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1.
A boundary-discontinuous Fourier expansion method to analyze the displacements and stresses in cross-ply composite laminates
with transverse cracks is presented. The governing equations of the problem are derived on the basis of the generalized plane
strain assumption and two-dimensional equations of elasticity. By employing the boundary-discontinuous Fourier expansion method,
the governing equations in the form of coupled high-order ODEs are transformed to a set of systems of linear algebraic equations.
The method is used to obtain solutions for which published results can be found for comparisons. Compared with the conventional
numerical methods for solving coupled high-order ODEs, the method presented is more efficient. Further parametric studies
are carried out for cracked laminates with various geometric and material properties.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 795–826, November–December, 2008. 相似文献
2.
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
3.
Moment redistribution in continuous reinforced concrete beams strengthened with carbon-fiber-reinforced polymer laminates 总被引:1,自引:0,他引:1
The results of tests on continuous steel-fiber-reinforced concrete (RC) beams, with and without an external strengthening,
are presented. The internal flexural steel reinforcement was designed so that to allow steel yielding before the collapse
of the beams. To prevent the shear failure, steel stirrups were used. The tests also included two nonstrengthened control
beams; the other specimens were strengthened with different configurations of externally bonded carbon-fiber-reinforced polymer
(CFRP) laminates. In order to prevent the premature failure from delamination of the CFRP strengthening, a wrapping was also
applied. The experimental results obtained show that it is possible to achieve a sufficient degree of moment redistribution
if the strengthening configuration is chosen properly, confirming the results provided by two simple numerical models.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 667–686, September–October, 2007. 相似文献
4.
Short pulsed laser milling is a novel method to process the carbon fiber reinforced plastics (CFRP) which has bad machinability. This paper presents a numerical model studying the material removal mechanism of CFRP laser milling. It is confirmed by both the experiment and the simulation that laser ablation and mechanical erosion caused by the polymer pyrolysis are all involved in the material removal. Because the heating and cooling rate in short pulsed laser milling is high, ablation of two adjacent laser pulses almost has little influence on each other. By conducting the parametric analysis, it was found that the spacing distance under which the matrix between two adjacent laser pulses was completely degraded should be adopted to utilize the mechanical erosion effectively. Laser milling experiments of CFRP laminates were performed using a nanosecond pulsed laser system. The established model could predict the average ablation depth per scanning pass at an optimal spacing distance. 相似文献
5.
M. I. Zelikin 《Journal of Mathematical Sciences》2011,177(2):270-298
New constructions of fields of extremals for multiple integrals and new versions of the Legendre–Weyl–Carathéodory transform
are introduced. The connection and the curvature of fiber bundles on which multiple integrals are defined are calculated. 相似文献
6.
V. S. Ekel’chik 《Mechanics of Composite Materials》2008,44(2):109-120
The Barr’s refined theory of torsional vibrations of isotropic rods of noncircular cross section is generalized for an orthotropic
material. An analysis of natural frequencies of torsional vibration of free-free orthotropic prismatic rods of rectangular
cross section is carried out with the help of an exact solution of the frequency equation. For orthotropic CFRP and GFRP rods,
the improved theory, which takes into account the normal stresses and inertia forces in the axial direction, in some cases,
predicts a noticeable raise in the natural frequencies compared with those following from the Saint-Venant classical theory.
A good agreement is obtained between the experimental and calculated values of natural frequencies of torsional vibrations
of rectangular quartz and fiber glass rods. The dispersion of torsional waves in an orthotropic quasi-homogeneous rod is considered.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 165–182, March–April, 2008. 相似文献
7.
M. Frauenhofer T. Ströhlein S. Fabig S. Böhm L. Herbeck K. Dilger 《Mechanics of Composite Materials》2008,44(5):523-530
The prepreg technology is a state-of-the-art method to produce high-performance CFRP parts. Due to the high material prices,
the restricted process rate, and limitations to the component complexity, in future, more and more parts will be assembled
by using liquid composite moulding. Especially in the case of series larger than 100 parts per year, the LCM technology offers
the best cost-effectiveness. This technology is based on resin injection into dry multilayer fibre textiles (preforms). The
Institute of Joining and Welding (TU, Braunschweig), together with the Institute of Composite Structures and Adaptive Systems
(DLR), has elaborated a new technology to speed up the preform process, which is the most labour-intensive step within the
LCM process chain. A novel concept to consolidate binder-coated fabrics is under development. By applying the high energy
transfer rate of induction technology, it is possible to heat up a preform with rates up to 50 K/s to melt the binder and
consolidate the preform.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 747–756, September–October, 2008. 相似文献
8.
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
9.
During service loading of cross-ply laminates, transverse cracks occur in plies. The cracks parallel to the fiber direction are extended over the full thickness of transverse plies and often cross the entire test specimen width. It is widely recognized that the changes of laminate thermomechanical constants, caused by the transverse cracking of composite laminates, can be significant. Theoretical stress analysis in the cross-ply laminates in the vicinity of cracks is performed using numerical (FE) and analytical methods. The effect of transverse cracks on the degradation of elastic properties will be discussed in Part 2 [1]. Approximate analytical micromechanical models based on shear lag predictions, variational analysis, and numerical 2D finite element calculations were verified in their predictive abilities. The three variational models used are based on the principle of minimum complementary energy and have different degrees of accuracy with respect to the stress assumptions used (Hashin's, 2D 0° and 2D 0°/90° models). Using FEM, the plane stress and strain state were analyzed. The effect of material properties and layer thickness on the stress distribution in a 90° layer was evaluated by varying the crack spacing. The crack opening displacement (COD), normalized with respect to the far field strain, is proposed as a measure of reduction of the mechanical properties. Since the CODs are rather insensitive to the crack spacing (crack density) in a wide region, they will be used in modeling the stiffness reduction in these laminates [1].Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 6, pp. 796–820, November–December, 1997. 相似文献
10.
E. G. Sklyarenko 《Journal of Mathematical Sciences》2006,136(5):4166-4200
The classical theory of Thom isomorphisms is extended to nonorientable vector bundles. The properties of orientation sheaves
of bundles and of the Thom and Euler classes τ and e with respect to projections, fiber maps, Cartesian products, and Whitney sums of bundles are studied. The validity of standard
constructions used in the applications of the classes τ and e is confirmed. It is shown that the Thom isomorphisms, together with their form, are consequences of the Poincaré duality.
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Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 9, No. 4, pp. 55–103, 2003. 相似文献
11.
D. G. Katerelos P. Lundmark J. Varna C. Galiotis 《Mechanics of Composite Materials》2006,42(6):535-546
The matrix cracking models developed for cross-ply composite laminates have been poorly extended in the past to more complex
geometries used in practice, and they are still under development. In this paper, a new detailed analysis of the effect of
matrix cracking on the behaviour of cross-ply and [0/45]s laminates under uniaxial tension is attempted. The model used in this work is applicable both to cross-ply laminates and
unbalanced systems. It gives exact closed-form expressions for all thermomechanical properties of a general symmetric laminate
with cracks in arbitrary layers. The theoretical approach is backed by experimental data obtained by microscopic strain-state
variation measurements within a specimen, with using the technique of laser Raman spectroscopy. Glass-fibre-reinforced epoxy
systems were investigated. Embedded aramid fibres-sensors within the 0° ply and near the 0°/θ ° interface were necessary due to the poor Raman signal of glass. Using experimental Raman data, the residual strain and the
stiffness reduction are determined as functions of increase in crack density. The stiffness reduction is predicted with a
high accuracy, whereas the measured residual strains are larger than predicted. The good results for the reduction in the
elastic modulus show that the basic assumption of the model is accurate. The difference is explained by the viscoelastic-viscoplastic
behaviour of the off-axis layer in shear, which in creases the “apparent” residual strain.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 771–786, November–December, 2006. 相似文献
12.
