共查询到20条相似文献,搜索用时 350 毫秒
1.
I. J. Gnip S. I. Vaitkus V. I. Kersulis S. A. Veyelis 《Mechanics of Composite Materials》2007,43(5):433-444
The results obtained in an experimental investigation of deformability of expanded polystyrene (EPS) under short-term compression
are presented. The density of EPS varied from 13 to 28 kg/m3. The method of design of experiments was used to determine the elastic modulus and the ultimate strain (corresponding to
the end of quasi-linear deformability) under compression stresses operating perpendicularly and parallel to the faces of EPS
products. A graphical interpretation of the models is also presented. Based on the experimental data obtained, it was concluded
that the expanded polystyrene was homogeneous in mutually perpendicular planes with respect to its deformability in compression.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 639–656, September–October, 2007. 相似文献
2.
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
3.
Results of an experimental investigation into the mechanical properties of concrete cylinders confined by a carbon-epoxy composite
wrapping are presented. It is shown that, for all the con fined con crete spec i mens tested, the loading paths in the normalized
stress space follow a single master curve, what ever the concrete strength and confinement intensity. At stresses in the confined
concrete exceeding the strength of plain concrete, the tangent modulus was found to depend on the slope angle of the master
curve and the asymptotic value of the differential Poisson ratio (the first derivative of the lateral strain with respect
to the axial one). Formulas for predicting the ultimate axial strain and the tangent modulus are derived and compared with
the corresponding fib (fédération internationale du béton) recommendations.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 433–448, July–Au gust, 2006. 相似文献
4.
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
5.
The external confinement by CFRP wrappings is a very efficient method to increase the load-carrying capacity of round concrete
columns. Nevertheless, the serviceability of such columns under loads exceeding the strength of unconfined concrete is limited
by different factors. One of them is the reduced stability of the columns due to the significantly reduced tangent elastic
modulus inactive loading. To increase the critical load of buckling instability of concrete columns, an additional longitudinal
composite reinforcement can be used. In this paper, the stability and strength of concrete columns confined by circumferential
wrappings and strengthened with a longitudinal external CFRP reinforcement are studied. Plain and confined columns of length
300 and 1500 mm were tested. Theoretical predictions show that the additional longitudinal reinforcement is efficient in improving
the stability of confined columns in the region of moderate slenderness. The prediction for the ultimate strength and stability
of the columns coincides rather well with experimental results.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 295–308, May–June, 2005. 相似文献
6.
The strength and fracture mechanism of the contact zone between a carbon-fiber-reinforced plastic (CFRP) and concrete in flexural
structural elements is investigated. Two methods for calculating the shear force in the contact zone are considered, one of
which takes into account the compliance of the zone and gives results agreeing rather well with experimental data for beams,
regardless of the way the CFRP is fastened to concrete. The method of shear stresses is good for beams with in significant
shear strains between CFRP and concrete. A method allowing for hardening of the contact zone is suggested. It is shown that
the fracture mechanism of the zone depends on the way of fastening the CFRP and the depth the adhesive penetrates into concrete.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 687–700, September–October, 2007. 相似文献
7.
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
8.
G. Teters 《Mechanics of Composite Materials》2007,43(1):59-62
The multicriteria optimization of the structure and geometry of a laminated anisotropic composite plate subjected to thermal
and shear loading is considered. From the known properties of the monolayer and given values of variable structural parameters,
the thermoelastic properties of the layered composite are determined. The optimization criteria — the critical shear load
and the longitudinal thermal stresses — depend on two variable design parameters of composite properties and temperature.
In the space of optimization criteria, the domain of allowable solutions and the Pareto-optimal subregion are found.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 85–92, January–February, 2007. 相似文献
9.
Effects of temperature and moisture on the mechanical properties of polyester resin in tension 总被引:1,自引:0,他引:1
The effect of environment on the physical and mechanical properties of composite materials in some cases is determined by
the environmental sensitivity of the binder. The results of experimental investigation of the deformability and strength of
polyester resin, widely used as a binder in composites, upon the action of stationary and quasi-stationary loads, temperatures,
and moisture are presented. The ranges of acceptable values of these services factors are determined. The elastic modulus
and tensile strength of the material are obtained from quasi-static tests. The viscoelastic behavior of the resin is investigated
in creep tests. From the results of a short-term experiment with stepwise loading up to failure, it is found that the creep
of specimens with a moisture content of 0.14% can be described by a linear viscoelastic model for stresses up to 20 MPa (two
thirds of the strength). The action of single loading impulses is summarized according to the Boltzmann superposition principle.
