bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical property enhancement in short‐fiber composites through the control of fiber orientation during fabrication
Authors: Goettler Lloyd A. 
Published: May 2005

AbstractThe mechanical properties of plastics and elastomers reinforced by short fibers are generally dictated by the selection of matrix and reinforcement. However, the high tensile properties attainable in these systems through laboratory processing techniques are frequently not obtained in conventional fabrication operations. To gain a wider latitude in meeting economic and performance constraints, the control of composite structure in the fabrication step should not be overlooked. Tool geometry and processing conditions can be manipulated specifically to control the fiber orientation distribution in the product. A study of fiber orientation in composite compounds during flow through runners, gates, and dies leads to recommendations for optimizing the directional strength and stiffness according to a kinematic model. Performance data on parts fabricated from various short‐fiber composite materials bear out these projections.
Deformation design for short‐fiber‐reinforced thermoplastics
Authors: McCammond D. , North P. A. 
Published: May 2005

AbstractStiffness matrices are predicted, using the Halpin‐Tsai laminate analogy, at different locations in 4 short glass‐fiber‐reinforced thermoplastic moldings, and the resulting anisotropy and inhomogeneity discussed, relative to quasi‐isotropic values. The predictions are based on actual material structure as obtained from contact microradiographs. Considerable anisotropy and inhomogeneity are noted. The response of the materials to tensile, flexure, and shear loads is calculated and it is shown that this deviates to a lesser degree from a quasiisotropic response. Finally the load deformation behavior in plate bending and twisting are predicted using both a quasiisotropic model and the stiffness properties based on actual structure and compared with previously available experimental data. It is concluded that, in the absence of a predictive approach to fiber orientation in short‐glass‐fiber‐reinforced thermoplastic moldings, the use of quasi‐isotropic stiffness data provides an acceptable means of performing deformation design analysis. Based on the analysis of the moldings considered, the quasi‐isotropic assumption could be expected to introduce errors of less than 20 percent in deformation predictions for planar moldings.
Paper‐like filled polyethylene films
Authors: Zboril V. G. , Harbourne D. A. 
Published: May 2005

AbstractFilled high‐density‐polyethylene (HDPE) films for packaging applications have been developed. These films are of low permeability, are water and grease resistant, and can be heat‐sealed like HDPE films but have stiffness, deadfold, cuttability, and appearance similar to those of paper. The films are produced in thicknesses of 10 to 100 + μm by the standard film blowing technique. The effect of the filler type, resin parameters, and film blowing process variables on the resultant filled film properties is discussed. The commercialization of filled films and the market acceptance of the products is also briefly elaborated upon.
Recent developments in sheet molding compound technology
Authors: Newman Seymour , Fesko Donald G. 
Published: May 2005

AbstractThe molding of fiber‐reinforced thermoset components is a complex process involving a highly exothermic chemical reaction, which takes place in the presence of flow and thermal gradients. The flow in turn is complicated by time‐ and temperature‐dependent rheological characteristics. The industry has grown largely on the basis of empirical developments. However, numerous problems do remain which require increased understanding for solution. This report reviews work underway in numerous laboratories to characterize the flow and cure of sheet molding compounds and phenomena associated with these processes such as orientation, mechanical properties, residual internal stresses, mold fill, and surface defects.
Process induces fiber orientation: Numerical simulation with experimental verification
Authors: Gillespie John W. , Vanderschuren Jean A. , Pipes R. Byron 
Published: May 2005

AbstractThe performance of short fiber molded composite structures is determined uniquely by the properties of the molding material and the process induced fiber orientation. Consequently, the capability to accurately predict the fiber orientation distribution is of fundamental importance in computer‐aided mold design. Methodology for the numerical prediction of fiber orientation during the mold‐fill process is presented for a short glass fiber thermoset (57 percent phenolic resin, 10 percent calcium carbonate filler, and 33 percent glass fiber by volume). On the basis of a finite element flow characterization, Jeffery's orientation equation is numerically integrated along streamlines to calculate fiber orientation. Correlation of experimental and numerical results for an end‐gated bar with a molded‐in hole is reasonably good.
A radiant heat flux apparatus for measuring the thermal response of polymeric materials to high temperatures
Authors: Henderson J. B. , Hagen S. C. 
Published: May 2005

