress buildup during cure. Based on earlier studies with single‐fiber model composites, the process cycle in each case was then varied to determine if the cycles optimized to minimize residual stresses for isolated fibers in an infinite matrix were applicable to the reduction of residual stresses in conventional multifiber composites. The results of these studies are reported here.
The effect of interface characteristics on the static and dynamic mechanical properties of three‐component polymer alloys
Authors: Fisher I. , Siegmann A. , Narkis M. 
Published: April 2004

AbstractThe effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB) or fibers (GF) was investigated. The systems studied were based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semi‐crystalline highly polar copolymer. The ternary systems studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfacial properties was done using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface.Both glass fillers increased the dynamic modulus and decreased the damping of the neat polymers and of their binary blends, especially in the rubbery region. GF has a more profound effect on both the modulus and the damping. Glass surface treatments and compatibilization have only a marginal effect on the dynamic mechanical behavior of the ternary blends. Yet, compatibilization shifted the polymers' TgS to higher temperatures.Both glass fillers increased the elastic modulus of the binary blends, where GF performed better than GB as a reinforcing agent. GF slightly increased the strength of the binary blends while, GB reduced it. Both fillers reduced the ductility of the binary blends. The blends' mechanical properties were related to the morphology and their components' crystallinity. The compatibilizer increases both stiffness and strength and reduces deformability.
Monitoring the reaction progress of a high‐performance phenylethynyl‐terminated poly(etherlmide). Part II: Advancement of glass transition temperature
Authors: Bullions Todd A. , Stoykovich M. P. , McGrath J. E. , Loos A. C. 
Published: April 2004

AbstractThe cure schedule for carbon fiber‐reinforced, phenylethynyl‐terminated Ultem™ (GE Plastics) composites was studied in an attempt to optimize the resultant glass transition temperature, Tg. Reaction progress and possible matrix degradation were monitored via the Tg. On the basis of previous research, matrix degradation induced Tg reduction was expected for increases in cure time or temperature beyond approximately 70 minutes at 350°C. Using the central composite design (CCD) of experiment technique, composite panels, neat resin, and polymer powder‐coated tow (towpreg) were cured following various cure schedules to allow for the measurement of the glass transition temperatures resulting fronm cure time and temperature variations. The towpreg and neat resin specimens were cured in a differential scanning calorimeter. The glass transition temperatures of all specimens were measured via differential scanning calorimetry; the composite glass transition temperatures were also measured with dynamic mechanical thermal analysis. The composite panels and towpreg specimens showed similar trends in Tg response to cure schedule variations. Composite and towpreg glass transition temperatures increased to a plateau with increasing cure time and temperature, whereas, the neat resin showed an optimal Tg followed by Tg reduction with increasing cure time and temperature. The optimal neat resin Tg occurred within a cure time and temperature significantly below that required to maximize the composite and towpreg glass transition temperatures.
Dynamic viscoelasticity of hybrid kevlar and glass fiber reinforced LLDPE in the molten state
Authors: Hashmi S. A. R. , Kitano Takeshi , Chand Navin 
Published: April 2004

AbstractKevlar and glass fibers were used to reinforce linear low density polyethylene (LLDPE), and composite sheets of 0.8, 1.5 and 2.5 mm thicknesses were obtained by using a compression molding technique. Dynamic viscoelastic properties of non‐hybrid and hybrid composites of various compositions at 200°C are evaluated. Storage modulus (G′) and loss modulus (G″) increase with angular frequency (ω) and reinforcement. Replacement of glass fiber by Kevlar at constant loading of fibers in LLDPE increases the value of G′, G″ and η′. The fractured surface of composite shows the gradient orientation of fibers particularly in 2.5 mm thick sheet. Top and bottom layers show relatively two‐dimensional orientation as compared to the middle layer, which shows random orientation. The orientation of fibers decreases G′ and η′ of Kevlar fiber and hybrid fiber hybrid fiber reinforced LLDPE composites. The effect of change in distance between parallel plate of rheometer (change in strain amplitude) on dynamic rheological properties is studied and reported here.
The role of a third component on the conductivity behavior of ternary epoxy/Ag conductive composites
Authors: Jia W. , Tchoudakov R. , Joseph R. , Narkis M. , Siegmann A. 
Published: April 2004

AbstractConductive adhesives, based on highly filled silver particles dispersed in a liquid epoxy resin, with an aliphatic amine [diethyltriamine (DETA)] as a curing agent, were investigated. A third component was added to the epoxy/Ag system to obtain composites of better conductivity, or similar conductivity but at lower silver contents, to modify the conductive adhesive properties, and also to reduce cost. Epoxy/Ag/carbon black (CB), epoxy/Ag/carbon fibrils (CF), epoxy/Ag/SiO2 and epoxy/Ag/dispersant composites were thus studied. The effect of high curing temperature on the uniformity and resulting conductivity level was also studied. The studied systems, excluding the epoxy/Ag/CB composite, exhibited enhanced conductivities. The microstructure of most of the systems was studied by scanning electron microscopy (SEM). The micrographs produced have served to establish structure‐property relations for better understanding of the observed phenomena.
Non‐Isotropic structured fibrous media: The permeability of arrays of fiber bundles of elliptical cross section
Authors: Papathanasiou T. D. , Gravel E. M. , Barwick S. C. , Dendy E. D. 
Published: April 2004

AbstractA computational analysis of viscous flow across hexagonal arrays of fiber bundles of elliptical cross section, each consisting of up to 350 individual filaments, is carried out using the Boundary Element Method. Such arrays are non‐isotropic dualporosity systems, characterized by the aspect ratio (λ) of the fiber bundles, their inter‐ (ϕi) and intra‐tow (ϕt) porosities as well as by the number (Nf) of filaments within each bundle. The results, in terms of the hyraulic permeability (K) of these arrays, are compared to earlier analytical models and a good agreement is found. A dimensionless correlation, earlier proposed for arrays of circular cross section, is used to reduce the computed permeabilities for bundles of aspect ratio λ = 2 and λ = 3 on a single master curve. This correlation offers a simple model for the calculation of the permeability of such dual porosity systems form knowledge of ϕi, ϕt, λ and Nf. By considering bulk flow along the two principal directions of the fiber bundle, we also compare the two principal permeabilities of such arrays.
Thermokinetic effect of the aging of epoxy matrix prepregs for high performance composites
Authors: Frigione M. , Kenny J. M. 
Published: April 2004

AbstractThe reactivity and processability of prepregs for high performance composites have been investigated as a function of time and storing conditions. The study has been focused on the stability of epoxy matrix carbon fiber prepregs, affected by exposure to controlled environmental conditions before their use in composite manufacturing. Effects of the aging on glass transition temperature, reactivity and processability have been investigated by calorimetry. Dynamic, isothermal and cure simulating tests have been performed to this aim. Results on toughened TGDDMDDS epoxy matrix prepregs are reported. A theoretical kinetic model proposed for the unaged system has been adapted for aged prepregs, by properly evaluating the variations of kinetic parameters with the aging time.
Using a localized fluorescent dye to probe the glass/resin interphase
Authors: Lenhart Joseph L. , Van Zanten John H. , Dunkers Joy P. , Parnas Richard S. 
Published: April 2004

AbstractA novel technique has been developed to study the buried polymer/substrate interfacial regions by localizing a fluorescent probe on the substrate surface. Epoxy functional multi‐layers of silane coupling agents were deposited on glass and doped with small amounts of a fluorescently labeled silane‐coupling agent (FLSCA). When the dye‐doped silane layers were immersed in an epoxy/amine cured resin, a blue shift in the emission maximum was measured after resin cure. Silane layers of varying thickness were tested. Thicker layers showed smaller fluorescence shifts during cure, suggesting incomplete resin penetration into these layers. The fluorescence sensitivity to the interfacial reaction was verified with external reflection Fourier Transform Infrared Spectroscopy (FTIR) of the silane layers immersed only in the amine hardener.
Mechanical properties of glass fiber composites with an epoxy resin modified by a liquid crystalline epoxy
Authors: Punchaipetch Prakaipetch , D'Souza Nandika Anne , Brostow Witold , Smith James T. 
Published: April 2004

AbstractThe effect of liquid crystalline networks on epoxy + glass fiber composites is investigated. The matrix obtained from in‐situ curing of liquid crystalline (LC) diglycidyl ether of 4,4‐dihydroxybiphenol (DGE‐DHBP) with diglycidyl ether of bisphenol F (DGEBP‐F) by anhydride curing agent was used as the matrix for polymer composites. Impact, tensile, and flexural testing results are compared between the unmodified and modified systems. The interlaminar fracture toughness of commposites in the shear mode was determined by end notch flexure (ENF) tests. Scanning electron microscopy is used to study the fracture surfaces to understand the mechanism of fracture and interphase formation between the fiber and the matrix.
New composites based on short melamine fiber reinforced epdm rubber
Authors: Rajeev R. S. , Bhowmick Anil K. , De S. K. , Kao G. J. P. , Bandyopadhyay S. 
Published: April 2004

AbstractMelamine fibre is a new category of advanced synthetic fiber having superior heat and flame resistance with decomposition temperature above 350°C. It suitability as a reinforcing fiber for ethylene propylene diene terpolymer, abbreviated as EPDM rubber, where ‘M’ stands for polymethylene chain, was investigated. It has been observed that tensile strength and stress at 100% strain of EPDM‐melamine fiber composites increase with the addition of a three‐component dry bonding system, comprising hexamethylene tetramine (hexa), resorcinol, and hydrate silica, abbreviated HRH system. Moreover, the fiber‐filled composites anisotropy in stress‐strain properties due to preferential of the short fibers along the milling direction (longitudinal), which is substantiated by the results of swelling and fractography studies. Aging causes an increase in the modulus, tensile strength and hardness of the composites. The fractographs show an increase in interfacial adhesion between the fibers and the matrix during aging, which is further confirmed by the reduction in tan δ peak height of the aged composites during dynamic mechanical studies. Atomic Force Microscopy (AFM) studies reveal the formation of an interphase with the addition of bonding agents and a better fiber‐matrix adhesion due to aging. AFM images also confirm the role of dry bonding systems in improving the fiber‐matrix adhesion of the aged vulcanizates. The composite modulus has been theoretically calculated using the well‐known Halpin‐Tsai equation. It is found that in the transverse direction, observed modulus values are greater than the calculated values, while in the longitudinal direction, the experimental modulus values are found to be lower than the calculated values for both unaged and aged composites owing to some degree of anisotropy in fiber orientation.