共查询到20条相似文献,搜索用时 31 毫秒
1.
G. G. Bakradze J. A. Kajaks S. A. Reihmane J. E. Lejnieks 《Mechanics of Composite Materials》2007,43(5):427-432
The effect of the amount of sorbed water on the mechanical properties (tensile modulus, tensile strength, unit work of fracture,
and characteristic strains) of composites based on a recycled low-density polyethylene, both unmodified and modified with
diphenylmethane diisocyanate (DIC), is an a lyzed by statistical methods. The results of tensile tests are found to depend
on the amount of sorbed water considerably. The elastic modulus, the unit work of fracture, and the characteristic strains
correlate linearly with the amount of water. It is found that the elastic modulus drops after the sorption of water, but then,
during the desorption process, it is restored gradually and reaches its initial value after a 30-day drying. This is explained
by the plasticizing effect of water on composite materials containing hydrophilic natural fibers. DIC improves the interfacial
interaction of the fiber-matrix interface and slows down the desorption of water. The investigations of the main deformational
and strength characteristics of the unmodified and modified systems showed that the ad verse effect of water completely disappeared
after a 30-day drying. The same conclusion, with a 95% probability, can be drawn from the results of an analysis of variance
(ANOVA).
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 626–638, September–October, 2007. 相似文献
2.
R. D. Maksimov S. Gaidukovs J. Zicans M. Kalnins E. Plume V. Spacek P. Sviglerova 《Mechanics of Composite Materials》2006,42(3):263-272
The preparation of polymer nanocomposites by mixing a solution of a styrene-acrylate copolymer with a suspension of organically
modified montmorillonite in dimethyl formamide is described. Seven different compositions with organomontmorillonite content
from 0 to 7 wt.% were prepared and tested. Results of their X-ray diffraction analysis are presented. Data on the influence
of organomontmorillonite content on the tensile stress-strain curves, elastic modulus, strength, and ultimate elongation of
the nanocomposites are obtained. The concentration dependences of elastic properties of materials with differently oriented
platelike nanoparticles is analyzed by using an algorithm elaborated for stepwise calculations of elastic constants with account
of the features of structural hierarchy of intercalated and exfoliated nanocomposites.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 375–388, May–June, 2006. 相似文献
3.
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
4.
A variant of determining the elastic characteristics of composites containing irregularly oriented shape-anisotropic filler
particles of two types (short fibers and thin platelets) is considered. The effective elastic constants of the composites
are calculated by using the method of orientational averaging of elastic characteristics of isolated transversely isotropic
structural elements reinforced with unidirectionally oriented short fibers or coplanarly arranged thin platelets. The superposition
of elastic properties of the irregularly oriented structural elements, with account of their orientational distribution in
the composite material, is accepted. The calculation results are compared with experimental data for the effective elastic
moduli of polymeric composites reinforced with short glass fibers and of polymeric nanocomposites containing the platelet-type
particles of organically modified montmorillonite.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 285–300, May–June, 2006. 相似文献
5.
The relationship between the tensile strength and deformation characteristics, composition, and structural organization of
films obtained by casting of two-component water-based system blends — a solution of the rigid partly crystalline polymer
polyvinyl alcohol (PVA) and an emulsion of the compliant amorphous polymer polyvinyl acetate (PVAc) — has been investigated.
The aim of this investigation was to ascertain the possibility of obtaining film materials with increased deformability based
on the biodegradable PVA. The composition dependences of the initial modulus of elasticity, the maximum stress, yield stress,
the ultimate strength, the ultimate strain, and of the unit work of fracture and other characteristics of films have been
analyzed. An analysis of the tensile true stress–strain curves of systems with volume fractions of PVA less than 0.5 points
to their considerable orientation strengthening upon tension. 相似文献
6.
N. Lilichenko R. D. Maksimov J. Zicans R. Merijs Meri E. Plume 《Mechanics of Composite Materials》2008,44(1):45-56
The preparation of an environmentally friendly nanocomposite based on plasticized potato starch and unmodified montmorillonite
clay is described. Data on the influence of montmorillonite concentration on the mechanical properties of the materials obtained
are reported. The effective elastic constants of the nanocomposites are calculated. The calculation results are compared with
experimental data. The influence of montmorillonite content on the moisture permeability is also investigated.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 61–76, January–February, 2008. 相似文献
7.
