共查询到20条相似文献,搜索用时 31 毫秒
1.
Results of an experimental investigation into the thermal behavior and mechanical properties of a room-temperature-cured epoxy
adhesive (diglycidyl ether of bisphenol A, DGEBA) cross-linked with polyetheramines and filled with different fillers, namely
nanosilica, liquid rubber (CTBN), and clay, are reported. The nanosilica and liquid rubber increased the flexural strength
and elastic modulus of the adhesive systems; the addition of clay particles raised the elastic modulus significantly, but
embrittled the adhesive. Establishing a correct cure time is very important for bonded-in timber structures, as it will affect
the bond strength. A study on the effect of cure time on the flexural strength was carried out, from which it follows that
the adhesives should be cured for at least 20 days at room temperature. The damping characteristics and the glass-transition
temperature of the adhesives were determined by using a dynamic mechanical thermal analysis. The results showed that the filled
adhesives had a higher storage modulus, which was in agreement with the elastic moduli determined from static bending tests.
The introduction of the fillers increased its glass-transition temperature considerably.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 599–614, September–October, 2006. 相似文献
2.
C. Gonilho Pereira R. Fangueiro S. Jalali M. Araujo P. Marques 《Mechanics of Composite Materials》2008,44(3):221-230
This paper reports on the development of braided reinforced composite rods as a substitute for the steel reinforcement in
concrete. The research work aims at understanding the mechanical behaviour of core-reinforced braided fabrics and braided
reinforced composite rods, namely concerning the influence of the braiding angle, the type of core reinforcement fibre, and
preloading and postloading conditions. The core-reinforced braided fabrics were made from polyester fibres for producing braided
structures, and E-glass, carbon, HT polyethylene, and sisal fibres were used for the core reinforcement. The braided reinforced
composite rods were obtained by impregnating the core-reinforced braided fabric with a vinyl ester resin. The preloading of
the core-reinforced braided fabrics and the postloading of the braided reinforced composite rods were performed in three and
two stages, respectively. The results of tensile tests carried out on different samples of core-reinforced braided fabrics
are presented and discussed. The tensile and bending properties of the braided reinforced composite rods have been evaluated,
and the results obtained are presented, discussed, and compared with those of conventional materials, such as steel.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 327–338, May–June, 2008. 相似文献
3.
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).
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 626–638, September–October, 2007. 相似文献
4.
Glasfibre structures feature high potentials for optimization and substitution of conventional materials like steel and aluminum and their alloys. The paper deals with the insertion of glasfibre trusses into thin glasfibre structures to reinforce them. The effective material properties of the glasfibre structures were estimated by experiments and simulations. Furthermore the Young's modulus of the trusses was obtained by bending tests and tension tests. A comparison between bending experiments and bending simulations is given. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
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
6.
Sodium fluorohectorite (FH) was incorporated into polystyrene (PS) in amounts of 4.5 and 7 wt.% by melt mixing, with and without
latex precompounding. The latex precompounding was used for the latex-mediated predispersion of FH particles. The related
masterbatch was produced by mixing PS latex with the water-swellable FH, followed by drying. The dispersion of FH in PS was
studied by transmission-, scanning electron-, and atomic force microscopy techniques (TEM, SEM, and AFM, respectively). The
stress relaxation in the PS composites was determined in short-term isothermal tests. The latter were performed at various
temperatures between 25 and 75°C. The direct melt mixing of FH with PS resulted in microcomposites, whereas the masterbatch
technique gave rise to nanocomposites. The master curves (relaxation modulus vs. time), constructed by applying the time-temperature
superposition principle (TTSP), showed that the Williams-Landel-Ferry (WLF) equation, the Maxwell model, and the Findley power
law were fairly applicable to the experimental results obtained.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 709–722, September–October, 2008. 相似文献
7.
The outstanding improvement in the physical properties of cyanate esters (CEs) compared with those of competitor resins, such
as epoxies, has attracted appreciable attention recently. Cyanate esters undergo thermal polycyclotrimerization to give polycyanurates
(PCNs). However, like most thermo setting resins, the main draw back of CEs is brittleness. To over come this disadvan tage,
CEs can be toughened by the introduction of polytetramethylene glycol (PTMG), a hydroxyl-terminated polyether. How ever, PTMG
has a detrimental impact on Young’s modulus. To simultaneously enhance both the ductility and the stiffness of CE, we added
PTMG and an organoclay (mont morillonite, MMT) to it. A series of PCN/PTMG/MMT nanocomposites with a constant PTMG weight
ratio was pre pared, and the resulting nanophase morphology, i.e., the degree of filler dispersion and distribution in the
composite and the thermomechanical properties, in terms of glass-transition behaviour, Young’s modulus, tensile strength,
and elongation at break, were examined using the scanning elec tron micros copy (SEM), a dynamic mechanical analysis (DMA),
and stress–strain measurements, re spectively. It was found that, at a content of MMT below 2 wt.%, MMT nanoparticles were
distributed uniformly in the matrix, suggesting a lower degree of agglomeration for these materials. In the glassy state,
the significant increase in the storage modulus revealed a great stiffening effect of MMT due to its high Young’s modulus.
