摘要:

AbstractRegular symmetrical laminates of the {+α/−α/+α/−} sym. type were manufactured and tested using established methods. Tensile characteristics—elastic modulus and the ultimate stress/strain characteristics—were determined in the form of angular dependences on the ply‐angle α. The same mechanical properties were also simulated adopting a reported theoretical model. The correlation between the experimental and the predicted values shows an excellent agreement for the laminate stiffness. On the other hand, the fit for the ultimate properties was unsatisfactory except under conditions of linear, elastic response encountered for α→ O and 90°. Generally, a qualitative correlation has been obtained for the ultimate strength, but no relation has been established for the ultimate strain. A mechanism of fiber reorientation during loading, i.e. closing of the ply angle with the increasing strain has been found to be responsible for exceptionally non‐linear stress‐strain response in the range 30<α<60°. Coupon width and strain rate have both been found to have little effect on

ISSN:0272-8397    

DOI:10.1002/pc.750130302

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe mechanism of damage accumulation and failure in thin sheets of an orthotropic long discontinued glass fiber reinforced polypropylene composite was studied using optical and electron microscopy coupled with acoustic emission (AE) monitoring. The effect of strain rate (0.1 to 100 percent) was investigated, and a close correspondence was established between AE response and microscopic observations. Furthermore, simultaneous AE monitoring and optical microscopy performed during sample deformation substantiated the assignment of certain AE amplitude ranges with specific failure events in the composite. Specifically, the failure process was found to be very inhomogeneous in nature, and could be divided into three main stages of damage accumulation. Finally, cumulative AE energy curves were found to follow an interesting powerlaw behavior. Results based on the coupling of AE methods with optical and electron microscopy were found to be self consistent and in agreement with previous reports on thicker‐section composites manufactured from the same material

ISSN:0272-8397    

DOI:10.1002/pc.750130303

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractMechanical properties of fiber reinforced composites depend on the formation of stable adhesive bonds between the constituents. In order to evaluate quantitatively the adhesion between liquid crystal polymer (LCP) fibers and a thermoplastic matrix of polycarbonate, the single fiber composite test (SFC), utilized for testing glass or carbon fiber composites, has been used. Neither chemical nor physical interaction has been found: the PC and LCP phases are completely incompatible. However, a mechanical friction between PC and LCP was observed during the drawing of the sample when the neck of the matrix started.

ISSN:0272-8397    

DOI:10.1002/pc.750130304

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

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 agen

ISSN:0272-8397    

DOI:10.1002/pc.750130305

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

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

ISSN:0272-8397    

DOI:10.1002/pc.750130306

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe cure kinetics of two dicyanate resins were investigated by differential scanning calorimetry under isothermal and nonisothermal conditions. An autocatalytic kinetic model was proposed and a set of general kinetic parameters was calculated from the isothermal experiments. Good agreement between experimental data and the kinetic model has been obtained under different processing conditions, which demonstrated the validity and the usefulness of the analytical procedure and of the kinetic expression employed. Consequently, in its current form, the modeling methodology is capable of describing the degree of cure during a typical processing cycle and has the potential for comparing different resin formulations as well as the manifestations of cure in property development. Specifically, in this work the modeling methodology was tested using two distinct dicyanate resin systems while the development of the cure was also observed through dielectric analysis (DEA).

ISSN:0272-8397    

DOI:10.1002/pc.750130307

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractAs part of an engineering analysis and experimental methodology to characterize prepreg tack, a compression‐to‐tension test was optimized to enhance reproducibility and generate intrinsic property data. With the resulting stress‐strain compression and tension data, a theoretical model was developed to describe tack as a bulk viscoelastic property of a prepreg laminate stack. Using the viscoelastic analysis, four intrinsic material parameters to characterize prepreg tack could be defined. These were 1) relaxed modulus, 2) unrelaxed modulus, 3) relaxation time, and 4) initial void content of the prepreg stack. Relaxed and unrelaxed moduli of the prepreg stack were independent of temperature, while the relaxation time was highly dependent on temperature and matrix viscosity. In addition, the relaxation time was found to be influenced by resin/fiber content and prepreg surface characteristics, which also influenced the void content of the prepreg stack. Using these measured parameters, good agreement was observed between theory and experimental data for both the stress‐strain curve of the tack test and the simplified compression tack index (CTI*), defined as the ratio of output energy of the prepreg stack during tensile unloading to input energy during compressive

ISSN:0272-8397    

DOI:10.1002/pc.750130308

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

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

ISSN:0272-8397    

DOI:10.1002/pc.750130309

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effects of additives such as boron trifluride‐monoethylene amine (BF3MEA) and fumed silica in the TGDDM/DDS epoxy formulations on the curing properties, resin contents, and mechanical properties of their graphite/epoxy (Gr/Ep) composites were investigated. The addition of BF3MEA increased the viscosity of resin as well as the resin contents of cured laminates because of its catalytic effect. Although the fumed silica was considered a thickening agent, it also acted like a co‐catalyst with BF3MEA. As the resin content of cured laminates was increased, the excess resin was likely to accumulate in the interlaminar region, which increased the interlaminar shear strength but decreased the flexure strength as well as the interlaminar fracture toughness value,

ISSN:0272-8397    

DOI:10.1002/pc.750130310

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

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.

ISSN:0272-8397    

DOI:10.1002/pc.750130311

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY