bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical behavior of angle‐ply PEEK/carbon fiber laminates: Theory/experiment correlation
Authors: Cervenka A. , Sheard P. 
Published: December 2004

AbstractRegular symmetrical laminates of the {+α/−α/+α/−} sym. type were manufactured and tested using established methods. Tensile characteristics—elastic modulus and the ultimate stress/strain characteristics—were determined in the form of angular dependences on the ply‐angle α. The same mechanical properties were also simulated adopting a reported theoretical model. The correlation between the experimental and the predicted values shows an excellent agreement for the laminate stiffness. On the other hand, the fit for the ultimate properties was unsatisfactory except under conditions of linear, elastic response encountered for α→ O and 90°. Generally, a qualitative correlation has been obtained for the ultimate strength, but no relation has been established for the ultimate strain. A mechanism of fiber reorientation during loading, i.e. closing of the ply angle with the increasing strain has been found to be responsible for exceptionally non‐linear stress‐strain response in the range 30<α<60°. Coupon width and strain rate have both been found to have little effect on the ultimate properties.
Random glass mat reinforced thermoplastic composites. Part VI: Methodology for predicting the stiffness of parts
Authors: Bushko W. C. , Stokes V. K. 
Published: December 2004

AbstractRandom glass mat reinforced composites have large variations in mechanical properties, requiring a statistical characterization of their elastic properties. The broad distribution of elastic moduli is modeled by a probability density function that determines the statistical characteristics of the material property data. This characterization is used to develop a framework for predicting the stiffness of parts made of these composites. The effective elastic modulus and the structural stiffness of parts have been defined in a statistical sense, and the main properties of the effective moduli have been discussed. The effective elastic modulus, if it exists, is shown to be a system property that must be considered in conjunction with the geometry of the part and the boundary conditions.
Fiber/Matrix load transfer in cyanate resin carbon fiber systems
Authors: Armistead J. P. , Snow A. W. 
Published: December 2004

AbstractComparative single fiber fragmentation test measurements are used to charcterize cynate and epoxy resin interface load transfer with high modulus (HMS4) and high strength (AS4) carbon fibers. The HMS4 fiber forms a weak interface with a fiber controlled failure mode, and the AS4 fiber forms a strong interface with the resin properties, apparently determining the level of load transfer. The resin properties examined are critical surface energy for wetting, cure shrinkage, thermal shrinkage, and mechanical modulus and strength. The cynate and epoxy resins display no significant difference in critical surface energy. Cure shrinkage has a negligible effect on load transfer. The compressive force from thermal shrinkage is significant, but the larger Tg to testing temperature range of the cyanate resin is offset by the larger thermal expansion coefficient of the epoxy, resulting in a near equal compressive force for the two resins. There is little difference in modulus between the two resins but a significant difference in shear strength. This difference is reflected in the larger load transfer measurement for the cyanate resin. A comparison of simple one‐dimensional elastic and plastic models for the fiber fragmentation experiment resulted in better conformity with the plastic model. This would indicate that interfacial failure occurs by plastic deformation of the resin for the systems of this study.
Flow and void characterization of stitched structural composites using resin film infusion process (RFIP)
Authors: Shim Sang‐Beom , Ahn Kyujong , Seferis James C. , Berg Arvid J. , Hudson William 
Published: December 2004