The modification with PTMG led to a 233% greater elongation at break compared with that of neat PCN. The nanocomposites exhibited
an invariably higher Young’s modulus than PCN/PTMG for all the volume factors of organoclay examined, with the 2 wt.% material
displaying the most pronounced in crease in the modulus, in agreement with micros copy results.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 255–268, March–April, 2009. 相似文献
8.
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
9.
V. V. Zuev 《Mechanics of Composite Materials》2012,47(6):603-608
The effect of C60 fullerene on the mechanical properties of epoxy resins has been investigated. It is found that this filler affects the tensile
modulus and tensile strength of epoxy compositions only slightly, but their impact strength at a 0.01–0.12 wt.% content of
C60 increases by about 100–200%. A molecular mechanism of the toughening effect of C60 on epoxy resins is suggested. 相似文献
10.
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.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 375–388, May–June, 2006. 相似文献
11.
An epoxy resin (Epon 828) was filled with single- and multiwalled carbon nanotubes (SWCNT and MWCNT) in two steps by using
the high shear mixing and ultrasonication techniques. The melt flow of the composites was characterized in a plate/plate rheometer.
The thermomechanical properties of the composites were determined in dynamic mechanical analysis tests performed at various
frequencies and temperatures. It was found that the incorporation of SWCNT or MWCNT increased the viscosity and stiffness
of epoxy above its glass-transition temperature. The time-temperature superposition principle was employed to estimate the
storage modulus of the composites as a function of frequency (f = 10–33–103 Hz) in the form of master curves. 相似文献
12.
The paper deals with evaluation of the bond performance between a CFRP plate and concrete with respect to various compressive
strengths of concrete and bond lengths of the CFRP plate as parameters. To consider stress conditions in the tensile zone
of reinforced concrete (RC) structures, double-lap axial tension tests were conducted for eight specimens with CFRP plates
bonded to concrete prisms. In addition, a simple linear bond-slip model for the CFRP plate/concrete joints, developed from
the bond tests, was used. To verify the model proposed, a total of seven RC beams were strengthened with CFRP plates and tested
in flexure employing various bond lengths, strengthening methods, and numbers of CFRP plates. A nonlinear finite-element analysis,
with the bond–slip model incorporated in the DIANA program, was performed for the strengthened RC beams. Also, the results
of flexural test and analytical predictions are found to be in close agreement in terms of yield and ultimate loads and ductility. 相似文献
13.
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
14.
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
15.
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
16.
The mixed-mode I + II interlaminar fracture of multidirectional glass/epoxy laminates is investigated. Mixed-mode bending
(MMB) tests were performed on specimens with delaminations in 0/θ-type interfaces, with θ varying from 0 to 90°. Preliminary
three-dimensional finite-element analyses validated the beam theory model (BTM) used for analysing experimental data. The
compliances measured are in a good agreement with BTM predictions. The total critical energy release rate Gc varies linearly with the mode II ratio GII/G, although some discrepancies are observed in the high-mode II results for the 0/45 and 0/90 specimens.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 349–366, May–June, 2007. 相似文献
17.
The plasticity theory has been successfully used for describing the nonlinear deformation of laminated composite materials
under a monotonically increasing loading. Generally, several tests are needed to determine the parameters of the plastic potential
for a laminate. We explore an alternative approach and obtain the plastic potential by using theoretical considerations based
on a laminate analysis. The model is shown to provide an accurate prediction for the response of a cross-ply glass/epoxy laminate
under uniaxial tensile loading at different angles to the material orthotropy axes.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 309–318, May–June, 2007. 相似文献
18.
A way of determining the flexibility of wood-pulp fibres is developed, which involves i) a precise measurement of the topology
of single-fibres by using a confocal laser scanning microscope and ii) the measurement of the elastic modulus of the fibres
by using a single-fibre fatigue cell. Reported in this paper are the initial results of tests carried out on black spruce
fibres, which have been subjected to three different levels of mechanical refining energy, namely ∼1100, 2300, and 3500 kWh/t.
It is found that the fibre flexibility rises significantly between the first and second energy levels, but it does not change
to the same degree between the second and third ones. The described procedure of measuring the flexibility of fibres may be
used to establish the appropriate refiner energy necessary for the production of a specific grade of paper.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 115–128, January–February, 2006. 相似文献
19.
The transient response of sandwich beams, plates, and shells with viscoelastic layers under impulse loading is studied using
the finite element method. The viscoelastic material behavior is represented by a complex modulus model. An efficient method
using the fast Fourier transform is proposed. This method is based on the trigonometric representation of the input signals
and the matrix of the transfer functions. The present approach makes it possible to preserve exactly the frequency dependence
of the storage and loss moduli of viscoelastic materials. The logarithmic decrements are determined using the steady state
vibrations of sandwich structures to characterize their damping properties. Test problems and numerical examples are given
to demonstrate the validity and application of the approach suggested in this paper.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 367–378, March–April, 2000. 相似文献
20.
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