bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoanalytical investigation of composite lamination
Authors: Gotro J. , Appelt B. , Yandrasits M. , Ellis T. 
Published: May 2005

AbstractGlass cloth reinforced epoxy resins are commonly used to make composites. The performance of these laminates depends strongly on optimizing cure kinetics and rheology for a given chemical composition and temperature/pressure profile. Aborted flow tests (weight percent resin squeezed out during a given temperature/pressure cycle) is frequently used to emulate lamination processes and/or to evaluate new formulations. The cure reaction was monitored using differential scanning calorimetry, rheology, and dielectrometry. These techniques show that the cure kinetics are controlled by the temperature profile. The viscosity and the macroscopic flow, however, are affected by the temperature profile, i.e. decrease in viscosity with rising temperature, as well as the cross‐linking kinetics which lead to an increase in viscosity. Gravimetric and thickness measurement indicated a non‐uniform resin distribution across the laminate, with a lower resin content found at the edges. Macroscopic flow is controlled by three dimensional heat transfer, which leads to a dynamic temperature distribution and, concomitantly, to a cure/rheology profile. This was demonstrated graphically by marking layers of reinforced resin and monitoring the movement of the markers.
Viscoelastic response of unidirectionally reinforced thermoplastic composites to off axis deformation
Authors: Tomkinson Gayle D. , Vallance Michael A. 
Published: May 2005

AbstractMeasurements of dynamic viscoelastic in‐plane shear modulus have been made for unidirectional carbon fiber composites with amorphous engineering thermoplastics as the binder resins. The viscoelastic response is modeled by a three‐phase, finite‐element model in which fiber placement in the plane perpendicular to the fiber axes is largely disordered. In the model, fibers tend to chain with the distance of closest approach dictated by several factors, including the tendency for the resin to wet the entire fiber surface. Polished section microscopy supports the assumed microstructure. The model includes an adsorbed primer layer at the fiber interface with perturbed viscoelastic response. The model is useful throughout the temperature range up to and including the glass transition of the binder resin.
Effects of ambient aging of 5245C/graphite prepreg on composition and mechanical properties of fabricated composites
Authors: Scola Daniel A. , Vontell John , Felsen Marvin 
Published: May 2005

AbstractA bismaleimide modified epoxy 5245C/graphite prepreg was subjected to ambient conditions for periods up to 140 days. The effect of this ambient aging on the prepreg composition and mechanical properties of composites fabricated from aged prepreg was investigated. The results show that small but definite composition changes occur as a result of ambient aging. These compositional changes are also reflected in small decreases in shear and flexural properties at room and elevated temperatures, dry and wet.
Slow crack propagation in a heavily‐filled particle reinforced epoxide resin
Authors: Montes‐g G. M. , Draughn R. A. , Simpson T. H. 
Published: May 2005

AbstractThe fracture properties of two proprietary composite dental restorative materials and a model composite system were studied to determine the effects of filler concentration, exposure to water, and particle/polymer adhesion on subcritical crack propagation. Particle content ranged from 36 to 60 volume percent. The double torsion (DT) test was used to measure relationships between the stress intensity factor (K1) and the speed of decelerating cracks or the rate of loading in dry and wet materials in air at laboratory conditions. Materials with weak particle/polymer interfaces fractured by continuous crack growth in both dry and wet conditions. In dry and wet materials with strong interfaces, continuous cracking also occurred at the low end of the range of speeds observed (10−7 to 10−3 m/s), but under test conditions of high crack speeds unstable (stick‐slip) crack propagation was found in dry specimens and in wet model composites with 41 percent vol, filler. Water had a corrosive effect lowering K1c for continuous crack propagation. The exponential dependence of K1c on crack velocity, representing the viscoelastic response of the materials, was positively correlated to the filler concentration and the plasticizing effect of water. Observations on fracture surfaces indicate that low velocity cracks (<10−5 m/s) propagate through regions of high stress concentrations (interfaces, corners, pores) while at higher crack velocities failure occurs by a combination of interparticle and transparticle fracture.
The effect of the interface/interphase on fiber composite properties
Authors: Piggott M. R. 
Published: May 2005

