摘要:

AbstractPolypropylene/low density polyethylene blend matrices have been reinforced with short glass fibers in order to study their tensile, flexural, and impact behavior. Two‐roll milling and twin‐screw extrusion compounding methods were used to incorporate the fiber within the polymer matrices, and standard test samples were prepared by injection molding. The effects of matrix composition and fiber concentration on mechanical properties were investigated keeping in mind the matrix and fiber morphology, the latter being intimately dependent upon the compounding method emplo

ISSN:0272-8397    

DOI:10.1002/pc.750120102

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe morphology of short glass fiber reinforced composites based on polypro‐pylene/low density polyethylene (PP/LDPE) blend matrices was investigated by means of an optical microscope as a function of both matrix composition and fiber content. The influence of compounding and processing methods was also studied. The LDPE content hardly affects the morphology of the blends, at least within the range of percentages that have been investigated (5 and 10% by weight). On the other hand, glass fibers obstruct the matrix spherulitic development. The blend morphology is strongly affected by the processing method and the compression molded blends show larger spherulitic size than the injection molded ones. Scanning electron microscopy showed the fiber orientation across the injection molded composite

ISSN:0272-8397    

DOI:10.1002/pc.750120103

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractIn many reinforced composite manufacturing processes it is necessary to compact the fiber materials to obtain the desired fiber/resin ratio in the finished part. Detailed knowledge of applied surface force versus material fiber volume is particularly important in processes such as pultrusion, resin transfer molding, and compression molding. The force required to compact a stack of reinforcing material is strongly dependent on the type of fiber used and its material form. Complicated interactions are possible, particularly when mixtures of unidirectional, oriented cloth and random fiber mats are used. This paper will present results of an experimental and analytical investigation of the response of various dry reinforcing materials subjected to compressive forces applied normal to their principle plane. Experiments were conducted by applying up to 8.6 MPa normal force to thick stacks of E‐glass, graphite cloth, mat and unidirectional material and combinations of two different fiber orientation. Pressure versus fiber volume data were generated for both individual materials and various combinations. Experimental results were compared to analytical predictions. Data showed that the force versus deformation is very strongly dependent on the details of the fiber form or forms being used. There is structural relaxation during fiber compression. Relaxation is very related to fiber orientation, span length, and fiber breakage during compaction. Relaxation behavior decreases with fiber alignment. Random mats and 0/90 cloth show much more relaxation than unidirectional fibers. Data of relaxation is very well fitted with a Maxwell‐Wiechert viscoelastic mo

ISSN:0272-8397    

DOI:10.1002/pc.750120104

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

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 stac

ISSN:0272-8397    

DOI:10.1002/pc.750120105

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThis work presents the results of numerical simulation and experimental visualization of the mold filling process in resin injection molding with preplaced fiber mats. The mold filling experiments were conducted with various mat stacks consisting of continuous random glass fiber mats and bidirectional stitched glass fiber mats. The use of two different mat types in the mat stack created porosity and permeability variations. The effect of these permeability 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. Numerical simulation corresponding to each experiment was also carried out. The numerical results were compared to the experimental measurement

ISSN:0272-8397    

DOI:10.1002/pc.750120106

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper reviews the basic theoretical approach to describing light scattering in filled materials with nearly matching refractive indices (Rayleigh‐Gans‐Debye Theory). The modifications necessary to handle high filler concentrations (interparticle interference and multiple scattering) are included empirically. The primary result of this analysis is an expression for the optical transmission of a polymer composite as a function of particle size, volume fraction, composite thickness, and refractive index difference between the components. The angular dependence of the scattering is included so that scattered light which falls within the aperture of the transmission detector can be accounted for, Particular attention is given to including the temperature dependence of the refractive index and the effect of fillers on the thermal expansion properties of the polymer matrix in order to predict the temperature range over which the composite will be optically useful. Similarity to analyses of the Christiansen filter is discus

