共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Merijs Meri T. Bocoka J. Zicans M. Kalnins V. Kalkis A. K. Bledzki 《Mechanics of Composite Materials》2008,44(4):361-370
Changes in the toughness of crystalline poly(ethylene terephtalate) upon addition of two elastomers — ethylene-propylene-diene
terpolymer and ethylene-α-octene copolymer — are investigated. Blends with increasing elastomer content (up to 30 wt.%) were obtained and modified
by γ-radiation up to a 300-kGy absorbed dose. The interrelation between the toughness and certain tensile characteristics (elastic
modulus, yield stress, ultimate stress, elongation at break, and specific fracture energy) of the blends, with various structural
features of components (crystallinity and the degree of cross-linking) and morphology of the blends, is discussed.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 521–534, July–August, 2008. 相似文献
2.
S. B. Sapozhnikov A. N. Aniskevich V. A. Tsarevskii 《Mechanics of Composite Materials》2006,42(6):571-576
A numerical method for predicting the deformational and strength characteristics of a calcite-quartzitic polymer concrete
from the known properties of its components is developed based on the finite-element method. Components of the material are
assumed elastic and isotropic, and the filler particles are modeled by round inclusions perfectly bonded to the polymer matrix.
The size distribution of the inclusions correspond to that of actual fillers. The destruction process of the components is
simulated by sequentially excluding the particles in which the maximum principal stress has achieved the ultimate value for
this component. A comparison of calculated and experimental characteristics of the polymer concrete showed errors of 2–4%
for the elastic modulus and about 10% for the ultimate strength if the finite-element cell included not less than 20–30 average-size
particles and 2–5 large ones.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 817–824, November–December, 2006 相似文献
3.
D. Pizele V. Kalkis R. Merijs Meri T. Ivanova J. Zicans 《Mechanics of Composite Materials》2008,44(2):191-196
Blends of low-density polyethylene (LDPE) and ethylene-octene copolymer (EOC) were obtained. The effect of EOC content and
absorbed radiation dose on the mechanical and thermomechanical properties of LDPE/EOC blends are investigated. Particular
attention is given to a tensile stress-strain analysis and the “form-memory” effect of the blends. With growing LDPE content,
the elastic modulus, the yield stress, and the thermorelaxation and residual stresses of the blends increase, but the ultimate
elongation at break decreases, which is caused by the higher crystallinity of polyethylene. As a result of radiation-induced
cross-linking, the elastic modulus, the yield stress (at a 1% strain), the ultimate yield strength, and the thermorelaxation
and residual stresses increase, while the ultimate elongation at break and the melt flow-behavior index decrease, which is
confirmed by the growing gel fraction in the blend.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 279–286, March–April, 2008. 相似文献
4.
Yu. A. Gorbatkina 《Mechanics of Composite Materials》2000,36(3):169-176
The relationship between the strength (σc) of unidirectional fiber-reinforced plastics in different stressed states and the interfacial strength of their components
is investigated. The shear adhesive strength (τ0) of fiber—matrix joints determined by the pull-out technique is used as a measure of the interfacial strength. To obtain
the correlation curves betweenσc andτ0, the experimental results are used, where both the plastic and adhesive strength change under the influence of a single factor.
In this case, such factors are the fiber surface treatment, nature and composition of polymer matrices, and test temperature.
It is shown that the strength of the glass, carbon, and boron plastics increases practically linearly with increased interfacial
strength. Such a behavior is observed in any loading conditions (tension, shear, bending, and compression). Sometimes, a small
(10–20%) increase in the adhesive strength induces a significant (50–70%) growth in the material strength. Therefore, the
interface is the “weak link” in these composites. The shape of theσc—τ0 curves for composites based on the high-strength and high-modulus aramid fibers and different thermoreactive matrices depends
on the nature of the fiber and the type of stress state. In many cases, the composite strength does not depend on the interfacial
strength. Then, the fiber itself is the “weak link” in these composites.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 291–304, May–June, 2000. 相似文献
5.
G. Bakradze J. Kajaks S. Reihmane R. Krutohvostov V. Bulmanis 《Mechanics of Composite Materials》2007,43(6):573-578
The effect of water on the mechanical properties (tensile modulus, ultimate tensile strength, tensile strain, and specific
work at break) of both chemically treated and untreated composites based on a recycled low-density polyethylene and linen
yarn production waste is analyzed. It is found that three water sorption-desorption cycles change the tensile properties of
both the materials irreversibly. This effect is considered as the result of partial fracture of the fiber-matrix interface.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 839–848, November–December, 2007. 相似文献
6.
R. D. Maksimov S. Gaidukovs M. Kalnins J. Zicans E. Plume 《Mechanics of Composite Materials》2006,42(1):45-54
The preparation of a polymer nanocomposite by compounding an aqueous polymer emulsion with an aqueous dispersion of montmorillonite
clay is described. A styrene-acrylate copolymer emulsion and a purified native montmorillonite clay from Latvian deposits
are used. An X-ray diffraction analysis and differential scanning calorimetric thermograms are shown. Data on the influence
of montmorillonite concentration on the tensile stress-strain diagram, elasticity, yield stress, breaking stress, and ultimate
elongation of the processed nanocomposite material are obtained.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 61–74, January–February, 2006. 相似文献
7.
The effect of the amount of absorbed water on the physicomechanical indices (tensile modulus, tensile strength, and ultimate strain) of composites based on secondary polyethylene (SPE) of two trademarks and linen yarn production waste (LW), both with and without a coupling agent (diphenylmetane diisocyanate - DIC), is evaluated. It is shown that the strength properties considerably depend on the time of water sorption and on the blend composition. The tensile strength decreases with increased amount of absorbed water (with increased time of exposure to distilled water) and with increased content of LW in the composites. This can be explained by the plasticizing effect of water molecules, which is confirmed by the increase in the ultimate strain of specimens after their exposure to water. The slight increase in the strength observed for the systems modified with DIC is probably caused by cross-linking of the free diisocyanate in the system under the action of moisture. The diisocyanate intensifies the interfacial interaction and retards the water-sorption process. Therefore, the resulting strength indices of these systems are higher than those of the unmodified compositions. 相似文献
8.
Adhesive ability of a heat-resistant double-chain polymer and the strength of CFRP based on it 总被引:1,自引:0,他引:1
Yu. A. Gorbatkina V. G. Ivanova-Mumjieva A. M. Kuperman I. I. Ponomarev V. I. Sidorenko 《Mechanics of Composite Materials》2008,44(4):371-378
The adhesive ability of a heat-resistant polyiminoquinazolindione (PIQD) binder, based on a double-chain polymer, and the
physicomechanical characteristics of unidirectional CFRPs made with it are investigated. It is shown that, at room temperature,
the strength of model adhesive joints (PIQD-steel wire) and of the CFRPs in shear and bending is rather low — about half of
that of similar specimens based on an epoxy binder. At the same time, all their mechanical characteristics, to a large measure
(50%), are retained at temperatures up to 450°C, which considerably exceeds the heat resistance of all polymer matrices used
at the present time. The elastic modulus of the CFRPs in bending practically remains the same up to 450°C.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 535–546, July–August, 2008. 相似文献
9.
A. K. Bledzki J. Zicans R. Merijs Meri D. Kardasz 《Mechanics of Composite Materials》2008,44(5):515-522
Blends of secondary rigid polyurethane foams (RPUFs) with soft polyurethane foams (SPUFs) were investigated. The effect of
SPUF content and its chemical nature on some physical and mechanical properties of the blends was evaluated. Owing to the
stronger intermolecular interaction and higher values of cohesion energy, the blends of RPUFs with polyester SPUFs showed
higher mechanical properties than those with polyether SPUFs. The density, hardness, ultimate strength, and the tensile, shear,
and flexural moduli increased, while the impact toughness, ultimate elongation, and damping characteristics decreased with
increasing RPUF content in the blends.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 737–746, September–October, 2008. 相似文献
10.
Fiber reinforced elastomeric matrix composites (EMCs) offer several potential advantages for construction of rotors for flywheel
energy storage systems. One potential advantage, for safety considerations, is the existence of maximum stresses near the
outside radius of thick circumferentially wound EMC disks, which could lead to a desirable self-arresting failure mode at
ultimate speeds. Certain unidirectionally reinforced EMCs, however, have been noted to creep readily under the influence of
stress transverse to the fibers. In this paper, stress redistribution in a spinning thick disk made of a circumferentially
filament wound EMC material on a small rigid hub has been analyzed with the assumption of total radial stress relaxation due
to radial creep. It is shown that, following complete relaxation, the circumferential strains and stresses are maximized at
the outside radius of the disk. Importantly, the radial tensile strains are three times greater than the circumferential strains
at any given radius. Therefore, a unidirectional EMC material system that can safely endure transverse tensile creep strains
of at least three times the elastic longitudinal strain capacity of the same material is likely to maintain the theoretically
safe failure mode despite complete radial stress relaxation.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 1, pp. 87–94, January–February, 2000. 相似文献
11.
A study has been made of the rheological and electrophysical properties (conductivity and dielectric loss angle) of aqueous solutions of polyvinyl alcohol (PVA), water-soluble carboxymethylcelluloses (Na-CMC), and compositions based on PVA and Na-CMC or methylcellulose, with PVA solution concentration 1% to 10% by weight and cellulose ether content in the polymer mixture up to 50% by weight. It was found that anisotropic structures can be formed in solutions based on PVA compositions under the influence of an orienting mechanical field; this is related to the formation of structure-sensitive associates in solution in the form of complexes.Paper presented at the 9th International Conference on the Mechanics of Composite Materials, Riga, October 1995.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 742–753, November–December, 1995. 相似文献
12.
The temperature dependence of the breaking stress and ultimate creep strain has been investigated in relation to preorientation, plasticization, and state of stress for polymethyl methacrylate, high-pressure polyethylene, polystyrene, and polyvinyl alcohol. The results of the mechanical tests are compared with the NMR data on the molecular mobility. The causes of the observed effects are discussed.Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 30–35, January–February, 1971. 相似文献
13.
The prediction of the high-cycle fatigue strength of polymeric and composite materials in asymmetric loading is considered.
The problem is solved on the basis of a nonlinear model of ultimate state allowing us to describe all typical forms of the
diagrams of ultimate stresses. The material constants of the model are determined from the results of fatigue tests in symmetric
reversed cycling, in a single fatigue test with the minimum stress equal to zero, and in a short-term strength test. The fatigue
strength characteristics of some polymers, glass-fiber laminates, glass-fiber-reinforced plastics, organic-fiber-reinforced
plastics, and wood laminates in asymmetric tension-compression, bending, and torsion have been calculated and approved experimentally.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 87–102, January–February, 2008. 相似文献
14.
Yu. S. Lipatov V. G. Matyushova V. F. Rosovitskii 《Mechanics of Composite Materials》1994,29(4):323-327
The viscoelastic properties of carbon fiber composites whose phenol-formaldehyde matrix is modified by thermodynamically incompatible isocyanate derivatives have been investigated. Data are given on fiber wetting (Table 11), internal stress (Table 2), viscoelastic properties (Fig. 1), and tensile strength (Fig. 2). The modified composites are strengthened by the addition of 0.5–4% oligomer additive. This process involves the formation of a two-phase structure, in which the additive phase microparticles act as a polymer filler. Due to selective interactions, the intermediate layer formed at the fiber-binder interface leads to changes in the viscoelastic properties and tensile strength of the matrix and improved maintenance characteristics for the material as a whole.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 440–445, July–August, 1993. 相似文献
15.
It has been found that when a uniaxial tension is applied to highly oriented polymer films of polypropylene, polyvinyl alcohol, or polyethylene, an increase in the intensity of the absorption bands corresponding to the vibrations of the C=O carbonyl groups is observed. These groups are produced by the oxidation of the free radicals formed on the rupture of the chemical bonds under the influence of mechanical stress. The composition of the products has been studied, and their concentration has been estimated. Curves giving the accumulation of C=O groups with time at constant load and with increase in stress for a fixed period of time under load have been studied. It is suggested that the rate of accumulation of C=O groups in both cases is determined chiefly by the rate of rupture of the molecular chains under load.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 433–436, May–June 1970. 相似文献
16.