AbstractAn efficient and economical experimental apparatus has been designed and built which delivers a known radiant heat flux and simultaneously measures the in‐depth temperature profiles in polymeric materials. Test samples are maintained in a controlled environment and are heated radiantly by a silicon carbide heating element capable of producing heat fluxes up to 7.0 cal/cm2‐sec. The experimental data produced by this device are extremely accurate and therefore are suitable for use in verification of numerical models. The utility of the apparatus was demonstrated by measuring temperature profiles to approximately 1000°C in a glass‐filled phenol‐formaldehyde resin.
New potential silane coupling agents
Authors: Sounik David F. , Kenney Malcolm E. 
Published: May 2005

AbstractThe synthesis of two new potential silane coupling agents is described and commented on. These agents are HOSiPcOSi‐(CH3)2CH2CH2C6H4CH2I‐m and p and HOSiPcOSi(CH3)2‐CH2CH2C6H4CH2NHCH2CH2NH2‐m and p (Pc = phthalocyaninato ligand). In addition, a discussion of agents of the general class to which these two agents belong is given. In this discussion some of the special features of agents of this class are pointed out, e.g., the octahedral coordination of the silicon atoms in the agents having the potential to oxygen‐bridge to glass surfaces. Special features of the glass‐polymer linkages which these agents have the potential to form are also pointed out. Finally, the synthesis of the model isomer mixture HOSi‐PcOSi(CH3)2CH2CH2C6H4CH2N (CH2CH3)2‐m and p is described, and a very brief discussion of this model mixture is given.
Application of solid state carbon‐13 NMR spectroscopy to chemically modified surfaces
Authors: Zaper A. M. , Koenig J. L. 
Published: May 2005

AbstractThe nuclear magnetic resonance (NMR) techniques, high‐power decoupling, magic‐angle spinning, and cross polarization for high resolution in solid materials have been utilized to characterize surface‐modified silicas. Solid state Carbon‐13 NMR was used to study the chemical adsorption of a series of organosilane coupling agents on the silica surface. The type of information that can be obtained from such surface studies includes chemical bonding between the surface and the organosilane, the effects on steric hindrance of the hydrocarbon chains of the coupling agent, and other silane‐surface interactions. The approach for the analysis involved comparing the spectra of the treated silica to the spectra of the corresponding condensed coupling agents. Spectral differences in terms of changes in chemical shifts and line widths are observed. The results are interpreted in terms of chemical bonding and structural differences of the silane coupling agents adsorbed onto the surface.
The flow of suspensions
Authors: Van De Ven T. G. M. 
Published: May 2005

AbstractMost rheological and rheo‐optical properties of suspensions such as viscosity and light‐scattering intensities can be expressed in terms of the average orientation and/or the average concentration distribution of the suspended particles. In general one can distinguish several distinct regimes: (i) infinitely dilute, (ii) dilute, (iii) semi‐dilute or moderately concentrated, and (iv) concentrated suspensions. Cases (i) and (ii) are regimes in which particle interactions are either absent or only two‐body interactions are important. These cases can, in general, be well described theoretically. Regime (iii) is characterized by n‐body (n ≥ 2) interactions and is the least understood. Regime (iv) can often be described in terms of a cell model in which the motion of a reference particle, or the fluid motion around it, is described.
Dynamic mechanical properties of particulates: Application to iron‐epoxy composites
Authors: Sideridis E. , Theocaris P. S. , Kontou E. 
Published: May 2005

AbstractThe dynamic mechanical properties of composite materials, consisting of an epoxy matrix filled with iron particles, were determined over a temperature range. The storage‐ and loss moduli were evaluated in a Dynastat apparatus, with the parameters being the volume fraction of filler and the test frequency. A theoretical model was developed for comparing the experimental results with the theoretical predictions. A satisfactory correlation was obtained for the glassy region of the composite.
The influence of temperature on the impact behavior of unidirectional glass fiber‐epoxy composite
Authors: Golovoy A. , Van Oene H. 
Published: May 2005

