bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of fuming nitric acid surface treatment of ultra‐high modulus polyethylene fibers on the mechanical properties of their composites
Authors: Taboudoucht A. , Opalko R. , Ishida H. 
Published: December 2004

AbstractThe effect of hot fuming nitric acid (FNA) treatment on the adhesion of ultra‐high modulus polyethylene fabrics to an epoxy resin has been investigated. Mechanical and molecular characterization of the interface has been attempted. Fourier transform infrared diffuse transmittance spectroscopy has been used to monitor the chemical changes introduced by the FNA treatment as well as the nature of the interface between the fibers and the epoxy resin on the molecular level. Scanning electron microscopy has been used to examine the morphological consequences of the FNA treatment. Flexural and interlaminar shear properties of the composites have been measured as a function of the extent of surface treatment. Esterification of the FNA treated polyethylene fibers is used to examine the role of surface functionality to the mechanical performance.
Material response of a semicrystalline thermoplastic polymer and composite in relation to process cooling history
Authors: Lawrence Wesley E. , Seferis James C. , Gillespie John W. 
Published: December 2004

AbstractA model capable of predicting the process‐induced macroscopic in‐plane material response of semicrystalline thermoplastic matrices and their composites was developed. Thi sinvestigation focused on the material response of a single layer or ply of neat PEEK matrix and its carbon fiber composite (APC‐2) when subjected to various processing histories. Specifically, the response of the material moduli and processing strains as a function of temperature and the degree of crystallinity were studied. The kinetic‐viscoelastic response of the matrix was determined from a modified form of the Standard Linear Solid model. A constitutive relation was proposed to quantify resign shrinkage as a function of thermal history, which incorporated crystallization. For a specific process history, the effective composite mechanical properties were determined from micromechanics models. Both neat and composite processing strains were evaluated to show the effect of fibers on the matrix dominated response (90° direction). In addition, comparisons of model moduli predictions with experimental measurements were performed. This study demonstrated that an increase in the degree of crystallinity results in an asymmetric shift of the modulus in the glass transition region to higher temperatures. Also, strains due to crystallization were predicted to be much smaller in comparison to the strains resulting from thermal contraction of the PEEK matrix.
Compression molding simulation of chopped fiber reinforced polymeric composites in plate‐rib type geometry
Authors: Kim Junil , Shiau Y. C. , Lee L. James , Im Y. T. 
Published: December 2004

AbstractA study on anisotropic material flow of polymeric composites in compression molding was conducted. Flow resistance and material anisotropy were measured by compression and tension tests to quantify the inhomogeneity of chopped fiber reinforced polymeric composites. The material was assumed to obey Hill's anisotropic yield criterion with its associated flow rule. An anisotropic finite element formulation was developed to simulate the material flow under various conditions. This two‐dimensional model was applied to plane strain compression in a mold with plate‐rib type geometry to substantiate the effect of fiber induced anisotropy. The predictions were compared with experimental results.
Mechanical and rheological properties of reinforced polyethylene
Authors: Malik T. M. , Farooqi M. I. , Vachet C. 
Published: December 2004

AbstractThe rheological and mechanical properties of a high density polyethylene (HDPE) filled with surface‐treated mica flakes are reported. Young's modulus decreases with different treatments, whereas break elongation and maximum strength slightly increase. Young's modulus increases with the addi ion of mica flakes, but the decrease in elongation is also quite significant. For 20% mica composites, hardly any change was observed in the properties. The high shear viscosity does not show any significant effect as a result of the surface treatment. Viscosity of composites increases with silane treatment and decreases with titanate treatment. It is suggested that the coupling agent, depending on its chemical structure and nature of the filler, may act as an adhesion promoter or as a lubricating agent.
Analytical model for prediction of the damping loss factor of composite materials
Authors: Crane Roger M. , Gillespie John W. 
Published: December 2004

AbstractNumerous approaches have been undertaken to determine the damping of composites. These approaches can be grouped into micromechanical, macromechanical, and structural approaches. This paper describes a macromechanical approach that has been experimentally validated using various S‐2 glass/3501‐6 laminates. Our approach is an extension of the elastic‐viscoelastic approach, which accounts for the frequency dependence of the loss factor. The experimentally determined material loss factor for the glass/epoxy determined in a previous investigation is used as input to the model. The material complex moduli are then determined and used as input to the model. The loss factor of a quasi‐isotropic configuration is analytically determined in the frequency range of the experimental data. The loss factors for these beams are then experimentally determined using a cantilever beam configuration set into vibration with an impulse excitation. The loss factor at various frequencies are determined using the half power band width technique. The analytical values are within 15% of the experimental values in the frequency range of test. In addition, a parametric study is given on the effect of fiber orientation on loss factor. The analytically determined loss factor using the proposed model shows that inconsistencies documented in the literature on the fiber orientation at which a maximum in loss factor occurs can be resolved by incorporating the frequency dependence of the composite loss factor.
Surface modification of spectra™‐900 polyethylene fibers using RF‐plasma
Authors: Rostami Hossein , Iskandarani Bassel , Kamel Ihab 
Published: December 2004