AbstractThe resin film infusion process (RFIP), which is similar to resin transfer molding (RTM), was applied to investigate the possibility of manufacturing high performance stitched composites. With the objective of understanding the resin flow mechanisms and void formation in stitched fibrous perform, two recent technological developments in homogeneous tough resin and bendable stitching fibers were incorporated in producing stituched composites with RFIP. These included new lightly crosslinked thermosets (LXT) that were phenolic or amine based. Second, bendable carbon stitching reinforcement (T‐900) was utilized as a stitching fiber. Flow characteristics were inferred by ultrasonic C‐scan analysis of cured panels. Microscopic studies indicated that voids were distrubuted along the stitching fiber because of low consolidation pressure in the resin‐rich area (stitching fiber region) where the fiber volume content was lower. In contrast to stitched composites, non‐sitiched composites contained lower void content and irregular void distribution because of uniform fiber compaction. Microscopic studies of partially resin infused quasi‐istropic stitched composites demonstrated that the resin flows along the stitching fiber region and then infuses into the fibrous preform. These infusion phebnomena were the result of anistropic permeability in the preform. Consequently, anisotropic resin flow in the stitched fibrous preform was found to be related to the heterogenous textile structure caused by the stitching process.
Failure mechanisms of 2‐D and 3‐D woven fiber reinforced polymer composites
Authors: Chen H. P. , Jang B. Z. 
Published: December 2004

AbstractA simple lab‐scale weaving method was used to produce multidirectional fiber preforms to improve the delamination resistance and damage tolerance of composites. Mechanical properties measured in this study included short‐beam shear strength and damage tolerance of 2‐D and 3‐D woven composites. The constituents of fiber and matrix in these composites are Kevlar‐29 (Du Pont) and Epon 828 (Shell Chemical Co.) epoxy. Attention was directed to the differentiation of deformation and failure mechanisms in these composites as a function of material parameters and loading conditions. The sequence of failure mechanisms differ between 2‐D and 3‐D composites. Results indicated that 3‐D woven composites exhibited higher shear strength than 2‐D woven composites. Also, 3‐D composites absorbed more impact energy than 2‐D composites. Failure mechanisms of composites subjected to repeated impacts were observed intermittently by using scanning electron microscopy and light microscopy. The failure of 2‐D composites was due to a combination of shear and tensile mode, but in 3‐D composites the failure was dominated by tensile mode.
Effect of screw design on fiber damage in extrusion compounding and composite properties
Authors: Ramani Karthik , Bank Dave , Kraemer Nick 
Published: December 2004

AbstractThe mechanism of fiber length degradation during twin screw extrusion compounding and methods to reduce it through process and machine design are extremely important in discontinuous fiber reinforced composites. Fiber damage along the screw and the extruder die are determined for three screw designs with different mixing sections. The pellet quality, wet‐out, and fiber dispersion in the extruded strands are compared. The fiber orientation distributions in the screw are determined to identify regions of higher fiber interaction. The fiber damage during subsequent injection molding has also been determined. The tensile, flexural, and impact properties of the tensile bars are compared. It is found that the residence time, fill‐up, and the intesity of mixing during extrusion compounding have a predominant effect on fiber length degradation. The screw designs were seen to have a greater effect on the fiber damage in the 40 wt% glass‐filled polymer than the 30 wt% glass‐filled polymer. However, the mechanical properties of the 30 wt% glass‐filled polymer showed an increasing trend compared to the 40 wt% glass filled polymer. A screw design that provides a balance of the fiber length, wet‐out, and fiber dispersion was noted to give consistent mechanical properties.
Reaction injection pultrusion of thermoplastic and thermoset composites
Authors: Dubé M. G. , Batch G. L. , Vogel J. G. , Macosko C. W. 
Published: December 2004

AbstractCoventional pultrusion of thermoset composites is under increasing examination for emissions of harmful volatiles from the resin wetout tank. Even though the pultrusion of thermoplastic matrix composites produces no emissions, it is difficult to wet individual fibers due to their high melt viscosities. This paper addresses both the issues of volatiles and wetting with a process called Reaction Injection Pultrusion (RIP). A prototype RIP machine was used to make both thermoplastic polyurethane and thermoset polyisocyanurate matrix composites. The RIP process produces pultruded parts with low void content, good surface finish, and acceptable mechanical properties. The low viscosity constituents used in RIP help improve fiber impregnation, while the small volume of the impregnation bath reduces emissions. Processing parameters such as line speeds, catalyst levels, and die temperaures were varied to establish processing guidelines for sustained production.
Effect of grafting on phase volume fraction, composition, and mechanical behavior: Epoxy/poly (n‐butyl acrylate) simultaneous interpenetrating networks
Authors: Scarito P. R. , Sperling L. H. 
Published: December 2004