The mechanical properties of unidirectional GFRPs based on an ED-22 epoxy resin were investigated. The resin was modified
with a PSK-1 polysulphone or a PEF-3a epoxyurethane oligomer. Triethanolaminotitanate or diaminodiphenilsulphone was used
as a hardener. The modification did not improve the mechanical properties of GFRPs in quasi-static loading; but in a low-speed
impact loading, the shear strength of epoxypolysulphone GFRPs with 20 wt.% PSK-1 increased by 20–25%. For all the GFRPs investigated,
the shear strength grew linearly with the logarithm of loading rate. The introduction of the modifiers increased the fracture
toughness considerably: by 100 and 70% for GFRPs modified with 20 wt.% PSK-1 and 50 wt.% PEF-3a, respectively.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp.739–758, November–December, 2006. 相似文献
8.
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.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 817–824, November–December, 2006 相似文献
9.
Zhang Shu-hui Liang Guo-zheng Zhang Wei Zeng Jin-fang 《Mechanics of Composite Materials》2006,42(6):507-512
The surface of aramid fibers was modified with a polymer coating — a surface treatment reagent containing epoxy resin. The
resulting fibers were examined by using NOL tests, hydroburst tests, and the scanning electron microscopy. The modified fibers
had a rougher surface than the untreated ones. The interlaminar shear strength of an aramid-fiber-reinforced epoxy composite
was highest when the concentration of polymer coating system was 5%. The translation of fiber strength in an aramid/epoxy
composite vessel was improved by 8%. The mechanism of the surface treatment of fibers in improving the mechanical properties
of aramid/epoxy composites is discussed.
Russian translation publeshed in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 729–738, November–December, 2006. 相似文献
10.
N. M. Barkoula A. Paipetis T. Matikas A. Vavouliotis P. Karapappas V. Kostopoulos 《Mechanics of Composite Materials》2009,45(1):21-32
The environmental durability of carbon nanotube (CNT)-modified carbon-fibre-reinforced polymers (CFRPs) is investigated. The
key problem of these new-generation composites is the modification of their polymer matrix with nanoscaled fillers. It was
recently demonstrated that the damage tolerance of these materials, as manifested by their fracture toughness, impact properties,
and fatigue life, can be improved by adding CNTs at weight fractions as low as 0.5%. This improvement is mainly attributed
to the incorporation of an additional interfacial area between the CNTs and the matrix, which is active at the nanoscale.
However, this additional interface could have a negative effect on the environmental durability of the aforementioned systems,
since it is well known that the moisture absorption ability of a matrix is enhanced by the presence of multiple interfaces,
which serve as an ingress route to water. To examine this problem, CNT-modified CFRPs were exposed to hydrothermal loadings.
At specified intervals, the composites were weighted, and the water uptake vs. time was recorded for both the modified and
a reference systems. The electrical conductivity of the composites was registered at the same time intervals. After the environmental
exposure, the interlaminar shear properties of the conditioned composite systems were measured and compared with those of
unmodified composites, as well as with the shear properties of unexposed laminates.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 31–48, January–February, 2009. 相似文献
11.
The influence of mixing process (in a two-roll mill, high-speed mixer, or twin-screw extruder) on the strength properties
of polypropylene/wood fiber composites was studied. The best results were obtained for composites compounded in a twin-screw
extruder. The water uptake and the influence of moisture on the flexural strength (σfl) and modulus (Efl) were studied by immersion of the composites in water at 20, 50, and 90°C. Most strongly the moisture affected the value
of Efl, but the degree of water uptake and the change in σfl and Efl also depended on temperature and the presence of a modificator—maleated polypropylene (MAH). MAH improved the strength properties
of the composites both in dry and wet states and also decreased the extent of water uptake and swelling in cyclic (soaking/drying)
tests.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 101–114, January–February, 2006. 相似文献
12.
Yu. Paramonov J. Andersons M. Kleinhofs A. Paramonova 《Mechanics of Composite Materials》2008,44(4):389-396
The possibility of using a unified mathematical model, based on the theory of Markov chains, to describe the distribution
of the conditional fatigue limit at a fixed number of loading cycles and the residual strength of a specimen after cyclic
loading is demonstrated. Numerical examples are presented.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 559–568, July–August, 2008. 相似文献
13.
T. Fiedler B. Sturm A. Öchsner J. Gracio G. Kühn 《Mechanics of Composite Materials》2006,42(6):559-570
The mechanical properties of periodic hollow-sphere structures are investigated numerically. Young’s modulus and the Poisson
ratio are determined in order to describe their linearly elastic behaviour. The initial compressive yield strength is also
calculated. The spheres are located at the nodes of a cubic primitive lattice. The cohesion is achieved by an adhesive concentrated
in the minimum gap between neighbouring spheres. The geometry of the structure is discretized based on regular hexahedral
elements. This approach is much more time-consuming, but it is important in order to achieve a more accurate simulation of
the nonlinear behaviour (e.g., plasticity) of such materials.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 803–816, November–December, 2006. 相似文献
14.
R. D. Maksimov S. Gaidukovs J. Zicans M. Kalnins E. Plume V. Spacek P. Sviglerova 《Mechanics of Composite Materials》2006,42(4):353-362
The results of an investigation into the barrier and thermal properties of polymer nanocomposites prepared by blending a styrene-acrylate
copolymer solution with a suspension of organically modified montmorillonite are presented. The influence of organomontmorillonite
content on the barrier properties of the nanocomposite is investigated with the example of water vapor permeability. The experimental
values of the permeability coefficient are compared with those calculated by using a model taking into account the increased
path of diffusing water molecules caused by the shielding effect of plate like particles. The thermograms of differential
scanning calorimetry in the temperature range from −40 to 130°C are presented. The results of a thermogravimetric analysis
for specimens heated in air to 800°C are also reported.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 503–516, July–August, 2006. 相似文献
15.
A method for determining the stiffness and rheological characteristics of composite materials, based on minimizing the mismatch
of experimental data and the results of numerically modeling nonstationary deformation processes in shells ofrevolution made
of composites materials, is presented. This approach is used for analyzing the damping characteristics of chaotically reinforced
and cloth-reinforced composites.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 449–464, July–August, 2007. 相似文献
16.
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.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 87–102, January–February, 2008. 相似文献
17.
An attempt is made to find a solution by which the effect of neighboring filler particles on the strength of composites could
be indirectly estimated. The stresses in composites with a great amount of filler are calculated. Composites based on epoxy-resin
binder are tested. A comparison of different models shows that the modified Kerner model reflects only the tendency for the
compression strength to change with the degree of filling. The relations between the compression strength and the degree of
filling are better described by models allowing for constraint of the plastic deformations of the matrix. However, in this
case, the effect of the neighboring particles is not properly taken into account.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 575–584, September–October, 1999. 相似文献
18.
This paper presents a new approach based on extrapolation to accelerate the linear convergence process of Vectorized Moore–Skelboe (VMS) algorithm. The VMS is a modified version of basic Moore–Skelboe (MS)
algorithm, where the vectorization is used as a means to speed up the basic MS algorithm. We propose to further accelerate
the converging process of VMS from linear to quadratic by combining the Richardson extrapolation technique with VMS. The effectiveness of the proposed algorithm is tested on various
multivariate examples and compared with the unaccelerated conventional method, i.e., MS and well-known optimization software
GlobSol. The test results show that the proposed extrapolation-based VMS offer considerable speed improvements over both the
existing algorithms. 相似文献
19.
The purpose of this note is to generalize the roof duality theory of Hammer, Hansen and Simeone to the case of polynomial
0–1 optimization (0-1PP). By reformulating 0-1PP and expanding some of their definitions, we show that most of the results
for quadratic 0–1 problem (0-1QP) can be extended to the general polynomial case. 相似文献
20.
Based on the weakest-link model, a family of fiber strength distributions is investigated assuming a two-stage failure process.
At the first stage, a weakest link is formed (instantly or gradually), but at the second one the fracture of this link takes
place. The gradual accumulation of flaws is described with the aid of Markov chain theory. The adequacy of the models considered
is verified by checking them against experimental strength data for E-glass and flax fibers of various lengths. It is found
that the models are not less accurate, but are even better, in a number of cases, than the model based on the known modified
Weibull model with a power-law relation between the fiber length and the scale parameter.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 179–192, March–April, 2006. 相似文献