AbstractRF‐plasma polymerization and bonding of allylamine onto ultrahigh molecular weight polyethylene (UHMWPE) “Spectra™‐900” is described using an inductively coupled plasma reactor. This process was found to enhance the interfacial strength between the fibers (Spectra‐900) and room‐temperature‐cured epoxy matrix up to fivefold. Fibers covalently coated with allylamine plasma showed no loss in tensile strength, while argon gas plasma pretreatment of the same fibers caused up to 10% reduction in tensile strength depending on the energy and duration of the treatment. Optimum treatment was attained through a short argon plasma etching (15 s), followed by allylamine polymerization and coating for 3 min. The coating process was found to protect the fiber surface from etching by plasma ion bombardment. A loss of 19% of the original diameter was found during the 15 s precoating etching with argon plasma, indicating the sensitivity of the fiber structure to plasma etching.
Whiskers and short fiber technology
Authors: Milewski John V. 
Published: December 2004

AbstractThis paper presents the technology of whiskers and short fibers for use in polymer substances. It starts with a definition and examples of what a whisker is and how it differs from other short fibers such as micro fibers, mineral fibers, chopped fibers, and milled fibers. Then this paper discusses the problems in working with whiskers and short fibers and gives solutions to these problems. Next, various ways of improving the efficiency of short fiber reinforcements is given. This is done by reviewing details of the theory of short fiber reinforcements and how the use of packing theory helps in making a better short fiber composite. Finally, suggestions are given for designing an idealized molding compound using whiskers and short fibers in harmony with good packing theories.
Modulus prediction of a cross‐ply fiber reinforced fabric composite with voids
Authors: Farouk A. , Langrana N. A. , Weng G. J. 
Published: December 2004

AbstractVoids or bubbles in polymer composites have a detrimental effect on the properties of the material. Such voids are found in PMR 15/graphite fiber (fabric type) composites. The matrix, PMR 15, is formed in‐situ during the molding process and undergoes two major stages of reactions, viz., imidization and crosslinking. Volatiles are formed as by‐products of these reactions and may remain trapped in the matrix to form voids or bubbles. Photomicrographs of composite cross sections suggested the classification of voids as two different phases in two different directions, each aligned with the fibers, resulting in a five phase model. The composites were tested in three‐point bending tests to obtain the flexural modulus. By combining Weng's inclusion approach (1) and Ishikawa and Chou's crimp method (2), an analytical model has been developed to predict the elastic moduli of such a multiphase composite material. Thus, the voids have been treated as inclusions in an enclosing matrix, which in turn is reinforced by woven fibers in two directions. The stiffness behavior obtained analytically was within 10% of the experimental values.
Theoretical determination of the optimal fiber volume fraction and fiber‐matrix property compatibility of short fiber composites
Authors: Pan Ning 
Published: December 2004

AbstractAlthough the question of minimum or critical fiber volume fraction, beyond which a composite can then be strengthened due to addition of fibers, has already been dealt with by several investigators for both continuous and short fiber composites, a study of maximum or optimal fiber volume fraction at which the composite reaches its highest strength has not been reported. The present analysis has investigated this issue for short fiber case based on the well‐known shear lag (the elastic stress transfer) theory. Using the relationships obtained, the minimum spacing between fibers is determined upon which the maximum fiber volume fraction can be calculated. The effects on the value of this maximum fiber volume fraction due to such factors as the mechanical properties of the fiber and matrix, the fiber aspect ratio, and fiber packing forms are discussed. Furthermore. Combined with the previous analysis on the minimum fiber volume fraction, this maximum fiber volume fraction is used to examine the property compatibility of fiber and matrix in forming a composite. This is deemed to be useful for composite design. Some examples are provided as well to illustrate the results.
Measurement of fiber orientation in short‐fiber composites using digital image processing
Authors: Gadala‐Maria F. , Parsi F. 
Published: December 2004

AbstractA technique that uses digital image processing to measure the orientation distribution function of the fibers in a plane of a short‐fiber composite is described in this work. Other orientation descriptors, such as the fiber orientation parameter, can be calculated from the measured fiber orientation distribution function. In this technique, the edges of the fibers in a digital image of the composite are first identified. Then, using Sobel operators, the orientation of the gradient vector is determined at each fiber orientation distribution function. The advantages of digital imaging over photography and the simplicity of the algorithms make this technique advantageous over previously developed methods to measure fiber orientation.
Fiber mat deformation in liquid composite molding. I: Experimental analysis
Authors: Han K. , Trevino L. , Lee L. James , Liou Ming 
Published: December 2004