ISSN:0272-8397    

DOI:10.1002/pc.750120107

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractExperiments were conducted to determine the dependence of the interfacial shear strength on the bulk material matrix properties using model compounds based on epoxy/amine chemistry. AS4, carbon fibers were used as the subject for these measurements with both a difunctional epoxy (DGEBA) system as well as a tetrafunctional epoxy (MY720) system. Amine curing agents were carefully chosen to produce matrices which produced a range of matrix properties from brittle, elastic to ductile, plastic. The fiber‐matrix interfacial chemistry was constant throughout this study by always using a stoichiometric amount of curing agent. The results indicate that, for both the difunctional as well as the tetrafunctional epoxy system, the interfacial shear strength (as determined by the fragmentation test) decreases nonlinearly with decreasing modulus of the matrix. Linear elastic analysis yields a nearly linear relationship, for both systems, between the interfacial shear strength and the product of strain to final break and the square root of the matrix shear modulus. A linear relationship is also found between the difference in test temperature and glass transition temperature of the cured matrix and the interfacial shear strength. Additionally, the failure mode is seen to remain interfacial as the ductility of the matrix change

ISSN:0272-8397    

DOI:10.1002/pc.750120108

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractMechanical properties and microscopic fracture mechanisms of continuous fiber reinforced polymer composites were investigated. Perforated polyimide films (e.g. Kapton®) were added between composite prepreg layers to modify the interlaminar bonding strength. Addition of highly perforated films can increase the toughness of unidirectional glass/epoxy composites without an appreciable reduction in strength. The fibrous composites studied exhibit two fracture modes (compressive and tensile) when failed by three‐point bending. In general, the compressive failure mode preceded the tensile failure mode. Real‐time acoustic emission (AE) analysis was found to provide more fracture information which is otherwise not discernible from mechanical testing alone. The crack initiation stress level and the subsequent crack propagation mode were identified by real‐time AE during deformation and by post‐failure scanning electron microscopy fracture surface

ISSN:0272-8397    

DOI:10.1002/pc.750120109

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA dynamic mechanical apparatus, based on the concept of mechanical impedance analysis (MIA), was constructed for real‐time cure monitoring of composites. The frequency response function (FRF), in terms of the inertance, impedance or admittance value, can be obtained from the ratio of the Fourier Transforms of excitation and response signals. Spectra during curing of several different kinds of composite materials were obtained with the Fast Fourier Transform spectrum analyzer while the material was continually excited with a random input generated by an electro‐magnetic shaker. The dynamic properties, such as storage modulus (E′) and loss tangent (tan δ), of the composite can be obtained from the FRF spectra as a function of cure time and temperature. Variations of the inertance spectra with cure time, reflecting the changes in the dynamic mechanical properties, for the composite materials under various isothermal cure conditions are discussed. Optimal cure cycles of a new resin can be determined by characterizing the phase transformation of the material, which can be identified from the MIA measurement results. The MIA technique is found to be a sensitive and direct means for monitoring the overall cure state of composites. The signals obtained can be integrated in real‐time in a closed‐loop feedback control system for composite f

ISSN:0272-8397    

DOI:10.1002/pc.750120110

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractOne sided copper glass/epoxy laminates for printed circuit board (PCB) applications were examined using an instrumented puncture impact technique. The effect of the diameter of the support ring, the initial impact velocity, and the preence of a stress concentrator on the impact parameters were evaluated. The orientation of the copper film with respect to the impacter was also varied. The PCB laminate showed brittle failure under the different conditions examined. Results showed that a higher degree of toughness was found for the condition where the copper layer was directly impacted by the dart. The maximum force and the total impact energy were found to be independent of the strain rate. The effect of a stress concentrator on the impact parameters was also found to be minimial. Total impact energies were found to be in the range of 8.8 to 12.6 J for the different testing conditions.

ISSN:0272-8397    

DOI:10.1002/pc.750120111

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY