摘要:

AbstractThe interaction between the fiber and matrix in a fiber‐reinforced material plays an important role in determining the mechanical behavior of the composite. An efficient technique to simultaneously improve fiber‐matrix interfacial shear strength and impact behavior of the composite is to deposit a flexible interlayer onto the fiber. This results in the creation of three bulk phases, the fiber, matrix, and the interlayer and two interphasial regions. A phenomenological model that defines the variation of the fiber‐interlayer interphase and that of the interlayer‐matrix interphase has been developed. In the model, the elastic moduli of these regions vary continuously, so as to bridge the two bulk phases on either side of the interphase. The interaction between the bulk phases is also taken into consideration. The model has the potential for the use of dynamic mechanical analysis to obtain, relatively, adhesion/interaction parameters of different fiber‐interlayer‐matrix systems. These parameters can be used to determine the optimum interlayer thickness for improved toughness and good stress transfer

ISSN:0272-8397    

DOI:10.1002/pc.750120602

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractExperimental results are reported on the electrical properties of glass‐laminated unsaturated polyester (UP) resins. Measurements of the poling current as a function of temperature reveal two different activated processes. Above 50°C the activation energy is 160 kJ/mol and has been associated with ionic condition, possibly by protons, while at lower temperatures (below −70°C) the activation energy is very low (less than 40 kJ/mol) and is associated with dipole relaxation. It is concluded that the laminated UP resin undergoes a phase transformation between low and high temperatures, which gives rise to a completely different electrical response. This phase transformation can be associated with the glass transition of UP resin phase. In view of the low activation energy, giving rise to a polarization peak, it is concluded that the low temperature range (glassy state) favors strictly localized motions of charges—most likely electrons. At higher temperatures, the behavior corresponds to d.c. conductivity and is associated with extended motions of charge carriers with limitations at contacts and at internal barriers. According to the air gap measurements, the pronounced dip found in the temperature dependence of the poling current (in the range from 20 to −30°C) may be due to separation of conduction and dipole relaxation current. Thermally stimulated depolarization (TSD) current measurements reveal the presence of high internal fields due to space charges accumulated at the phase boundaries of gl

ISSN:0272-8397    

DOI:10.1002/pc.750120603

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe primary goal of this study was to develop 2‐D and 3‐D computer simulation schemes for the mold filling processes of structural reaction injection molding (SRIM) and resin transfer molding (RTM) under isothermal conditions. The developed computer code was able to simulate the mold filling in molds with complicated geometry, Experiments were also carried out based on flow vitalizations. Experimental results were compared with the numerical simulati

ISSN:0272-8397    

DOI:10.1002/pc.750120604

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe application of rapidly solidified amorphous metal ribbons as continuous reinforcements for thermoplastic composites is examined. The metallic glass alloy Fe40Ni40B20(at. percent), with good stiffness, strength, and magnetic properties, was selected as the ribbon alloy. The mechanical properties of the ribbons (elastic modulus and fracture strength) were determined by tensile testing under plane‐stress conditions. The continuous FE40Ni40B20amorphous ribbons were incorporated as reinforcements into a polypropylene (thermoplastic) matrix. To evaluate the quality of the composites formed, ribbon pullout tests were performed to measure the interfacial ribbon/matrix bond strength. It was noted that increasing the hot compaction pressure during fabrication and the surface texture of the ribbons by etching significantly improved the interfacial shear strength between the ribbon and thermoplastic matri

ISSN:0272-8397    

DOI:10.1002/pc.750120605

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractComposite specimens with polypropylene matrix containing up to 1.8 percent volume fraction of amorphous metallic ribbons with the interfacial shear strength ∼0.7 MPa were fabricated by hot compaction under 10 MPa pressure. Their tensile properties and fracture behavior were investigated. It is found that within the investigated range of the volume fraction of reinforecement the composite fracture strength is close to the rule of mixtures predictions. Two types of fracture, matrix and ribbon controlled, are observed. The experimental values of the composite elastic modulus are also close to the rule of mixtures prediction

ISSN:0272-8397    

DOI:10.1002/pc.750120606

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractCommingled fabrics composed of yarns containing both the reinforcement and the matrix in fiber form are an innovative preform for thermoplastic composite materials. The material is consolidated into a rigid structure by the application of heat and pressure. A mathematical model of the consolidation process for commingled fabrics has been developed. The model predicts the variation of laminate thickness, fiber volume fraction, and void content during the consolidation process as well as the time required to reach full consolidation. Materials composed of initially separate, commingled or cowoven fiber bundles are considered. The influence of fiber velocity induced by compaction on the flow of matrix is accounted for. An equivalence factor has been derived so that a one‐dimensional flow analysis may be used to model the impregnation of elliptical bundles of varying aspect ratio. This permits an analytic solution to the governing equation for fiber bundle impregnation. The model was utilized to examine the influence of various material and processing parameters on consolidation behavio

ISSN:0272-8397    

DOI:10.1002/pc.750120607

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe dynamic mechanical relaxation behavior of poly(methyl methacrylate) reinforced by continuous parallel Kevlar‐49 fibers is investigated here on samples with several fiber volume fractions. The shifts in the temperature of the main relaxation of the matrix are interpreted according to free volume considerations and with the help of a thermomechanical block model. The dependence of the storage and loss moduli both on temperature and fiber content found experimentally can be reproduced by the model. It is not necessary to rely on the existence of an interphase to account for the modifications evidenced by the spectrum of the matrix, which can be explained on the basis of the two phase mode

ISSN:0272-8397    

DOI:10.1002/pc.750120608

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA continuously monitored single‐filament composite (CM‐SFC) test was conducted to measure the stress at which successive fiber breaks occur in the single fiber fragmentation process. This exercise was performed with a limited number of samples of various types. The purpose was to explore the possibility of using this test as a simple alternative means of (i) measuring the size effect in single fibers, (ii) calculating the Weibull shape and scale parameters for fiber strength, (iii) calculating the fiber/matrix interfacial shear strength from the extrapolated value of fiber strength using the loading history of a single fragmentation test, rather than from the value of fiber strength extrapolated from extensive testing of single fibers at various gage lengths, as is usually done. These are aspects of the SFC test that have largely been ignored so far. The results presented here confirm the possibility of using the CM‐SFC test for such purposes, with a certain degree of approximation, as discussed. Additional information supplied by this test as well as a possible effect of fiber pre‐tensioning on fragmentation results (including the value of the interfacial shear strength) are also briefly di

ISSN:0272-8397    

DOI:10.1002/pc.750120609

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA method has been developed for studying the distribution of fillers and reinforcement in polymer composites by energy dispersive analysis of X‐rays (EDAX). Conventional methods for such studies are based on the morphological examination of the contrast in the micrographs, which indicates the presence and distribution of reinforcement in a matrix. However, in case of hybrid composites, where two or more fillers of similar morphology are present, the conventional methods fail. The approach described here overcomes this limitation and provides a new semiquantitative method of identification of fillers in composites, especially those containing two or more fillers of similar morpholog

ISSN:0272-8397    

DOI:10.1002/pc.750120610

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750120601

出版商:Society of Plastics Engineers    

年代:1991

数据来源: WILEY