AbstractThe influence of temperature on the impact behavior of unidirectional glass fiber‐epoxy composite was studied in the range of −20 and 150°C using a 3‐point drop weight test at a constant impact velocity of 2.2 m/s (5 mph). The impact energy per unit deformed volume was found to be very sensitive to the ratio length/thickness of the specimens. When the ratio was 4, the impacted specimens exhibited extensive delamination (shear failure) and the energy absorbed by the composite was about 14 MJ/m3between −20 and 100°C, and 18 MJ/m3at 150°C. At length/thickness above 16 the failure was mostly in tension, and the impact energy approached a constant value of about 3.5 MJ/m3, independent of temperature.
Microdielectric monitoring of prepreg cure
Authors: Zukas Walter X. , Wentworth Stanley E. 
Published: May 2005

AbstractThe feasibility of using a microdielectric sensor to characterize the cure behavior of a commercial prepreg roving was investigated. Chemical and physical characterization methods were first used to determine the uniformity of the prepreg material. Thermal, dynamic mechanical, and dielectric methods were then utilized to monitor the cure cycle. The dielectric response was found to be independent of the glass fibers of the prepreg and to show reproducible changes in the early part of cure over a temperature range of 80 to 135°C. The manufacturer's recommended cure temperature of 121°C (250°F) was found to correspond to the onset of the ultimate glass transition of the material. Variations in the dielectric response in the latter part of cure at this temperature and above were attributed in part to this event.
Nondestructive evaluation of polymers with optically generated thermal waves
Authors: Busse G. , Rief B. , Eyerer P. 
Published: May 2005

AbstractPeriodic illumination of an absorbing sample results in a surface temperature modulation which propagates into the sample as a highly attenuated and slow “thermal wave”. Thermal wave propagation depends on thermal properties and on their anisotropy. Boundaries affect both the phase and magnitude of the temperature modulation. Since thermal wave detection can be performed in a remote way, one can monitor the orientation of fibers and molecules without touching the sample. Scanned local inspection allows mapping of layer delamination caused by mechanical stress or electrical heating.
Damage tolerance in graphite‐epoxy composite: Comprehensive monitoring method
Authors: Tasnon M. , Roy C. 
Published: May 2005

AbstractA failure model is proposed to calculate the minimum expected lifetime of a graphite‐epoxy structure under cyclic loading conditions. The theoretical approach is based on the statistical theory of strength and the mechanical redistribution of stresses between piles of a damaged laminate. The use of the acoustic emission technique has permitted the development of internal damage to be monitored during cyclic loading of unidirectional laminates. The experimental results indicate that the composite can withstand greater damage at low level cyclic loading than observed during monotonic loading to failure. The theoretical modeling under development aims at predicting this behavior.
Thermoforming of ordered polypropylenes
Authors: Iaboni S. , Woodhams R. T. 
Published: May 2005

AbstractUniaxial molecular ordering of polyolefin billets by a process of roll‐drawing produces clear, transparent sheets having greatly increased strength and modulus in the draw direction whereas the strength and modulus in the transverse direction remain essentially unaltered. Such sheets may be laminated together by means of ultrasonic welding, electromagnetic induction heating or simple pressure lamination using adhesive tie layers to produce multiply laminates with controlled biaxial properties. These self‐reinforced laminates have mechanical properties which compare favorably with advanced aramid or carbon fiber composites. Conventional thermoforming techniques may be employed to convert these highly ordered sheets into shaped products having potential commercial value. In these investigations examples are presented to illustrate the methods of laminating and thermoforming of ordered polypropylene sheets. Examples are also presented to demonstrate the feasibility of pressure forming of ordered polypropylene laminates into more complex three‐dimensional shapes without loss of their mechanical properties. The techniques described in this paper may be applied to other crystalline polymers to create a new spectrum of self‐reinforced plastics capable of approaching the limits of performance.
High temperature liquid crystalline copolyester composites. Part I: A review and new data for the self‐reinforced matrix phase
Authors: Frayer Paul D. 
Published: May 2005