AbstractWhen a resin in injected into the mold in liquid composite molding, the preplaced fiber mat may deform near the inlet gate because of the high momentum carried by the injected fluid. A fiber free region near the gate followed by the fiber mat deformation may emerge. This phenomenon is most likely to occur when the stacked fiber mats have low permeability and the resin has high viscosity. A set of mold filling experiments were carried out using an instrumented metal mold and a small transparent mold to investigate the fiber mat deformation during mold filling. Experimental results showed that the fiber mat deformation was limited to a small region near the gate and that deformation greatly reduced the molding pressure. A forced fiber mat deformation employing a modified gate design was proposed to facilitate mold filling in liquid composite molding.
Mechanisms of degradation of polymer composites by galvanic reactions between metals and carbon fiber
Authors: Woo E. M. , Chen J. S. , Carter C. S. 
Published: December 2004

AbstractToughened and untoughened epoxy and BMI carbon fiber reinforced composites were evaluated in terms of their matrix chemical stability in galvanic reactions between metals and composites. It has been known that the presence of moisture and salts and contact between unprotected metals and BMI carbon fiber composition constitute prerequisite conditions for composite degradation. This study has further demonstarated that these conditions were necessary, but not sufficient. It was found that the OH species generated by galvanic reactions had to be concentrated in localized spots to induce composite degradation at a significant rate. A mechanism was proposed to elucidate how degradation took place under those necessary conditions with the aid of localized aggregation of the OH−species. Additionally, thoughening of BMI composite matrix resins resulted in poorer resistance to degradation by galvanic reactions. On the other hand, none of the eposy composites (toughened or untoughened) exhibited any degradation due to galvanic reactions at room temperature, nor did they degrade in a concentrated caustic NaOH solution (pH = 14,82°C) that simulated a highly accelerated galvanie reaction.
Tensile mechanical properties and reduced internal stresses of polymer optical fiber
Authors: Bosc D. , Toinen C. 
Published: December 2004

AbstractA few years ago, polymer optical fiber (POF) emerged worldwide as a means for short optical transmission. This fiber type is generally made of poly(meth1 methacrylate) polymer and can be manufactured by a perform process using hot drawing in an oven. The mechanical properties, particularly the breaking stress, depend highly on the draw conditions. Recently, we have implemented the fabrication of very low diameter fiber, to take advantage of the electro‐optic properties of stumps of such single mode fiber. It turned out that the drawing conditions cause undesirable internal stresses, which, in turn, yield unfortunate refractive index variations in the fiber. We observed that increased shearing speed during the drawing operation of low diameter threads did provide high modulus fibers. To overcome the occurrence of the huge shrinkage at Tg, we have found that temperature and length of the oven are critical parameters: an increase in the temperature and also the length of the oven for a given drawing speed has resulted in quality POF.
Evaluation of fiber surfaces treatment and sizing on the shear and transverse tensile strengths of carbon fiber‐reinforced thermoset and thermoplastic matrix composites
Authors: Blackketter Donald M. , Upadhyaya Deepak , King Todd R. , King Julia A. 
Published: December 2004

AbstractThe mechanical performance of advanced composite materials depends to a large extent on the adhesion between the fiber and matrix. This is especially true for maximizing the strength of unidirectional composites in off‐axis directions. The materials of interest in this study were PAN‐based carbon fibers (XA and A4) used in combination with a thermoset (EPON 828 epoxy) and a thermoplastic (liquid crystal poymer) matrix. The effect of surface treatment and sizing were evaluated by measuring the short‐beam shear (SBS) and transverse flexural (TF) tensile strengths of unidirectional composites. Results indicated that fiber surface treatment improves the shear and trasverse tensile strengths for both thermosetting and thermoplastic matrix/carbon fiber‐reinforced unidirectional composites. A small additional improvement in strengths was observed as the result of sizing treated fibers for the epoxy composites. Scanning electron microscope photomicrographs were used to determine the location of composite failure, relative to the fiber‐matrix interface. Finally, the epoxy composites SBS and TF strengths appear to be limited to the maximum transeverse tensile strength of the epoxy matrix, while the thermoplastic composite SBS and TF strengths are limited by the LCP matrix shear and transverse tensile strengths, respectively.
On‐line consolidation of thermoplastic towpreg composites in filament winding
Authors: Wagner P. , Colton J. 
Published: December 2004