AbstractGrafted simultaneous interpenetrating polymer networks (SINs) were prepared from Epon 828 epoxy resin and n‐butyl acrylate monomer. The amount of grafting monomer (glycidyl methacrylate) was found to effect profound changes in the morphology and mechanical behavior of these materials. While the size of the dispersed rubbery phase increased from approximately 2 microns to 20 microns, the number of domains decreased, with increasing amounts of grafting agent. The total dispersed phase volume decreased with increased grafting. At the highest level of grafting, the two‐phase morphology disappeared, and only one phase was observed. With increased grafting, dynamic mechanical spectroscopy showed a movement of the loss modulus peaks toward each other, confirming an increase in compatibility in the system and showing that the compositions in each phase were becoming more alike. The SIN with the most glycidyl methacrylate (3.0 percent) showed only one peak in the loss modulus curve, supporting the single phase morphology found through microscopy. At the point of compatibility between the two networks, the SIN supermolecular structure may be visualized as becoming one complex network, where the number of grafts between the two polymer chains outnumbers the number of homopolymer crosslinks. The chemical grafts were also shown to significantly alter the free energy of mixing of the two polymers. A grafting level‐composition phase diagram showed that at well defined levels of grafting the free energy of mixing goes from a positive value to a negative value.
Statistical mechanical model of sorption and diffusion of simple penetrants in polymers
Authors: Pace R. J. , Datyner A. 
Published: December 2004

AbstractAmorphous polymers are assumed to possess a quasicrystalline structure with chain bundles that are locally parallel over distances ∼1 nm. Two possible types of random motion for a spherical penetrant in such a substrate are described, one type determining the jump frequency and activation energy of diffusion, the other type determining the jump length. The former quantities may be calculated from the model, but not the latter. Sorption of simple gases at low penetrant pressures is assumed to occur mostly in pre‐existing holes, both above and below Tg, and the same penetrant diffusion mechanism is assumed to hold in the two regions. The changes in apparent heat of solution and activation energy of diffusion observed at Tg are explained in terms of additional hole formation with increase in temperature above Tg. The theory is shown to be consistent with experimental diffusion data for several glassy and rubbery systems. Evidence is given that hole formation in simple polymers such as polyethylene may occur by chain “kinking”. For polymers possessing articulated side groups, however, it appears that hole formation arises principally from motions within these groups.
Calculator interfacing of a dynamic mechanical analyzer
Authors: Ikeda Richard M. , Starkweather Howard W. 
Published: December 2004

AbstractThe du Pont 980 dynamic mechanical analyzer has been interfaced with a Hewlett‐Packard 9825A calculator. This permits the resonant frequency and loss to be converted automatically into the engineering quantities of modulus, loss modulus, and tan δ presented in both tabular and graphical form as functions of temperature. Productivity is much greater than with previous ways of taking and processing data, and subtle features of the dynamic mechanical spectrum are more easily revealed.
Reprocessing of thermoplastics. II. Polycarbonate
Authors: Abbås Kent B. 
Published: December 2004