The temperature and absorbed moisture are considered as factors accelerating the relaxation processes in the material. The
creep activation under the action of these factors is described using the methods of time-temperature and time-moisture equivalence.
The results of short-term creep tests allow us to determine the relaxation characteristics of the material in stationary conditions.
The long-term creep under close-to-service conditions is predicted using these data and quite good agreement with the control
test is obtained. The sensitivity of the material characteristics (strength, elastic modulus, and creep strain) to the action
of temperature and moisture is estimated. The creep strain is most sensitive to the action of environmental factors. For a
fully saturated material (moisture content 1.64 wt.%), after one hour creep, this strain four times exceeds that of a dry
one. The same growth in deformability is caused by an 18°C increase in temperature. A quantitative comparison of the characteristics
of polyester and epoxy resins allows us to choose the binder for composites and to estimate the expected environmental effect.
Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 395–406, May–June, 2000. 相似文献
10.
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.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 279–286, March–April, 2008. 相似文献
11.
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
12.
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
13.
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
14.
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
15.
The transient creep of a UD composite with a quadratic arrangement of elastic fibers of quadratic cross section is investigated.
The deformational properties of the composite are determined from the known properties of its constituents. A structural model
of the UD composite is developed, whose minimal elementary cell contains four elements. The stress-strain state of the elements
is assumed homogeneous. Two types of basic and resolving governing equations of transient creep are deduced, which are based
on static or kinematic assumptions. In each of the cases, a formula for the longitudinal elastic shear modulus of the composite
is found. The stationary solutions of creep equations allow one to obtain formulas of the steady-state creep of the composite
in a form similar to Norton’s law. Numerical calculations are also performed, and a comparison of the results with data given
in the literature bears witness to the efficiency of the models developed and the solutions obtained.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 437–448, July–August, 2007. 相似文献
16.
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
17.
A. Naceri 《Mechanics of Composite Materials》2007,43(5):403-408
An analysis of the mechanical and acoustic responses of a laminate composed of 12 layers of glass fiber fabric/epoxy resin
and conditioned in environments with relative humidities of 0, 60, and 96% RH at 60°C is presented. The first part of the
study consists in following the weight gain according to the duration of hygrothermal conditioning, and the second part—in
test ing 45°-oriented specimens in uniaxial tension up to failure at constant imposed displacement rates, with registrating
the acoustic emission to track the damage process. The influence of moisture content in the material showed up as a significant
decrease in its shear modulus, shear stress, and acoustic emission with growing quantity of absorbed water. An exponential
function is proposed for describing the relationship between the varying shear modulus and the shear strain.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 595–602, September–October, 2007. 相似文献
18.
This paper deals with the shear strengthening of Reinforced Concrete (RC) flexural members with externally bonded Fiber-Reinforced
Polymers (FRPs). The interaction between an external FRP and an internal transverse steel reinforcement is not considered
in actual code recommendations, but it strongly influences the efficiency of the shear strengthening rehabilitation technique
and, as a consequence, the computation of interacting contributions to the nominal shear strength of beams. This circumstance
is also discussed on the basis of the results of an experimental investigation of rectangular RC beams strengthened in shear
with “U-jacketed” carbon FRP sheets. Based on experimental results of the present and other investigations, a new analytical
model for describing the shear capacity of RC beams strengthened according to the most common schemes (side-bonded and “U-jacketed”),
taking into account the interaction between steel and FRP shear strength contributions, is proposed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 339–356, May–June, 2008. 相似文献
19.
Results of an experimental and theoretical investigation of composite beams as elements of bridge superstructure are presented.
Experiments on beams of two types — made of wood and the same beams with a composite sheath — were carried out. The rigidity
of the beams of the second type was about twice as high as that of the first ones. The classical bending model of composite
beams gave deflections smaller than experimental ones. To reconcile these results, the model is refined by including the effect
of shear. The deflections are represented as classical ones multiplied by a shear factor which depends on the bending and
shear stiffnesses and the span length of the beams. As a result, a good agreement between calculations and experiments is
achieved.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 449–462, July–August, 2006. 相似文献
20.
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.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 535–546, July–August, 2008. 相似文献