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1.
The fatigue failure of reinforced plastics and unoriented polymers under a joint action of static and high-cycle loadings is considered. The fatigue failure strength is estimated from stress range diagrams with a static tensile component. The models of ultimate state are constructed based on the hypothesis of existence of a unified ultimate diagram invariant with respect to the number of cycles to failure. The unified diagram is given by a transcendental power function whose exponent characterizes the sensitivity of the material to the stress-cycle asymmetry. The models of ultimate state make it possible to span practically all forms of ultimate diagrams of composite and polymer materials, including concave, rectilinear, S-shaped, and convex ones. 相似文献
2.
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
3.
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates
containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function
allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the
theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy
of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups;
in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress
criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 531–570, July–August, 2007. 相似文献
4.
Degradation of the residual strength of a glass-fiber-reinforced polyester composite of a lay-up typical of the wind rotor
blade material is studied at low-cycle fatigue. A gradual reduction of the residual strength is observed as expected for GRP,
accompanied by an increasing scatter of strength. The residual strength model based on the strength-life equal rank assumption
yields an accurate approximation of experimental data. The strength reduction at a stress level corresponding to high-cycle
fatigue (N>10
6 cycles) appears to correlate well with the test results at higher stress levels, which indicates that the strength degradation
at the design stress level can be evaluated using low-cycle tests. Assuming that the parameters of the strength degradation
model do not depend on the applied stress level, the residual strength data obtained in low stress level tests of comparatively
short duration can be used to estimate the average fatigue life at the same stress thus reducing the total test time.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 595–604, September–October, 1999. 相似文献
5.
Within the framework of a unified mathematical model based on the Markov chain theory, an attempt is made to describe the
distribution of static strength, the fatigue curve, and the accumulation of fatigue damages. It is assumed that the fatigue
failure of a test specimen occurs after the destruction of some its critical microvolume consisting of two — elastic (brittle
fibers) and plastic (matrix) — parts. In the second part, plastic strains accumulate as soon as the cyclic load exceeds some
level. Numerical examples are presented.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 615–630, September–October, 2006. 相似文献
6.
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
7.
I. J. Gnip S. A. Veyelis V. I. Kersulis S. I. Vaitkus 《Mechanics of Composite Materials》2007,43(1):85-94
Data obtained in investigating the ultimate strength and deformability of expanded polystyrene under short-term shear loading
according to EN 12090 are discussed. Linear regression equations are used for describing the ultimate shear strength and modulus
in relation to the density of EPS. A correlation is found to exist between the ultimate strength of EPS and its density and
specimen thickness. An empirical dependence between the shear modulus and density of EPS is established. The strains corresponding
to the conditional limit of proportionality and to the ultimate shear strength of EPS in short-term loading are determined.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 121–134, January–February, 2007. 相似文献
8.
简支矩形复合材料薄板压缩屈曲后的极限强度 总被引:2,自引:0,他引:2
本文通过283块简支矩形玻璃钢薄板的压缩屈曲后极限强度的试验,证明了复合材料薄板在屈曲失稳后仍能继续承载,以玻璃钢为例,可以超过临界载荷的十几倍。文中对薄板的极限强度进行了大挠度和小挠度理论分析,结合复合材料的能量强度理论,最后得出有关极限强度计算公式的C参数曲线,对于45°方向的薄板与试验结果较符合,对于经纬向薄板当β<0.11时比试验结果略大。文中给出的C参数可供产品设计时参考。 相似文献
9.
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
10.
The elastic deformation behavior and the load-carrying capacity of unidirectional carbon fiber laminates under static loading
at room and cryogenic (down to 77 K) temperatures are investigated. The possible ways of predicting their elastic and strength
characteristics proceeding from the volume content and mechanical parameters of fibers and matrix are analyzed.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 583–598, September–October, 2006. 相似文献
11.
For strengthening bent beams, plates of reinforced plastics are glued to their tensioned surface. As s result, the beam becomes
layered, and it is possible to control its rigidity and deflection. Based on the methods of structural mechanics of layered
media, a method is elaborated for determining the deflection of such beams on the entire range of loading up to their ultimate
failure. A comparison between the theoretical and experimental results is carried out.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 45–60, 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.
Behavior of concrete cylinders confined by carbon-composite tapes and prestressed yarns 1. Experimental data 总被引:1,自引:0,他引:1
V. Tamuzs R. Tepfers Chi-Sang You T. Rousakis I. Repelis V. Skruls U. Vilks 《Mechanics of Composite Materials》2006,42(1):13-32
The results of a comprehensive test program for the mechanical behavior of round concrete specimens confined by carbon-fiber
epoxy tapes and prestressed carbon yarns are reported. Five different concrete batches of compressive strength from 20 to
100 MPa and the confinement of various thickness and pretension level were investigated. The specimens, which were subjected
to monotonic or repeated compressive loadings, showed a nonlinear stress-strain behavior with a significant ductility and
increased ultimate strength, in contrary to the brittle behavior of plain concrete. The limit of linearity on the stress-strain
diagrams of the confined concrete roughly coincided with the ultimate strength of plain concrete. Above this limit, the damage
accumulation and plastic deformations proceeded in the confined specimens. This fact was evidenced by the increasing slope
of deformation diagrams in unloadings and repeated loadings and by the pronounced residual strains. The limit of linearity
could be raised significantly by pretension of the carbon yarns during their winding.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 21–44, January–February, 2006. 相似文献
14.