AbstractThe effect of recycling on the properties of injection molded polycarbonate was investigated. One unreinforced and two glass‐reinforced grades were studied. Fiber degradation was distinguished from molecular scission by spiral flow measurements and molecular weight analysis. During the first cycles the average fiber length was significantly reduced, but at later stages it approached an equilibrium. The number of scission per original polymer molecule increased linearly with the number of recycles for all systems studied, but the degradation reaction did not follow random scission kinetics. The glass reinforced grades exhibited degradation rates which were at least twice as high as that of an unreinforced polymer. This discrepancy was most probably the result of a more extensive viscous heating in the glass‐reinforced systems. The decrease in molecular weight as well as in fiber length greatly affected the impact strength of the material. The effect of processing temperature on polymer degradation during recycling was evaluated. The fraction of virgin material that has to be added to the regrind to maintain a certain property level was determined. On a 90 percent property level, an icrease in melt temperature by 1°C corresponded to an increase of 1 percent in the required amount of virgin material. Aging tests indicated that there was no significant difference in degradation rate between recycled and virgin material, although the former certainly exhibited lower absolute values of the measured property (impact strength).
Viscosity changes during isothermal and adiabatic urethane network polymerization
Authors: Richter E. B. , Macosko C. W. 
Published: December 2004

AbstractViscosity was measured as a function of time for the polymerization of a reaction injection molding (RIM) type urethane system: 4,4′‐diphenyl methane diisocyanate (MDI) with a polyester triol and dibutyl tin dilaurate catalyst. Viscosity was found to be independent of shear rate. Isothermal viscosity rise was related to extent of reaction and to Mw, by branching theory. Isothermal results at several temperatures were able to predict viscosity rise under adiabatic conditions. The gel point test commonly used to evaluate RIM systems is shown to be essentially an adiabatic test.
Rheology of short glass fiber‐reinforced thermoplastics and its application to injection molding. II. The effect of material parameters
Authors: Crowson R. J. , Folkes M. J. 
Published: December 2004

AbstractThe effect of fiber concentration, fiber length, and temperature on the shear viscosity and die swell of several short glass fiber‐filled thermoplastics has been determined. In addition, a study of the injection molding behavior of these materials has been performed. At low shear rates, viscosity increases appreciably with both fiber length and fiber concentration, but at high shear rates the effect is much less pronounced. A qualitative explanation is proposed for these effects in terms of the fiber orientation studies reported in Part I of this paper (1). The die swell is an important parameter in determining the method of mold filling of these materials, and depends strongly on fiber length.
Effects of coupling agents on the rheological properties, processability, and mechanical properties of filled polypropylene
Authors: Han C. D. , Van Den Weghe T. , Shete P. , Haw J. R. 
Published: December 2004

AbstractAn experimental study was carried out to investigate the effects of coupling agents on the rheological properties, processability, and mechanical properties of highly filed polypropylenes (PP). Inorganic fillers used were CaCO3 and glass beads, and coupling agents used were two silane coupling agents, N‐octyl triethoxy silane and γ‐aminopropyl triethoxy silane, and one titanate coupling agent, isopropyl triisostearoyl titanate. It was found that the addition of the coupling agents to the PP‐CaCO3 (50 wt percent) decreased the melt viscosity and increased the melt elasticity (first normal stress difference). However, the addition of the silane coupling agents to the PP‐glass beads (50 wt percent) affected the rheological properties of the melts quite differently. The N‐octyl triethoxy silane had relatively little effect on either the melt viscosity or the melt elasticity, whereas the γ‐aminopropyl triethoxy silane increased the melt viscosity and decreased the melt elasticity. The CaCO3‐ or glass bead‐filled polypropylenes, with and without coupling agents, were injection‐molded and the mechanical properties of the molded specimens were measured by the use of an Instron testing machine. It was found that the effect on the tensile strength and percent elongation of the filled polypropylenes depended upon the specific coupling agent utilized. A melt‐spinning study was also carried out to investigate the effect of coupling agents on the spinnability (defined as the maximum draw‐down ratio) of the PP‐CaCO3 system, and on the mechanical properties of the melt‐spun fibers. It was found that the spinnability of the PP‐CaCO3 was enhanced considerably by the addition of the coupling agents, and that the tensile strength of the melt‐spun fibers was also improved by their addition. Scanning electron micrographs were taken of the fracture surface of injection‐molded specimens and an attempt was made, with the aid of photomicrographs, to explain the mechanical properties of molded specimens observed experimentally.
Influence of viscosity and capillary force on the relationship between crack toughness and crack velocity for an acrylonitrile‐butadiene‐styrene plastic in environmental stress cracking liquids
Authors: Kambour R. P. , Yee A. F. 
Published: December 2004

