共查询到20条相似文献,搜索用时 46 毫秒
1.
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
2.
The paper presents results of an experimental investigations carried out to estimate the cooperation between a steel bar reinforcement
and round concrete cylinders confined by a carbon-epoxy composite, concerning the increase in the concrete compression strength
due the composite wrapping. The steel bar reinforcement with its yield stress considerably increases the bearing capacity
of concrete. This also happens above the unconfined concrete strength of specimens. The onset of reinforcement yielding roughly
coincides with reaching of the unconfined concrete strength at a compressive strain of ≈0.20%, and therefore it does not produce
a change in the tangent modulus of the stress-strain relationships above the limit of linearity.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 293–308, May–June, 2007. 相似文献
3.
The ultrasonic nondestructive evaluation of composite cylinders requires a thorough understanding of the propagation of waves
in these materials. In this paper, the propagation of flexural and longitudinal guided waves in fiber-reinforced composite
(FRC) rods with transversely isotropic symmetry properties is studied. The frequency equations obtained for free cylinders
and the effect of increased fiber volume fraction (increased anisotropy) on the dispersion characteristics of the rod are
explored. The numerical results reveal a number of previously unnoticed characteristics of dispersion curves for composite
cylinders. The mode shapes of longitudinal waves propagating in glass/epoxy cylinders are also plotted. These plots can be
used to choose an appropriate strategy for inspecting composite cylinders by ultrasonic nondestructive evaluation techniques.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 411–426, May–June, 2007. 相似文献
4.
The paper deals with numerical and experimental investigations of steel made hulls crimped onto glass fibre reinforced plastic rods. The aim is to optimize the crimping procedure to realize maximum pull out forces of the specimens. The numerical simulations were performed with the commercial FEA package ABAQUS. For the contact formulation a Coulomb friction law with a constant friction coefficient was applied. The damage and fracture states within the composite rods due to the crimping process were investigated by scanning electron microscopy. The results obtained were discussed and an outlook to further work is given. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
Slawomir Zolkiewski 《PAMM》2012,12(1):163-164
In this paper the research results of hybrid composite materials made of a steel plate and laminates are presented. The tested composites were made of a metal sheet plate and a laminate plate connected by means of barbed studs. The laminates were made of three different types of fabrics with: fibreglass, carbon fibres and aramid fibres. As a warp, epoxide resin and polyester resin were used. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Christopher M. Pastore 《Mechanics of Composite Materials》2000,36(2):97-116
For several decades researchers have been interested in textile processes for the production of composite reinforcement. These
technologies have offered several promises: reduced fabrication costs, 3-D multiaxial reinforcement, and damage tolerance.
Despite these advantages, textile composites have not reached the level of implementation of laminated composites. In this
paper, the opportunities provided by textile reinforced composites and the challenges that limit their implementation will
be discussed in detail. Textile composites refer to a family of processes: weaving, braiding, knitting, and hybrids thereof.
The various families of textiles will be defined and the basics of fabric formation for each family will be detailed. In particular,
the strengths and weaknesses of each manufacturing technique will be addressed to provide a view of the applicability of each
technology. This will include some guidance on shape formation capability, property ranges, size limitations, and estimates
of cost to produce. Potential applications for these materials will be presented. Among the limitations on the application
of textile reinforced composites is the lack of adequate modeling capabilities for these materials. Textile composites have
rather large unit cell structures and are highly inhomogeneous throughout their volumes. These features provide benefits in
manufacturing, but require novel modeling techniques to correctly understand the mechanical behavior. A review of analytical
techniques applied to textile composites will be presented along with a discussion of the benefits and weaknesses of each
of these methods. The enabling technologies needed to further the implementation of textile composites in structural applications
will be discussed.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 165–194, March–April, 2000. 相似文献
7.
Resonance methods for determining the complex shear moduli of orthotropic composites 总被引:1,自引:1,他引:0
V. S. Ekel’chik 《Mechanics of Composite Materials》2007,43(6):487-502
A survey of various methods for determining the complex elasticity and shear moduli from the resonant frequencies of flexural
and torsional vibrations of rectangular rods cut out from a plate of an orthotropic composite is presented. The errors in
the computed values of dynamic shear moduli caused by inaccuracies in the experimental determination of resonance frequencies
are examined. A new variant of the resonance method is developed, which permits one to find three complex shear moduli of
a composite from the resonant frequencies and the damping of torsional vibrations of three rods oriented along three symmetry
axes of the material. For computing the moduli in the case of an overdetermined system, an algorithm of nonlinear optimization
based on the least-squares method is recommended. From the results obtained it follows that, for determining the interlaminar
shear moduli with a necessary accuracy, the rods must be sufficiently thick. It is shown that a good agreement alone between
calculated and experimental frequencies of flexural and torsional vibrations of rods does not ensure a reliable determination
of the moduli of interlaminar shear if experiments are carried out on wide test specimens cut out from a thin plate. Recommendations
are given for the choice of geometrical sizes of test specimens for resonance experiments.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 721–744, November–December, 2007. 相似文献
8.
Skudra A. M. Skudra A. A. Bulavs F. Kruklinsh A. 《Mechanics of Composite Materials》2001,37(2):139-144
Beams of cement-based composites reinforced with different types of meshes usually do not have stirrups. With good anchoring of the longitudinal tensile reinforcement, such beams break after the development of a critical inclined crack caused by the principal tensile stresses. In this paper, the mechanics of development of such cracks is studied. The results of theoretical investigation based on the structural mechanics of laminates are compared with the results of experimental testing of cement-based composite beams reinforced with punched steel grids. 相似文献
9.