The results of a study on the strength-deformation characteristics (tensile elastic modulus, ultimate strength, elongation
at break, and punching and tearing strengths) of two kinds of cellulose fiber nonwovens (CFNs) with dissimilar void content
and different geometrical parameters of cellulose fibers are discussed. The structural characteristics of composites prepared
by impregnation with poly(vinyl alcohol) water solutions are analyzed, too. Composites with volume fractions of polymer up
to 0.4% and volume fractions of voids up to 0.3% were prepared. Filling of voids by the polymer occurred without significant
changes in the structure of CFNs. The fraction of closed voids increased with polymer content. 相似文献
17.
V. E. Yudin J. U. Otaigbe S. I. Nazarenko W. D. Kim E. N. Korytkova 《Mechanics of Composite Materials》2011,47(3):335-342
Polyimide (PI) films based on poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PI-PM) were filled with different nanoparticles,
such as organically modified montmorillonite (MMT), vapor-grown carbon nanofibers (VGCF), and silicate nanotubes (SNT) of
different concentration.. Rheological measurements and structural investigations showed a relatively good dispersion of the
nanoparticles in the PI matrix to an extent that depended on the type and morphology of the nanoparticles used. The mechanical
(tensile modulus, strength, and deformation at break) and the barrier (oxygen permeability) properties of PI-PM nanocomposite
films were investigated. The polyimide nanocomposites filled with SNT and tubular VGCF nanoparticles showed an increased tensile
modulus with increasing volume concentration of the nanoparticles without a catastrophic decrease in the elongation at break.
In addition, the MMT particles, chemically modified with 4,4'-bis-(4′′-aminophenoxy)diphenylsulfone, significantly improved
the barrier properties of the PI-PM films, which exceeded those of the nanocomposites filled with VGCF or SNT. The relative
poor oxygen barrier and mechanical properties of the PI-PM/VGCF nanocomposite films are ascribed to the relative weak adhesion
between the VGCF and the polyimide matrix, which was confirmed by scanning electron microscopy of the fracture surface of
these films. 相似文献
18.
N. T. Smotrin 《Mechanics of Composite Materials》1965,1(3):54-57
Creep tests at constant stresses have been carried out on crystalline polyvinyl chloride (PVC) at 16, 40, and 60° to determine its limiting states (i.e., states defining its creep strength, complete cessation of creep strain, and the boundary of the range of invariance of the mechanical properties), which are shown to be described by exponential functions. An approximate method of determining creep is developed; in this method the creep strength is defined as the stress corresponding to the point of intersection of the limiting equilibrium curves and the stress/time-to-rupture curves.Mekhanika Polimerov, Vol. 1, No. 3, pp. 81–86, 1965 相似文献
19.
Yu. F. Leksashev 《Mechanics of Composite Materials》1965,1(5):13-15
The behavior of polyvinyl chloride sheet in torsion has been studied. Normal round test pieces were tested at strain rates of 0.3 and 1 rpm. The specimens were cut in the longitudinal and transverse directions of the sheet. The principal strength and plasticity characteristics of the material in torsion were obtained. During the tests torsion diagrams (Mt vs. ) were recorded. The specimens failed in shear. The shear modulus was determined on a special table device. The experiments showed that the shear modulus, limit of proportionality, and tensile strength have the same values in both longitudinal and transverse directions. The values of the angle of twist at failure are large and vary over a wide range.Mekhanika Polimerov, Vol. 1, No. 5, pp. 19–24, 1965 相似文献
20.
We deal with the thermomechanical response of multilayer satin weave carbon-fiber-reinforced polymer (CFRP) laminates with
internal and/or edge cracks and temperature-dependent material properties subjected to tensile loading at cryogenic temperatures.
The composite material is assumed to be under the generalized plane strain. Cracks are located in the transverse fiber bundles
and extend to the interfaces between two fiber bundles. A finite-element model is employed to study the influence of residual
thermal stresses on the mechanical behavior of multilayer CFRP woven laminates with cracks. Numerical calculations are carried
out, and Young’s modulus and stress distributions near the crack tip are shown graphically.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 479–492, July–August, 2008. 相似文献