AbstractThe interfacial region between fibers and matrix in fiber composites governs the transfer of forces between the relatively weak and compliant matrix and the reinforcing fibers. An effective interphase can ensure that the mechanical properties of the composite reflect the high strength and modulus of the fibers. Although composites can be made with the expected strengths and moduli, it is not entirely clear why this is achieved: Tests with critical composites, i.e., those containing very short aligned fibers, do not show the expected stress‐strain behavior. This paper examines the effect of an interphase having a shear modulus that is less than that of the matrix. It is found that to explain the Young's moduli of the short fiber composites, the interphase must have a very low modulus indeed; i.e., a few kPa at most. In addition, the strength results can be accounted for only if we assume that the short lengths of fiber used in the experiments had higher strengths than anticipated. Although agreement between experiments and theory is thus not very good, the small amount of experimental evidence available indicates a need for further systematic experiments on critical (i.e. short aligned fiber) composites before firm conclusions are drawn.
Dynamic mechanical analysis studies of the interphase
Authors: Chua Ping Seng 
Published: May 2005

AbstractThe dynamic mechanical properties of unidirectional glass‐fiber‐reinforced polyester measured along the fiber direction were recently investigated. In the same polyester, the type of organosilane coated on the glass fiber, the amount of organosilane, the fiber volume fraction, and the fiber diameter affect the value of the loss tangent, tan δ, at the glass‐transition temperature of the glass‐fiber‐reinforced polyester. The interfacial shear strength and the tan δ at the glass‐transition temperature of the glass‐fiber‐reinforced polyester show good correlation suggesting that the latter can be used to characterize the quality of the interphase. Factors affecting the glass‐transition temperature and the application of Zorowski and Murayama's equation in the characterization of the interfacial adhesion are also discussed.
Parameters determining the strength and toughness of particulate‐filled epoxy resins
Authors: Roulin‐Moloney A. C. , Cantwell W. J. , Kausch H. H. 
Published: May 2005

AbstractThe effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin‐filler adhesion, and toughness of the matrix on the stiffness, strength, and toughness of particulate‐filled epoxy resins were evaluated. The mechanisms of crack initiation and subsequent crack propagation in these multiphase materials are discussed and illustrated by scanning electron microscopy of fracture surfaces.
Optothermal analysis of polymer composites
Authors: Krapez J. C. , Cielo P. , Maldague X. , Utracki L. A. 
Published: May 2005

AbstractA number of thermographic techniques under optical‐radiation heating are described for the nondestructive evaluation of different kinds of fiber‐filled polymer‐based composites. Shallow delaminations within carbon‐fiber reinforced laminates can be detected by this method under wide‐area surface heating to 5 or 10° above ambient. A number of image‐processing algorithms are described for improving the visibility of subsurface defects. Spot‐heating techniques are presented for the characterization of fiber concentration, distribution, and orientation in carbon or steel fiber‐filled composites. Particular emphasis is given to the possibility of mapping fiber‐orientation properties at gradually deeper layers below the surface. These optothermal techniques appear to be a convenient tool for the inspection of opaque composites in terms of rapidity, lack of sample preparation requirement, and simplicity both in its implementation and in the interpretation of results.
Characterizing high performance composite processability with dynamic fiber wettability measurements
Authors: Lee Walter J. , Seferis James C. , Berg John C. 
Published: May 2005

AbstractDynamic fiber wettability measurements are performed on T‐300 carbon and Teflon fibers immersed in hexa methyl disiloxane (HMDS) silicone oil and a difunctional liquid epoxy resin, neopentyl diglycidyl ether (NPDGE). Specifically, four types of these carbon fibers, which are used to reinforce high performance composites, are studied. Decreases in the wetting force are observed for progressive immersions of all carbon fibers in the silicone oil but not observed with Teflon fibers, indicating adsorption may be occurring on the carbon surface. Perimeters determined from these wetting measurements on carbon fibers are larger than those calculated, assuming the fibers to be smooth cylinders. Scanning electron micrographs suggest this difference is attributable to surface crenulations. All carbon fibers immersed in the epoxy resin show non‐zero contact angles.
The influence of the interphase on composite properties: Poly(ethylene‐co‐acrylic acid) and poly(methyl vinyl ether‐co‐maleic anhydride) electrodeposited on graphite fibers
Authors: Crasto A. S. , Own S. H. , Subramanian R. V. 
Published: May 2005

AbstractThe electrodeposition of saturated copolymers onto carbon fibers is investigated, focusing particular attention on improvement of shear and impact properties of the corresponding composites. Carbon fibers are electrocoated with poly(ethylene‐co‐acrylic acid) and poly(methyl vinyl ether‐co‐maleic anhydride) from aqueous media, and fabricated into epoxy composites. The results of interlaminar shear strength (ILSS) tests, initially employed to assess fibermatrix adhesion, are vitiated by the occurrence of mixed‐mode failure. Interfacial shear strength (IFSS) is hence evaluated by stressing single‐fiber composite specimens to obtain ultimate aspect ratios of the fiber fragments. The data are combined with fiber strengths by a recently developed statistical theory (1) to yield a distribution for IFSS. Both copolymer interphases improve fiber‐matrix bonding to an extent greater even than that obtained with commercial fiber surface treatment. Good fiber‐matrix adhesion is further apparent from SEM studies of fractured ILSS test specimens. A key to this improved adhesion is the interpenetration of matrix resin and interphase polymer, revealed by electron microprobe analysis (2). Notched Izod impact strength is also increased over uncoated‐fiber composites. These copolymer interphases behave as deformable interlayers, absorbing impact energy and blunting the growing crack tip. Further energy is absorbed in deflecting the crack through a more tortuous path. Simultaneous improvements in impact and shear strengths are thus obtained, which may be further enhanced by optimizing the electrodeposition parameters and the coating thickness. The influence of the interphase on composite properties is better understood from this study, paving the way for refinement in interphase design.
Review of manufacturing of fiber composite components by filament winding
Authors: Munro M. 
Published: May 2005

AbstractA summary of the simple to very complex fiber composite components that have been fabricated by automated filament winding is presented. The process of filament winding, where resin‐impregnated, high strength, high modulus fibers are placed on a rotating mandrel (under controlled tension) in a specified geometric pattern, is then described in detail. A qualitative comparison of the filament winding of fiber composite components by conventional and robotic winding systems is presented next. The results indicate that a robotic winding system can be a viable alternative to conventional filament winding for certain applications. Finally, the concepts of lightweight winding systems, hybrid filament winding processes, and advanced filament winding techniques are presented.
Short fiber reinforced thermoplastics. I. Rheological properties of glass fiber reinforced Noryl
Authors: Vaxman A. , Narkis M. , Siegmann A. , Kenig S. 
Published: May 2005

AbstractAn experimental study on the flow behavior of glass fiber reinforced Noryl (a commercial poly(phenyleneoxide)/polystyrene blend) using a capillary rheometer is described. The effect of fiber concentration on shear viscosity and die swell was studied at various temperatures. Breakage of glass fibers during flow through the rheometer is discussed; it was found that the average fiber length (about 230 μm) was not significiantly altered, except at the highest shear rate (575 s−1) studied. The incorporation of short fibers into thermoplastic polymer melts increases their viscosity without changing the basic rheological character‐shear rate dependency. No discernible viscosity changes were measured by incorporating 10 weight percent fibers, and upon further increase of fiber concentration from 20 to 30 weight percent no appreciable increase in viscosity was noted. It is shown that short glass fibers cause a large reduction in extrudate swell. The presence of voids and fiber orientation contribute to the decrease of the die swell, an effect greater than expected from volumetric considerations alone.
Void formation in short‐fiber thermoplastic composites
Authors: Vaxman A. , Narkis M. , Siegmann A. , Kenig S. 
Published: May 2005