AbstractOur work concerns structure‐processing‐morphology‐property (SPMP) relationships in fibrous composites where the polymeric matrix may be self‐reinforced. Composites have been made using a commerically available thermotropic liquid crystalline polymer (TLCP) with nematic and isotropic transitions at 693 and 738 K, respectively. To understand the behavior of such composites one must first understand the composite nature of the matrix resin. Thus, this article covers the SPMP relationships for the self‐reinforced matrix phase alone. A review and new data are presented on the molecular dynamics of wholly aromatic copolyesters in the solid state to help clarify the nature of the temperature dependence of mechanical properties. Subsequent papers concern short (Part II) and continuous (Part III) fiber reinforced composites.
Electrical properties of exfoliated‐graphite filled polyester based composites
Authors: Foy John V. , Lindt J. Thomas 
Published: May 2005

AbstractWork has been done to develop and optimize a procedure for the preparation of electrically conductive exfoliated‐graphite filled unsaturated polyester composites. The exfoliated graphite flakes impart excellent electrical properties to the polyester composite. EMI (electromagnetic interference) shielding effectiveness, comparable to that of exfoliated graphite alone, has been observed over a frequency range of 0 to 1000 MHz with composite samples containing as little as 4 weight percent of exfoliated graphite. The resistivities approached the value for exfoliated graphite in the c‐direction (0.03 μ‐cm) at a graphite loading of 11 weight percent. It has been observed that the mechanical integrity of the composite remained good up to graphite loadings of some 17 weight percent. The polyester readily wets the graphite and penetrates most of the graphite open pore volume during processing. Flow visualization measurements have been made in a transparent compression molding apparatus. No effect of the flow conditions on the apparent electrical properties has been found.
High intensity compounding of mica‐filled thermoplastics
Authors: Cacoutis Spyridon , Woodhams Raymond T. , Van De Poll Peta Gay Kleyn 
Published: May 2005

AbstractHigh‐speed turbine mixers have been adapted for compounding filled thermoplastics by the partial flux method. The extreme shearing forces exerted by the mixing impellors simultaneously mixes and delaminates mica fillers to form finely dispersed compounds in a granular, partially fused state which can be directly injection molded without pelletizing. In practice, one turbine mixing unit can be employed for compounding all types of resins and fillers. The partial flux method permits compounding to be accomplished at peak sensor temperatures that are considerably below the resin softening or melting transitions, frequently 50°C less than normal compounding temperatures. The short residence times and reduced energy requirements possible with partial fluxing results in substantial cost reduction without compromising quality or performance. Examples are provided for polypropylene, nylon 66, poly(butene terephthalate), poly(ethylene terephthalate) and poly(phenylene oxide) alloys. Impact modifiers derived from carboxylated polyolefin waxes may be dispersed by the intense shearing action to form highly subdivided submicron particles, which promote crazing and shear deformation during fracture testing, thereby contributing to increased composited toughness with minor sacrifice in modulus and strength. The mechanical properties of micafilled thermoplastics have also been compared with those of short glass fiber composites. In certain applications requiring stiffness and dimensional stability at elevated temperatures, mica composites prepared by intensive mixing in a turbine mixer may be economically substituted for glass fiber counterparts.
A study of low‐energy impact of continuous carbon‐fiber‐reinforced composites
Authors: Moore D. R. , Prediger R. S. 
Published: May 2005

AbstractLow‐energy instrumented falling weight impact tests were used to study the failure mechanisms in various multiangle laminates of continuous carbon‐fiber‐reinforced composites. C‐scans of impacted specimens were conducted to monitor an area for delamination damage. Photography of the tension surface during impact enabled the onset of tension surface cracking to be detected. These techniques were employed for composites based on thermoplastic, poly(ether ether ketone) (PEEK), and thermoset (epoxy system 934) matrix materials. In addition, a range of ply numbers (8 to 40) were used in preparation of the multiangle laminates. Tension surface splitting can be shown to be the first failure mechanism during impact. Initiation of a tension crack occurs at a lower absorbed impact energy than that for the onset of delamination damage.
Monitoring progression of mode II delamination during fatigue loading through acoustic emission in laminated glass fiber composite
Authors: Roy C. , El Ghorba M. 
Published: May 2005