AbstractThe dependence of crack propagation energy R of an acrylonitrile‐butadiene‐styrene (ABS) resin on crack velocity was characterized in air and in several organic liquids. In the liquids an abrupt transition in R from a level like that in air down to a level characteristic of the liquid occurred with decreasing crack velocity. The velocity at the transition varied strongly with liquid viscosity. A simple model of each craze at the crack tip as a set of pipes through which liquid flows, driven by capillary force and retarded by viscous drag, serves to predict the transition velocity.
Nylon‐6 containing metal halides II: Tensile properties
Authors: Siegmann A. , Baraam Z. 
Published: December 2004

AbstractFollowing the reported pronounced effects of metal halides incorporated into nylon‐6 on its glass transition temperature, melting temperature, melt viscosity, crystallization rate and final crystallinity, the tensile mechanical properties and crystallinity of nylon‐6 as affected by the absorption of metal halides were studied. At low salt content, some of the mechanical properties are substantially altered and at higher salt concentrations the ductile polymer becomes brittle. There is no marked difference between the salts studied (CuCl2, CuBr2, FeCl3) regarding their effects on the polymer mechanical properties. In the concentration range studied, absorbed Cu salts do not significantly change the polymer's degree of crystallinity, whereas absorbed FeCl3 results in a pronounced reduction, indicating its effect also on the crystalline phase.
A comparison of impact tests for assessment of fiberglass reinforced plastic toughness
Authors: Owen Gwilym E. 
Published: December 2004

AbstractAll measures of impact resistance have shortcomings. The ASTM tests, Izod, Charpy, and drop‐dart, measure impact at a single velocity. Furthermore, the Izod and Charpy tests impose an unrealistic unidimensional stress on the test specimen. Indirect gauges of impact toughness, such as the area under the tensile stress‐strain curve (tensile work), flexural modulus, or resin cracking in mandrel bend tests, are normally conducted at unrealistically low straining rates. Variable‐rate impact testers have been developed to overcome these shortcomings. In this paper, results obtained from a variable‐rate tester are compared with those from other methods for assessing composite toughness. Data are reported for flexible and brittle low profile press molding resins, tested as SMC (sheet molding compound) moldings by Izod, drop‐dart and variable‐rate impact. Indirect measures of impact resistance, mandrel bend and flexural modulus, are also discussed. The effects of resin flexibility and the composite glass content are demonstrated. The glass content affects the ultimate failure strength of the composite but not the failure of the resin matrix. The resin flexibility affects the initial stages of failure.
Polymer blends and alloys—a review of selected considerations
Authors: Barlow J. W. , Paul D. R. 
Published: December 2004

AbstractA brief overview of the important issues governing the behavior of polymer blends is presented. Thermodynamic issues which determine the phase behavior of blends are reviewed and qualitatively related to physical interactions between blend components. The influence of melt processing conditions on the resulting properties and behavior of both miscible and immiscible blends is reviewed. The physical properties of blends are reviewed and illustrated by examples from recent work on miscible blends of polycarbonate with a copolyester and on the immiscible blends of polystyrene with high density polyethylene.
Hydrolysis of poly(butylene terephthalate)
Authors: Kelleher P. G. , Wentz R. P. , Falcone D. R. 
Published: December 2004

AbstractThe hydrolytic stability of poly(butylene terephthalate) (PBT) resins and compounds was studied. Rates of reaction were determined by measuring changes in melt flow rate. Hydrolysis was slightly accelerated by contact of PBT with glass containers and reduced by incorporation of some flame retardant additives. Melt flow rates were related to tensile elongation ofunfilled PBT and tensile strength ofthe glass fiber reinforced polymer and used as failure criteria. Reaction rates were used to predict failure times at various conditions.