摘要:

AbstractThe dynamic mechanical properties of composite materials, consisting of an epoxy matrix filled with iron particles, were determined over a temperature range. The storage‐ and loss moduli were evaluated in a Dynastat apparatus, with the parameters being the volume fraction of filler and the test frequency. A theoretical model was developed for comparing the experimental results with the theoretical predictions. A satisfactory correlation was obtained for the glassy region of the composit

ISSN:0272-8397    

DOI:10.1002/pc.750070102

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractGlassy composites were made by photopolymerization of a dimethacrylate paste containing silanated silicate particles (up to 50 μm). Minimum values of Vickers hardness number, stiffness, and yield stress were found for volume fractions of the filler in the range 0.03 to 0.05. Generally fracture surface morphology resembled classical results for inorganic glasses. In addition, tracks and features were observed of the kind reported previously for highly crosslinked organic glasses. Such morphology has been attributed to fortuitous changes in direction of the principal tensile stress just ahead of the crack tip. In the present work it was found that single tracks and features were associated with individual filler particles. This observation is consistent with the expectation that individual particles would act as stress concentrators and thereby serve to change the direction of the principal stress. Furthermore, stress concentration may be invoked to account for the minimum in mechanical properties but dewetting might also be involved

ISSN:0272-8397    

DOI:10.1002/pc.750070103

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractResin cross‐flow during compression molding of unidirectional sheet molding compound composites, such as CSMC and XMC, may cause severe misorientation of the continuous fibers in the outer layers. The extent of fiber misorientation depends on the type of molding compound, the length of cross‐flow, and the location of the charge in the mold. The tensile strength is reduced in the direction of cross‐flow with decreasing mold surface coverage. However, since severe fiber misorientation is generally restricted to the outer layers, increasing the number of plies improves the tensile strength to the level observed with little or no misorient

ISSN:0272-8397    

DOI:10.1002/pc.750070104

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractExperiments on sphere‐filled aligned fiber reinforced polyester resins show that the Young's and flexural moduli of the composites are increased by the presence of the spheres. The increase is particularly marked for composites made with flexible resins, and has potential for improving the properties of aligned fiber laminates. The moduli in the absence of fibers do not fit well with existing theory, and agreement with finite element analysis is only observed in the case of the rigid polyester. When fibers are present synergistic effects are observe

ISSN:0272-8397    

DOI:10.1002/pc.750070105

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect on packing resulting from the filling of unsaturated polyester resin with fillers and jute fibers has been investigated. The influence of absorbed water on the interfacial interactions involved in the fiber matrix system of the jute reinforced polyester resin also are discussed. An approach to reduce water absorption and soluble matter lost from the jute reinforced polyester resin is proposed.

ISSN:0272-8397    

DOI:10.1002/pc.750070106

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractAcoustic emission (AE) during irreversible deformation in short glass fiber reinforced poly(vinyl chloride) (PVC) composites was studied using a piezoelectric crystal transducer. Compared to the well‐coupled composites, many more AE events were observed during tensile deformation in the poorly‐coupled composites, presumably due to failure at the fiber‐matrix interface. No fiber fracture was detected in the tensile tests for either well‐coupled or poorly‐coupled composites. Irreversibility of acoustic emission was observed in repeated tensile loading experiments. Unlike PVC, the short fiber composites fractured during stress relaxation at 1 percent elongation. Studies of acoustic emission behavior during stress relaxation indicated that interfacial debonding is a time‐dependent process. Relaxation fracture time was strongly increased by chemical coupling at th

ISSN:0272-8397    

DOI:10.1002/pc.750070107

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe elastic and yield properties of drawn poly(methyl methacrylate) (PMMA) filled with ultrafine SiO2are described as functions of filler content and size. The drawn PMMA composites were made by uniaxially drawing to x4.0 at 100°C and at a rate of 20 mm/min. Four compliance values, i.e.,S33,S11,S13, andS44were determined. These values decreased with filler content and decreasing filler size. The relative compliance valuesSde/Sdo(Sdeis the compliance of drawn PMMA composites andSdois that of drawn unfilled PMMA) are almost equivalently changed with changes in filler content. The elastic properties of drawn PMMA composites are thus reinforced isotopically. This is characteristic of PMMA which has a large side group. The yield behavior of drawn PMMA composites have similar filler size and content dependence to those of elastic properties except that the transverse yield stresses become more brittle with filler content. The anisotropy in yield stress is relatively larger than that of elastic properties. This is probably because the anti‐reiforcing effect, such as fibrillation becomes prominent with increasing filler content in the perpendicular directi

ISSN:0272-8397    

DOI:10.1002/pc.750070108

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractPolypropylene composite samples with concentrations of mica of 10, 20, 30, 40, 45, 50, and 60 wt percent were prepared under identical conditions by injection molding. The influence of mica concentration on the structure and mechanical properties of the composites was investigated using a polarizing microscope, scanning electron microscope, differential scanning calorimetry, and stress‐strain characteristics. Flexural and impact strengths show an initial rise and then gradual fall with increasing mica concentration. An optimum of these properties occurred at ∼20 wt percent mica. Tensile modulus and heat distortion temperature show a continuous rise; whereas the percent elongation decreased with mica content. These changes in properties are discussed in terms of a skin‐core morphology, transcrystallinity, crystallinity, fracture surface morphology, flake orientation, and interfacial adhesion in these composites. This study helps in optimizing the mica concentration for injection molded compo

ISSN:0272-8397    

DOI:10.1002/pc.750070109

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe hydrodynamics and heat transfer that take place during molding of short fiber polymer composites have been analyzed. Consequently, the fiber orientation development has been qualitatively modeled and the flow mechanisms that contribute to fiber orientation have been identified: 1. Spreading radial flow in the vicinity of the cavity gate, originates transverse orientation of fiber with respect to the flow direction. 2. The fountain flow in the advancing front contributes to orientation of fibers in the surface layer in the flow direction. 3. Converging type flow, as the melt front flattens, causes some alignment in the flow direction. 4. Shear flow, which in the nonisothermal case, contributes to fiber orientation in the flow direction, at some distance from the wall. As a result of these mechanisms a layered structure is formed, having distinct fiber orientations. The experimentally observed fiber distributions in injection molding of thermoplastics, transfer, and compression molding of thermosets, agree with the qualitative predictions. The suggested orientation mechanisms may guide the mold and product designers as to the effect of gate location, mold dimensions, and processing variables on the final properties of the article.

ISSN:0272-8397    

DOI:10.1002/pc.750070110

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe influence of temperature on the impact behavior of unidirectional glass fiber‐epoxy composite was studied in the range of −20 and 150°C using a 3‐point drop weight test at a constant impact velocity of 2.2 m/s (5 mph). The impact energy per unit deformed volume was found to be very sensitive to the ratio length/thickness of the specimens. When the ratio was 4, the impacted specimens exhibited extensive delamination (shear failure) and the energy absorbed by the composite was about 14 MJ/m3between −20 and 100°C, and 18 MJ/m3at 150°C. At length/thickness above 16 the failure was mostly in tension, and the impact energy approached a constant value of about 3.5 MJ/m3, independent of t

ISSN:0272-8397    

DOI:10.1002/pc.750070111

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY