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1.
A successful material design process for novel textile reinforced composites requires an integrated simulation of the material behaviour and the estimation of the effective properties used in a macroscopic structural analysis. In this context the Extended Finite Element Method (X-FEM) is used to model the behavior of materials that show a complex structure on the mesoscale efficiently. A homogenization technique is applied to compute effective macroscopic stiffness parameters. This contribution gives an outline of the implementation of the X-FEM for complex multi-material structures. A modelling procedure is presented that allows for the automated generation of an extended finite element model for a specific representative volume element. Furthermore, the problem of branching material interfaces arising from complex textile reinforcement architectures in combination with high fibre volume fractions will be addressed and an appropriate solution is proposed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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UD xFRP composites, i.e., isotropic plastics reinforced with long transversely isotropic fibres packed unidirectionally according
to the hexagonal scheme are considered. The constituent materials are geometrically and physically linear. The previous formulations
of the exact stiffness theory of such composites are revised, and the theory is developed further based on selected boundary-value
problems of elasticity theory. The numerical examples presented are focussed on testing the theory with account of previous
variants of this theory and experimental values of the effective elastic constants. The authors have pointed out that the
exact stiffness theory of UD xFRP composites, with the modifications proposed in our study, will be useful in the engineering
practice and in solving the current problems of the mechanics of composite materials.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 109–144, January–February, 2009. 相似文献
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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
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Textile reinforced concrete (TRC) is a composite of textile structures made of multi-filament yarns (rovings) within a cementitious matrix. Experimental investigations of textile reinforced concrete specimen show very complex failure mechanisms on different length scales. Therefore mechanical models on the micro, meso and macro scale are introduced. The paper presents a hierarchical material model of TRC on three scales. While on the micro scale the individual filaments of the fiber bundles are distinguished to determine an effective roving behavior, models on the meso scale are used to predict the macroscopic response of the composite material. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
The shear failure of reinforced concrete beams needs more attention than the bending failure since no or only small warning
precedes the failure. For this reason, it is of utmost importance to understand the shear bearing capacity and also to be
able to undertake significant rehabilitation work if necessary. In this paper, a design model for the shear strengthening
of concrete beams by using fiber-reinforced polymers (FRP) is presented, and the limitations of the truss model analogy are
highlighted. The fracture mechanics approach is used in analyzing the bond behavior between the FRP composites and concrete.
The fracture energy of concrete and the axial rigidity of the FRP are considered to be the most important parameters. The
effective strain in the FRP when the debonding occurs is determined. The limitations of the anchorage length over the cross
section are analyzed. A simple iterative design method for the shear debonding is finally proposed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 357–372, May–June, 2008. 相似文献
8.
Within the framework of fractal analysis and percolation theory, an alternative model of reinforcement of filled polymers
is offered. Practically, this model can be used only to describe the reinforcement of nanocomposites, because, according to
the treatment considered, a pronounced reinforcement can be reached only at ratios of filler particle diameter to the statistical
segment length of about 10 and less. A theoretical calculation showed a good qualitative and quantitative agreement with experiments.
The type of reinforcement mechanism of composites is determined by the type of the space (fractal or Euclidean) in which the
structure of the polymeric matrix is formed.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 797–802, November–Decem ber, 2006. 相似文献
9.
A simple procedure is proposed for the assessment of reinforced rectangular concrete columns under combined biaxial bending
and axial loads and for the design of a correct amount of FRP-strengthening for underdesigned concrete sections. Approximate
closed-form equations are developed based on the load contour method originally proposed by Bresler for reinforced concrete
sections. The 3D failure surface is approximated along its contours, at a constant axial load, by means of equations given
as the sum of the acting/resisting moment ratio in the directions of principal axes of the sections, raised to a power depending
on the axial load, the steel reinforcement ratio, and the section shape. The method is extended to FRP-strengthened sections.
Moreover, to make it possible to apply the load contour method in a more practical way, simple closed-form equations are developed
for rectangular reinforced concrete sections with a two-way steel reinforcement and FRP strengthenings on each side. A comparison
between the approach proposed and the fiber method (which is considered exact) shows that the simplified equations correctly
represent the section interaction diagram.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 443–462, May–June, 2008. 相似文献
10.
The structural situation of corners of a laminate reinforcement patch can cause singularities in the mechanical in-plane fields
due to the geometry and different material properties in the reinforced and nonreinforced domains, respectively. In the present
study, an asymptotic analysis of the cross-sectional force fields near the corners of a laminate reinforcement patch is performed.
Using the complex potential method based on Lekhnitskii’s approach, the mechanical in-plane fields at a two-dimensionally
modeled interface corner can be determined in a closed-form manner. Various configurations of interface corners are examined,
and their effect on the singular characteristics of the cross-sectional force field is studied. In particular, the size effect
of the reinforcement patch is considered.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 319–338, May–June, 2007. 相似文献
11.
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
12.
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
13.
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
14.
The problem on the elastoplastic deformation of reinforced shells of variable thickness under thermal and force loadings is
formulated. A qualitative analysis of the problem is carried out and its linearization is indicated. Calculations of isotropic
and metal composite cylindrical shells have shown that the load-carrying capacity of shell structures under elastoplastic
deformations is several times (sometimes by an order of magnitude) higher than under purely elastic ones; the heating of shells
with certain patterns of reinforcement sharply reduces their resistance to elastic deformations, but only slightly affects
their resistance to elastoplastic ones; not always does the reinforcement in the directions of principal stresses and strains
provide the greatest load-carrying capacity of a shell; there are reinforcement schemes that ensure practically the same resistance
of shells at different types of their fastening.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 707–728, November–December, 2006. 相似文献
15.
We propose a model for heat conduction of a spatially reinforced medium and present its generalization to the case of a polyreinforced
layer. We consider the heat-conduction equations for fibrous shells and construct a procedure for reduction of a three-dimensional
problem of heat conduction to a two-dimensional one. Analytic solutions of a stationary problem of heat conduction are found
for thin conic shells of revolution for various structures of reinforcement, and a graphical comparison of the corresponding
results is performed. We study one of the approaches to rational reinforcement of thin shells, according to which the thermal
“transparency” of a shell in the transverse direction is taken as a criterion of rational design.
Institute of Mathematics, Ukrainian Academy of Sciences, Kiev. Translated from Matematychni Metody ta Fizyko-Mekhanichni Polya,
Vol. 41, No. 2, pp. 132–150, April–June, 1998. 相似文献
16.
S Karabuk 《The Journal of the Operational Research Society》2008,59(4):510-520
Textile manufacturing consists of yarn production, fabric formation, and finishing and dyeing stages. The subject of this paper is the yarn production planning problem, although the approach is directly applicable to the fabric production planning problem due to similarities in the respective models. Our experience at an international textile manufacturer indicates that demand uncertainty is a major challenge in developing yarn production plans. We develop a stochastic programming model that explicitly includes uncertainty in the form of discrete demand scenarios. This results in a large-scale mixed integer model that is difficult to solve with off-the-shelf commercial solvers. We develop a two-step preprocessing algorithm that improves the linear programming relaxation of the model and reduces its size, consequently improving the computational requirements. We illustrate the benefits of a stochastic programming approach over a deterministic model and share our initial application experience. 相似文献
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Yu. M. Pleskachevskii A. O. Shimanovskii G. M. Kuzemkina 《Mechanics of Composite Materials》2008,44(3):209-214
A finite-element model of a reinforced concrete beam with rebars modeled by a 3-D deformable body has been developed. An analysis
of the stress-strain state of the beam allowed us to determine the stress distribution on cross sections of the rebars and
the location of zones with cracks in concrete. It is found that the break of bond between the reinforcement and concrete goes
outside the areas of intensely cracked concrete matrix.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 309–316, May–June, 2008. 相似文献
18.
D. P. Aleksandrov 《Mechanics of Composite Materials》2005,41(6):541-552
The mechanical state of a press-powder filler for pyroautomatics system units of aerospace equipment during their long-term
storage is investigated. With the use of the endochronic approach, the rheological properties of a dispersedly reinforced
composite are simulated based on the conceptions of linear and nonlinear creep. Analytical expressions of constitutive relations
of creep and strength for the composites are obtained.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 803–818, November–December, 2005. 相似文献
19.
To a given finite graph we associate three kinds of adic, or Bratteli–Vershik, systems: stationary, symbol-count, and reinforced.
We give conditions for the natural walk measure to be adic-invariant and identify the ergodic adic-invariant measures for
some classes of examples. If the walk measure is adic-invariant, we relate its ergodic decomposition to the vector of limiting
edge traversal frequencies. For some particular nonsimple reinforcement schemes, we calculate the density function of the
edge traversal frequencies explicitly. 相似文献
20.
Artificial neural network models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the casting methods. An understanding of the inter-relationships between input variables is essential for interpreting the sensitivity data and optimizing the design parameters. Aluminum is the best metal for producing metal matrix composites which are known as one of the most useful and high-tech composites in our world. Combining aluminum and nano Al2O3 particles will yield a material with high mechanical and tribological properties. In this investigation, the accuracy of various artificial neural network training algorithms in FEM modeling of Al2O3 nano particles reinforced A356 matrix composites has been studied. 相似文献