Anchorage strength models for end-debonding predictions in RC beams strengthened with FRP composites
The increase in the flexural capacity of RC beams obtained by externally bonding FRP composites to their tension side is often
limited by the premature and brittle debonding of the external reinforcement. An in-depth understanding of this complex failure
mechanism, however, has not yet been achieved. With specific regard to end-debonding failure modes, extensive experimental
observations reported in the literature highlight the important distinction, often neglected in strength models proposed by
researchers, between the peel-off and rip-off end-debonding types of failure. The peel-off failure is generally characterized
by a failure plane located within the first few millimetres of the concrete cover, whilst the rip-off failure penetrates deeper
into the concrete cover and propagates along the tensile steel reinforcement. A new rip-off strength model is described in
this paper. The model proposed is based on the Chen and Teng peel-off model and relies upon additional theoretical considerations.
The influence of the amount of the internal tensile steel reinforcement and the effective anchorage length of FRP are considered
and discussed. The validity of the new model is analyzed further through comparisons with test results, findings of a numerical
investigation, and a parametric study. The new rip-off strength model is assessed against a database comprising results from
62 beams tested by various researchers and is shown to yield less conservative results.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 373–388, May–June, 2008. 相似文献
15.
A. V. Motavkin L. L. Shcheglov N. G. Egorov B. S. L'vov 《Mechanics of Composite Materials》1968,4(4-6):833-838
The effect of structural parameters — length, diameter, and distribution of the reinforcing elements — on the mechanical characteristics of glass-reinforced plastics is investigated with reference to the case of glass laminates with randomly distributed, straight, uncut glass fibers in parallel planes. It is shown that the reduced strength of these laminates as compared with unidirectional material is associated with the redistribution of the load between the fibers and the resin and the relative reduction in the number of fibers in the cross section. A formula is proposed for estimating the strength of glass-reinforced plastics with a random distribution of the fibers in parallel planes.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Glass Fiber, Moscow Region. Moscow Bauman Higher Technical College. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1043–1050, November–December, 1968. 相似文献
16.
V. L. Kulakov Yu. M. Tarnopol’skii D. D. Mungalov A. I. Beyle 《Mechanics of Composite Materials》2000,36(3):199-206
The effective deformative characteristics of spatially reinforced composites made by spatial braiding along the generatrices
of a one-sheet hyperboloid are analyzed. The geometrical relationships determining the structure of a unit cell of a braided
composite are derived. The effective thermoelastic characteristics are calculated by the method of orientational averaging.
The dependences of the bending and torsional stiffnesses of thick-walled cylindrical rods — made by the method suggested and
by winding — on the braiding/winding angle are compared. The numerical estimations are given for rods made of carbon (CFRP)
and aramid (AFRP) epoxy plastics.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompzitnykh Materialov, Vol. 36, No. 3, pp. 341–354, May–June, 2000. 相似文献
17.
V. P. Tamuzh 《Mechanics of Composite Materials》1969,5(1):79-87
Research progress on the dynamic fatigue of plastics is briefly reviewed. Attention is concentrated on the problems of damage accumulation and self-heating. The effect of various factors on the fatigue of plastics is considered. The possibility of predicting the cyclic life-time from the results of long-time static strength tests is examined. The prospects for the construction of a theory of fatigue strength in complex states of stress are weighed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 97–107, January–February, 1969. 相似文献
18.
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
19.
A. B. Mitkevich 《Mechanics of Composite Materials》2006,42(4):297-302
The deformation of pressure vessel domes in asymmetric winding with the use of two families of yarns is accompanied by shear
deformations and torsion. For the case of large deformations, a system of equations for describing the stress-strain state
of an asymmetrically reinforced netlike shell of revolution loaded with an internal pressure is obtained. It is shown that
the shear deformations depend on the deformations of both the yarn families and the deformations of meridians and parallels
of the shell. As an example, the dome of a pressure vessel in a deformed state is calculated for an initial equilibrium shape
determined on the assumption that the yarns are inextensible.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 425–432, July–August, 2006. 相似文献
20.
A. B. Mitkevich 《Mechanics of Composite Materials》2005,41(6):497-504
Errors in the programs of winding pressure vessels can lead to an asymmetric reinforcement structure, which affects the equilibrium
shape of their domes and the tension in the left and right families of filaments. In this paper, equations determining the
equilibrium shape of the domes, the tension in filaments, and the shear stresses between layers are obtained. Examples with
winding trajectories in the form of geodesics and constant-deviation lines are considered. It is found that, for pressure
vessels, in the absence of external torque, the tension levels in filaments of the left and right families differ considerably.
It is also revealed that, for actual friction coefficients in winding, the shear stresses taken up by the binder are insignificant.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 743–752, November–December, 2005. 相似文献