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
13.
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
14.
The equivariant cohomology ring of a GKM manifold is isomorphic to the cohomology ring of its GKM graph. In this paper we
explore the implications of this fact for equivariant fiber bundles for which the total space and the base space are both
GKM and derive a graph theoretical version of the Leray–Hirsch theorem. Then we apply this result to the equivariant cohomology
theory of flag varieties. 相似文献
15.
R. A. Kayumov 《Mechanics of Composite Materials》1999,35(5):409-418
Laminated nonthin shells made of nonlinearly elastic fiber composites are considered. The composite material is assumed to
be transversely isotropic in planes perpendicular to reinforcement. The asymptotic method and the condition of material stability
are applied to analyze the structure of constitutive relations. To introduce a small parameter, the high stiffness in the
reinforcement direction of the fiber composite is used. This allows us to obtain simplified constitutive relations containing
functions with one or two arguments instead of five as in the initial general case.
Kazan State Architectural Building Academy, Tatarstan, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35,
No. 5, pp. 615–628, September–October, 1999. 相似文献
16.
Carbon fiber reinforced plastics (CFRP) are mostly used in multilayered laminates, which consist of several very thin layers stacked over each other. For such laminated structures, delamination represents one of the most critical states of failure. In order to predict both the onset as well as the propagation of delamination, a cohesive zone-like continuum damage model is proposed in this paper. This damage model is directly incorporated into a solid-shell finite element with finite thickness. Further, the formulation is capable of considering the interaction of different failure modes. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
18.
Y. I. Kunets V. V. Matus V. V. Mykhas’kiv A. Boström Ch. Zhang 《Mechanics of Composite Materials》2008,44(2):165-172
The problem of interaction of a plane time-harmonic SH-wave with an elastic fiber of quasi-square or quasi-triangular cross
section, when an interface crack is present between an infinite elastic matrix and the fiber, is considered. The modified
null-field method taking into account the asymptotic behavior of the solution at crack tips is exploited for obtaining numerical
results. The effects of fiber shape, fiber/matrix material combination, debonding (crack size), and direction of wave incidence
on the scattering amplitude in the far zone are analyzed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 245–254, March–April, 2008. 相似文献
19.
S. S. Akavci 《Mechanics of Composite Materials》2005,41(5):445-460
In this study, various theories of composite laminated plates are extended to rectangular composite laminates resting on an
elastic foundation. First, an analysis based on the classical theory of laminated plates is employed. Then the first-order
Reissner-Mindlin theory is used for analyzing the laminates. At last, the Reddy shear deformation theory, which allows for
the transverse shear strains, is applied to the bending analysis of the laminates. In the analysis, the two-parameter Pasternak
and Winkler foundations are considered. The accuracy of the present analysis is demonstrated by solving problems numerical
results for which are available in the literature. Some numerical examples are presented to compare the three methods and
to illustrate the effects of parameters of the elastic foundations on the bending of shear-deformable laminated plates.
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Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 5, pp. 663–682, September–October, 2005. 相似文献
20.
A problem for an interface crack located in a layered magnetoelectroelastic material strip of semi-infinite length is solved.
A closed-form solution is obtained for anti-plane mechanical and in-plane electric and magnetic fields. Explicit expressions
for stresses and electric and magnetic fields, together with their intensity factors and the energy release rate, are obtained.
The extreme cases of impermeable and permeable cracks are discussed. Using the basic solution for a single crack, solutions
for two collinear interface cracks in an infinitely long layered magnetoelectroelastic medium, an interface crack in an infinitely
long layered magnetoelectroelastic medium, and an edge crack at the interface of a semi-infinitely long layered magnetoelectroelastic
medium are also obtained.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 145–164, March–April, 2008. 相似文献