AbstractAcoustic emission (AE) was used to monitor damage development in a glass fiber/epoxy composite during monotonic and cyclic Mode II loadings of DCB specimens. AE parameters such as event count rates and accumulative event counts together with the distribution of events by time and location in the DCB specimen were used as proper indicators of the damage growth at various stages during testing. AE proved to be a powerful technique to predict in real time the interlaminar failure stress (delamination in Mode II) in both the static and the dynamic tests. An S‐N curve constructed entirely on the AE signatures recorded during fatigue testing exhibits three distinct stages enabling delineation of period of damage initiation, the period of damage growth, and finally the occurrence of delamination. A generalized expression based on the nonlinear cumulative damage model was developed to correlate AE activity with the damage development in the composite during cyclic loading. The fatigue data to date agree well with this method of prediction of the fatigue life.
Role of morphology and coupling agent in fracture performance of glass‐filled polypropylene
Authors: Denault J. , Vu‐Khanh T. 
Published: May 2005

AbstractThe effect of silane coupling agent on the morphology and fracture performance of particulates‐filled polypropylene was investigated. The onset of the crystallization at the filler‐matrix interface was observed by optical microscopy. This analysis shows that the silane alters the matrix morphology by inducing nucleation at the filler‐matrix interface. This effect was attributed to the physisorbed layer of silane on the filler. The fracture performance of the composites was analyzed by the post yield fracture mechanics approach. The effect of coupling agent on the fracture performance was found to occur at a very low concentration, whereas subsequent increase in silane concentration had no effect. Furthermore, the effect of coupling agent depended on concentration of filler. Silane treatment had a detrimental effect at low concentration of filler. However, at high concentration of filler, an improvement in the filler‐matrix adhesion had a beneficial effect on the fracture performance. Two phenomena, the morphological effect and the competition between the contribution of the matrix‐filler interface and the contribution of the matrix, were found to be possible explanations for the variation of KRmax with filler concentration and adhesion at the matrix‐filler interface.
Effects of cellulose fibers in polypropylene composites
Authors: Bataille P. , Ricard L. , Sapieha S. 
Published: May 2005

AbstractA systematic study of the effect of surface pretreatment of cellulosic fibers and the processing time and temperature on the mechanical properties of the cellulose‐containing polypropylene was undertaken. Using non‐treated fibers, the elastic modulus increased gradually with the cellulose content, typically doubling its value at 30 phr fiber content. Treatment of fibers with coupling agent improves significantly the interfacial adhesion and therefore the mechanical properties of composite. Scanning electron micrographs reveal that the shear stress is sufficiently high to break and delaminate the cellulosic fibers. Addition of maleic anhydride modified polypropylene also improves the properties of resulting composites.
Micromechanical characterization of composite materials based on poly(styryl pyridine) thermoset resin
Authors: Caux X. , Coulon G. , Escaig B. 
Published: May 2005

AbstractThe purpose of this paper is to propose a micromechanical characterization of composite materials through measurement of the work‐hardening rate K in the preyield stage during compression tests at constant strain‐rate. This method belongs to a more general framework where the non‐elastic deformation of glassy polymers is analyzed from a metallurgical point of view. The parameter K varies as the inverse of the nucleation rate of dislocations which are responsible for the non‐elastic deformation. The method is used, here, to characterize a model composite material : PSP resin (poly(styryl pyridine)) filled with glass beads. K measurements show that introducing glass beads in the PSP resin enhances its ability to deform plastically, i.e. the presence of glass beads increases strongly the nucleation rate of dislocations. K‐measurements and scanning electron microscopy investigations seem to show that the coupling agent A1100 is not appropriate to the PSP matrix.