AbstractA study of the use of thermoplastic powder coated towpregs in filament winding was conducted. A suitable technique for manufacturing parts with adequate on‐line consolidation was identified through an experimental investigation that compared several techniques. This process utilized a single compaction roller on‐line consolidation head with hot air guns to obtain consolidation at the lay‐down point on the mandrel. The addition of a heated pultrusion die between the creel system and the filament winder was found to produce the best process. Nylon 11/E‐glass towpreg was used in this study. The effect of winding speed and compaction force on the quality of the resulting parts was determined in order to optimize the process. Only the speed was found to have a significant effect, with better quality parts being made at higher speed. Observations were also made on parts manufactured with polypropylene and E‐glass towpreg, as well as on parts wound with helical patterns.
Universal aspects of composite viscoelastic behavior
Authors: Sullivan J. L. , Wen Y. F. , Gibson Ronald F. 
Published: December 2004

AbstractThe viscoelastic behavior of a series of vinyl ester resins and E‐glass fiber‐reinforced composites is discussed. It is shown that the temperature shift factors for these systems, and others, suggests a universal behavior. A similar observation is made for the aging shift rate. On the other hand, the temperature dependence of compliance components per se appear to differ from system to system. Finally, it is shown that the retardation spectra for the vinyl ester resin and composites systems are the same to within a multiplicative constant in the glassy and in the short time transition regions. This shows that the presence of fibers has no influence on the distribution of retardation times in those regions.
Fracture toughness characterization of phenolic resin and its composite
Authors: Charalambides M. N. , Williams J. G. 
Published: December 2004

AbstractThe aim of this study is to determine the fracture toughness of phenolic resin and its composite. Fracture tests on phenolic resin resulted in a fracture toughness close to values quoted for unmodified epoxy resins. Composite specimens of glass fiber reinforced phenolic were also tested. The interlaminar fracture toughness in both mode I and mode II failures was determined. The mode I initiation values were lower than the neat resin's toughness. Mode I propagation values were strongly influenced by fiber bridging. The mechanism of fiber bridging was found to be sensitive to specimen dimensions. The effect of fiber bridging on the mode I analysis is discussed. Fiber bridging was also evident in mode II failures. Two different geometries were used for the mode II tests (end loaded split and end notched flexure); a correlation between the results from the two geometries is made.
Experimental investigation of fatigue crack growth behavior and damage mechanisms of fiber/metal laminates under uniaxial and biaxial loading
Authors: Li K. , Chudnovsky A. , Kin Y. , Macheret J. 
Published: December 2004

AbstractThe response of the aramid reinforced aluminum‐epoxy‐laminate to uniaxial and biaxial fatigue loading has been investigated. The fracture process in the laminates propagates mainly in the form of cracks in aluminum layers, delaminations between the resin‐rich and fiber‐rich prepreg layers, splitting in prepreg layers and fiber fracture. Ultrasonic microscopy has been used to evaluate the shape and size of the damage zone. The ultrasonic images have been calibrated by means of SEM and optical microscopy of the laminates with sequential removal of the layers. Microscopic examination reveals a direct correlation between delamination, fiber fracture, and fatigue crack growth in the aluminum layer. The results of this investigation strongly suggest that the laminate resistance to tension‐tension biaxial fatigue is superior to that under uniaxial loading conditions.
Bending strength of composite laminates with an elliptical hole
Authors: Zhao Yi , Tripathy Aruna K. , Pang Su‐Seng 
Published: December 2004

AbstractGreat efforts have been made in analyzing the strength of notched laminates under in‐plane loadings. However, no work has been reported on notched laminates under bending, because of the complexity of theoretical stress analysis. In this study, a simplified approach has been used to analyze the notched strength of laminated composites with an elliptical hole under bending. This approach combines notched sample experiments and finite element results. Based upon the consideration that not only the stress distribution at one ply, but also the stress variation across the laminate thickness, should be taken into account, two failure models are presented: a modified point stress model and a modified average stress model. Two characteristic parameters are presented to evaluate the notched strength of the laminated plates.
A finite element method for flow in compression molding of thin and thick parts
Authors: Liang Erwin W. , Tucker Charles L. 
Published: December 2004

AbstractBased on Barone and Caulk's model and a generalized variational functional, a finite element simulation was developed for the compression molding of thin and thick parts. For solving the u‐v‐p type equations, an element‐based penalty method and a mixed formulation were implemented. Numerical results show that the new model gives better accuracy in velocity and velocity gradient than the Hele‐Shaw formulation for cases where both models are appropriate. Predictions of velocity and its gradient by the model are compared with other FEM results and BEM solutions. Using a fixed base mesh that covers the mold cavity, a new technique was developed for tracking the moving flow front. Temporary elements and nodes are generated for the filled part of elements intersected by the flow front. This method allows a smooth representation of the flow front and has exact boundary conditions on the flow front. The scheme is demonstrated for compression molding of an elliptical and an L‐shaped charge.