Calculation and Experimental Study of a Two-Way Reinforced Rubber-Cord Composite in Tension 总被引:1,自引:0,他引:1
A rubber-cord composite, reinforced in two directions with fibers of polyamide cord, under large tensile deformations is investigated based on calculations of a rubber-cord composite material and on tensile tests of specimens made of the casing of a diagonal truck tire. A method of the experimental tensile testing of rubber-cord composite specimens is described. The calculations are based on the carcass theory of composite materials. The calculated and experimental parameters of the macroscopic strains of the rubber tire cord and of its structure in a deformed configuration are given. The manifestation of edge effects in relation to the reinforcement angle is described. 相似文献
10.
R. Tepfers V. Tamužs R. Apinis U. Vilks J. Modniks 《Mechanics of Composite Materials》1996,32(2):113-121
Reinforcing units, FRP, of unidirectional fiber composites for concrete have elastic behavior up to tensile failure. For safety reasons an elongation of 3% at maximum load is usually required for the reinforcement. Ductile behavior with the necessary elongation and stress hardening could be obtained with braided fiber strands around a core of foam plastic, thin glass fiber cylindrical shell, or unidirectional carbon fibers. Braids around a porous core reveal the ductility when epoxy resin breaks up and collapse of core enables the braids to rotate. The same seems to happen at that cross section, where carbon fiber core breaks in tension. The best result is obtained using a cylindrical glass fiber reinforced core shell surrounded with aramid fiber braid.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Division of Building Materials, Chalmers University of Technology, S412 96 Göteborg, Sweden. Institute of Polymer Mechanics, Latvian Academy of Sciences, Riga, LV-1006 Latvia. Published in Mekhanika Kompozitnykh Materialov, Vol. 32, No. 2, pp. 167–179, March–April, 1996. 相似文献
11.
The application of FRP rods as an internal or external reinforcement in new or damaged concrete structures is based on the development of design equations that take into account the mechanical properties of FRP material systems.The measurement of mechanical characteristics of FRP requires a special anchoring and protocol, since it is well known that these characteristics depend on the direction and content of fibers. In this study, an effective tensile test method is described for the mechanical characterization of FRP rods. Twelve types of glass and carbon FRP specimens with different sizes and surface characteristics were tested to validate the procedure proposed. In all, 79 tensile tests were performed, and the results obtained are discussed in this paper. Recommendations are given for specimen preparation and test setup in order to facilitate the further investigation and standardization of the FRP rods used in civil engineering. 相似文献
12.
V. M. Akhundov 《Mechanics of Composite Materials》2007,43(2):159-172
Equations for a round cylinder weakly reinforced with systems of yarns and subjected to large tensile, inflation, and torsional
deformations are presented. Since the degree of filling is small, the model of uniaxial stress state is assumed. The fibers
are aligned with spirals on cylindrical surfaces and with radii in the transverse and meridional sections of the cylinder.
The equations are obtained in the macroscopically unidimensional statement for the case of cylindrically symmetric strains.
Numerical results are given for twisted hollow rubber cylinders reinforced with polymer yarns in the axial and radial directions.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 2, pp. 237–256, March–April, 2007. 相似文献
13.
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
14.
A. P. Marukhin 《Mechanics of Composite Materials》2007,43(6):561-572
A method of primers is elaborated which allows one to calculate the distribution function of durability of a composite material
in tension in the reinforcement direction. Integral and differential equations for calculating the probabilities of formation
of primers and destruction of a material caused by their formation are presented. Distribution functions of material strength
for the parameter of Weibull distribution of fiber strength on the interval 2.1 ≤ β
f ≤ 50.1 are calculated. From the functions, the average values and root-mean-square deviations of material strength are found.
The results obtained agree well with calculations by using the structural-imitation simulation. The distribution functions
of material strength with a high precision are approximated by the three-parameter Weibull distributions. The distribution
parameters are approximated by the linear functions of ln (βf).
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 823–838, November–December, 2007. 相似文献
15.
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
16.
The first part of the paper deals with homogenization models of unidirectional composites, in which each phase of the material
is bounded by parallel cylindrical surfaces. For a GFRP with epoxy resin and glass fibres, five elastic constants for six
models of the composite are calculated. In the second part, the results of strain gauge tests, photoelasticity investigations,
and scanning electron inspection are discussed. With these data, some elastic constants of the composite in tension and compression
are found. A comparison of experimental and analytical results is presented.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 195–206, March–April, 2008. 相似文献
17.
The intralaminar fracture toughness of a unidirectionally reinforced glass/epoxy composite is determined experimentally at
several mode I and mode II loading ratios. The crack propagation criterion, expressed as a quadratic form in terms of single-mode
stress intensity factors (alternatively, linear in terms of energy release rates), approximates the test results reasonably
well. The mixed-mode cracking criterion obtained is used to predict the intralaminar crack on set in a cross-ply glass/epoxy
composite under off-axis tensile loading.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 785–794, November–December, 2008. 相似文献
18.
The stability problem is solved for cylindrical shells made of a laminated composite whose directions of layer reinforcement
are not aligned with coordinate axes of the shell midsurface. Each layer of the composite is modeled by an anisotropic material
with one plane of symmetry. The resolving functions of the mixed variant of shell theory are approximated by trigonometric
series satisfying boundary conditions. The stability of the shells under axial compression, external pressure, and torsion
is investigated. A comparison with calculation data obtained within the framework of an orthotropic body model is carried
out. It is shown that this model leads to considerably erroneous critical loads for some structures of the composites.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 5, pp. 651–662, September–October, 2005. 相似文献
19.
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
20.
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.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 285–300, May–June, 2006. 相似文献