摘要:

AbstractA process for producing long‐fiber‐reinforced thermoplastic matrix composites is described. This process, based on papermaking technology, consists of depositing a mixture of a polymeric powder and reinforcing fibers from an aqueous slurry. The degree of homogeneity of the mixture and the subsequent ability to handle the dried sheet have been significantly improved by the addition of less than 5% pulp fibers, based on solids concentration, to the slurry. The dried sheet is then consolidated into a composite sheet with a continuous matrix phase by the application of heat and then pressure. Tensile properties and the degree of reinforcement efficiency of composites produced by this process have been shown to be comparable to those produced by melt impregnation techniq

ISSN:0272-8397    

DOI:10.1002/pc.750100302

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractSamples of Narmco Rigidite 5208/WC3000 carbon‐epoxy prepreg were exposed to ambient temperature (22°C) and 50% relative humidity for different periods up to 66 days. They were analyzed in depth using various techniques to determine the extent of the chemical changes occurring. The physicochemical techniques used were Fourier transform infrared spectroscopy (transmission, attenuated total reflection, diffuse reflection), liquid chromatography (reverse‐phase, high‐speed reverse‐phase, and high‐performance size‐exclusion), thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and pyrolysis‐gas chromatography. All showed evidence of significant changes, the most sensitive being Fourier transform infrared spectroscopy (FT‐IR) and reversephase liquid chromatography (RPLC). FT‐IR showed that the number of unreacted epoxy groups decreases steadily at a rate of 0.34% per day, based on the initial amount. At the same time, the number of free amine‐hardener molecules, as monitored by RPLC, drops at a rate of 1.05% per day. RPLC also showed that the amount of initial epoxy‐amine reaction product increases significantly over the first 30 days, but then declines as it undergoes further reaction to give higher‐molecular‐weight products. The heat of polymerization of the resin, measured by thermal analysis, decreased by 0.26% per day from it

ISSN:0272-8397    

DOI:10.1002/pc.750100303

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractElectrocopolymerization of acrylonitrile/methyl acrylate/acrylic acid, acrylonitrile/methylacrylate, and glycidyl‐acrylate/acrylonitrile interlayers onto Hercules AS4 graphite fibers was used to improve simultaneously the effective interfacial shear strength, τe, and the fracture toughness of graphite‐epoxy composite materials. With a single‐fiber fracture test, τefor these coated fibers (embedded in a diglycidyl ether of bisphenol A ‐ 4,4′‐methylenedianiline matrix) was determined at various temperatures and under various hygrothermal treatments. At room temperature, the coated samples showed slightly improved shear strength over the uncoated sample. At elevated temperatures, a plot of τevs. temperature for the uncoated sample showed two distinctive regions: an interface‐controlled plateau region at low temperatures, and a matrix‐controlled region at high (>80°C) temperatures. Only one region, which was controlled by the matrix and the interlayer, was observed for the GA/AN coated sample. The τevalues determined were slightly higher than the shear strength of the bulk matrix, possibly because of stronger matrix properties at the interface. Optical micrographs of the coated sample tested at temperatures less than 100°C showed no matrix crack perpendicular to the fiber axis, indicating that the interlayer has effectively blunted the crack tip and restricted its propagation. The effect of moisture in the sample was to reduce τefor the coated sample. Upon dehydration, the strength was partially recovered. The treatments did not affect the uncoated sample, however. The fragmentation length data were fitted well by both Gaussian and

ISSN:0272-8397    

DOI:10.1002/pc.750100304

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of curing conditions on the low temperature relaxation behavior of catalyst‐cured epoxy systems based on digliycidyl ether of bisphenol A (DGEBA) has been characterized by the thermally stimulated discharge current (TSDC) technique. In these chemically relatively simple epoxy systems, five relaxation processes, designated as γ, β, β′, βOH, and β″, have been observed: Their molecular origins are discussed in detail. The results are in agreement with prior suggestions of an inhomogeneous cross‐link densit

ISSN:0272-8397    

DOI:10.1002/pc.750100305

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractMultiple gating and the presence of inserts make weld lines (also known as knit lines) almost unavoidable in commercially produced moldings. These weld regions may be significantly weaker in strength than the bulk material away from the weld line. Hence, a molded section containing a weld line will only be as strong as the weld line, no matter how strong the surrounding bulk material. The influence of processing history on weld line performance is essential to optimally designed transfer‐molded composite products with discontinuous‐fiber‐reinforced molding materials. This study has therefore been directed toward experimentally characterizing the weld line strength of a bulk molding compund (BMC) and a thick molding compound (TMC) as a function of the mold temperature, fill time/fill rate, and the postbake oper

ISSN:0272-8397    

DOI:10.1002/pc.750100306

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractA new way is introduced to express the interaction coefficient characterizing the surface activity of fillers. The interaction coefficient is a parameter showing how many times greater a specific interaction of a testing solute with a filler surface is than a nonspecific interaction of a hypothetical alkane with the same vapor pressure. A selectin of testing solutes for the determination of the interaction coefficient is discussed. Due to a high surface activity of the studied fillers for polyolefine composites, less polar solutes (furan, dichloromethane, trichloromethane, and benzene) have been selected to study these fillers. New evaluation coefficients of acidity, basicity, and acidobasicity are proposed for a rapid activity determination of a filler surface. These coefficients can be determined from a single chromatogram of the testing solutes. The surface activity of various fillers (calcium carbonate, talc, magnesium hydroxide), as expressed by the interaction coefficient, differs so much that even the differences of surface activities in one filler type (calcium carbonate), dependent on the origin or arrangement, are conclusive.

ISSN:0272-8397    

DOI:10.1002/pc.750100307

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractThe role of inner‐layer (interphase) in fiber‐reinforced composites is often assessed by measuring the interfacial shear strength of single fibers embedded in matrix blocks. Interfacial shear strength is calculated using simple shear lag analyses (Kelly and Tyson model). This paper shows that application of Kelly and Tyson's equation may result in gross overprediction of interfacial shear strengths if the thickness of the inner‐layer is not negligible in comparison with the fiber dia

ISSN:0272-8397    

DOI:10.1002/pc.750100308

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750100309

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750100310

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750100301

出版商:Society of Plastics Engineers    

年代:1989

数据来源: WILEY