AbstractVoids, or bubbles, are formed in short‐fiber thermoplastic composites because of entrapment of air in the compounding and melt flow processing steps and as a result of uneven shrinkage due to temperature gradients involved in the solidification step by cooling. The experimental results suggest that bubble nucleation takes place at fiber ends and their volume content depends on processing conditions. The shape and distribution of the voids were studied by optical examination of longitudinal sections of extrudates, using standard metallographic polishing technique and reflected light microscopy. The void volume fraction of extrudates was found to increase with increasing extrusion rate, temperature, fiber concentration, and fiber length, and with a decreasing draw ratio. The void content in fiber‐glass‐reinforced injection moldings is low, ≈︁1% by volume; however, by heating these moldings, the contained pressurized bubbles expand and significant void volume fractions are observed.
A method of forming composite structures using in situ‐formed liquid crystal polymer fibers in a thermoplastic matrix
Authors: Bassett B. R. , Yee A. F. 
Published: May 2005

AbstractA new high speed and potentially economical method of creating a composite material and structures therefrom is tested. The method consists of spinning composite fibers from a melt blend of a thermoplastic with a liquid crystal polymer (LCP). Discontinuous fibrils of the LCP are formed in situ during the spinning process. These composite fibers are aligned and placed in a mold and heated to melt the thermoplastic matrix, but not the fibrils. A finished composite structure reinforced by the LCP fibrils is obtained when the thermoplastic phase is consequently consolidated. Our experiments show the proposed process is reasonable for an easily processed polystyrene matrix. High modulus fibrils with essentially infinite L/D ratios are readily produced in the extrusion process using 40 wt% of a wholly aromatic poly(ester‐co‐amide) LCP from Celanese. The integrity and alignment of the LCP fibrils is retained in the molding step. Mechanical tests show that the fibers produced by high shear rate processing have a stiffness approaching 23 GPa and match an axial rule‐of‐mixtures theory. The use of polystyrene resulted in brittleness. Molded composite plates exhibit slightly lower stiffness and significantly lower strength than individual fibers.
Modeling fracture of resin matrix composites
Authors: Herakovich Carl T. 
Published: May 2005

AbstractCharacteristics of the fracture of resin matrix fibrous composites are discussed with emphasis on the physical parameters influencing fracture and the requirements of a suitable model for predicting crack growth. The influences of notch geometry, fiber orientation, specimen geometry, and far field loading on crack growth in unidirectional resin matrix composites are discussed. The normal stress ratio theory is reviewed and its applicability for crack initiation in unidirectional resin matrix composites is considered. Experimental results from a variety of tests on resin matrix composites are reviewed and compared with theoretical predictions. It is shown that the normal stress ratio theory correctly predicts the initiation site and direction of crack growth from an existing notch. Predictions of critical stress are less consistent being quite accurate in some cases, but less accurate in others.
Random glass mat reinforced thermoplastic composites. Part IV: Characterization of the tensile strength
Authors: Stokes Vijay K. 
Published: May 2005

AbstractRandom glass mat thermoplastic composites, which can be thermostamped to form complex deep‐drawn parts with ribs and bosses, are excellent materials for making low‐cost stiff parts with relatively high impact strength. However, the mechanical properties of these materials, as determined by standard tensile tests, are known to exhibit large scatter. And the tensile modulus in these materials can vary by a factor of two over a 12.7‐mm distance. In an earlier effort, measurements of the local tensile moduli of long, thin, 12.7‐mm‐wide strips along both thin edges (left and right) of the specimen and across the face were used to show that the local tensile modulus is well approximated by the arithmetic mean of the local left‐ and right‐edge tensile moduli. To establish the tensile strength of these materials, the local tensile moduli of long dog‐bone specimens are first characterized along the length, after which the specimens are pulled to failure. The tensile strength is shown to correlate well with the arithmetic mean of the local left‐ and right‐edge tensile moduli.
Analysis of resin injection molding in molds with preplaced fiber mats. I: Permeability and compressibility measurements
Authors: Trevino L. , Rupel K. , Young W. B. , Liou Ming J. , Lee L. James 
Published: May 2005

AbstractThis work presents the characterization of fibrous reinforcement mats in resin injection molding. The fiber mat characterization involved determining the mat permeability and compressibility. Mold filling experiments were conducted using two or more different fiber types in the mat stack, which created transverse porosity, permeability, and compressibility variations. The effect of these variations was studied by taking flow pressure measurements and observing the progress of the flow front of a non‐reactive fluid filling a clear acrylic mold that contained the reinforcement mat stack.
Effect of physical aging on the toughness of carbon fiber‐reinforced poly(ether ether ketone) and poly(phenylene sulfide) composites. I
Authors: Ma Chen‐Chi M. , Lee Chang‐Lun , Chang Min‐Jong , Tai Nyan‐Hwa 
Published: May 2005

AbstractThe effect of physical aging on the penetration impact toughness and Mode I interlaminar fracture toughness of continuous carbon fiber (C.F.) reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites has been investigated by using an instrumented falling weight impact (IFWI) technique and a double cantilever beam (DCB) test. Composite materials studied are aged below their glass transition temperature (Tg) at various periods. Initiation force and energy of damage, failure propagation energy, impact energy and ductility index (D.I.) are reported. The Mode I critical value of strain energy release rate (GIC) of the unidirectional carbon fiber‐reinforced PEEK (APC‐2) composites is obtained. Results show that aging has a significant effect on the toughness of both composite materials. Energy absorbed during impact decreases with the increase of aging temperature and period. The PEEK/C.F. composites exhibit a higher retention of impact toughness than that of the PPS/C.F. composites after aging; however, the PPS/C.F. composites show a much higher ductility index. The Mode I fracture mechanism of the APC‐2 composite is a combination of stable and unstable failure and shows a “stick‐slip” behavior. Owing to the formation of a relative rigid structure, the fracture toughness (GIC) of APC‐2 decreased with the increase of aging temperature and period.
Hygrothermal behavior of carbon fiber‐reinforced poly(ether ether ketone) and poly(phenylene sulfide) composites. I
Authors: Ma Chen‐Chi M. , Lee Chang‐Lun , Chang Min‐Jong , Tai Nyan‐Hwa 
Published: May 2005

AbstractThe hygrothermal behavior of carbon fiber‐reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites subjected to moisture and temperature is investigated in this study. The properties of both composites exposed to temperature/humidity and immersed in water for extended periods are studied. Properties studied include moisture sorption, crystallinity, dynamic mechanical response, tensile strength, and flexural strength. Both the PEEK/C.F. and the PPS/C.F. composites exhibit good moisture/temperature resistance and property retention after hygrothermal exposure. The diffusivities and the equilibrium moisture absorption are measured at 60, 70, 80°C with 85% R.H. (relative humidity). A Fickian type diffusion is observed at all exposures. Crystallinity increase of the composites is found for the PPS/C.F. composites exposed to 80°C with 85% R.H. environment and is correlated with the damping properties in the dynamic mechanical study. However, the hygrothermal effect on the crystallinity and the glass transition temperature of the PEEK/C.F. composites is negligible. Mechanical properties of the PEEK/C.F. composites decrease slightly with the increase of temperature/moisture and exposure period. Mechanical property reductions of the PPS/C.F. composites decrease with the increase in exposure temperature when subjected to a similar environment; this is due to the relatively complete molecular relaxation and additional crystallization at higher temperatures.