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1.
Results from an experimental study on the delamination of a unidirectional carbon fiber/epoxy composite by using the four-point
bend end-notched flexure (4ENF) test are presented. It was found that the compliance data obtained in load-unload-reload and
continuous loading tests were very similar. The R-curves for specimens of different thickness were also found experimentally.
These curves showed an appreciable toughening with crack advance, which can be explained by the presence of fiber bridging.
The finite-element method with cohesive elements allowing us to model the progressive delamination was used to analyze the
4ENF test.
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Russian translated published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 5, pp. 573–584, September–October, 2005. 相似文献
2.
L. E. T. Ferreira 《Mechanics of Composite Materials》2007,43(5):479-486
This paper addresses the use of R-curves to study the fracture behavior of high-strength concrete and steel-fiber-reinforced
concrete subjected to crack ing in a three-point bending configuration. The R-curves are modeled through an effective approach
based on the equations of linear-elastic fracture mechanics (LEFM), which relates the applied load to the fundamental displacements
of notched-through beams loaded monotonically. It is initially shown that, for quasi-brittle materials, the R-curves responses
can be evaluated in a quasi-analytical way, using the load-crack mouth opening, the load-load line displacement, or exclusively
the displacement responses obtained experimentally. Afterward, the methodology is used to obtain the fracture responses of
high-strength and fiber-reinforced concretes, up to the final stages of rupture.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 701–710, September–October, 2007. 相似文献
3.
K. Simeonova 《Mechanics of Composite Materials》1996,32(4):368-373
On the basis of the theory of microbuckling of lamina-reinforced composites and formula predicting the critical composite stress for microbuckling in the shear mode
cs
published in the literature, a FORTRAN program for study of the behavior of microbuckling of fiber reinforced composites has been developed. Some types of composite materials (reinforcement of different fibers and epoxy matrix) have been studied. Graphics and curves, accounting for the dependences of the compressive stress at failure
cs
from the reinforcement volume k, specimen length L, and shear modulus of resin Gr have been obtained. The comparison of the theoretical diagrams presented here and experimental and theoretical results, published in the literature shows good agreement. The basic conclusion of the work presented here is that the study could be used for other fiber reinforced composites (with different mechanical properties of matrices and fibers).Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria. Published in Mekhanika Kompozitnykh Materialov, Vol. 32, No. 4, pp. 531–538, July–August, 1996. 相似文献
4.
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
5.
I. J. Gnip S. I. Vaitkus V. I. Kersulis S. A. Veyelis 《Mechanics of Composite Materials》2007,43(5):433-444
The results obtained in an experimental investigation of deformability of expanded polystyrene (EPS) under short-term compression
are presented. The density of EPS varied from 13 to 28 kg/m3. The method of design of experiments was used to determine the elastic modulus and the ultimate strain (corresponding to
the end of quasi-linear deformability) under compression stresses operating perpendicularly and parallel to the faces of EPS
products. A graphical interpretation of the models is also presented. Based on the experimental data obtained, it was concluded
that the expanded polystyrene was homogeneous in mutually perpendicular planes with respect to its deformability in compression.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 639–656, September–October, 2007. 相似文献
6.
A. C. Orifici R. S. Thomson R. Degenhardt C. Bisagni J. Bayandor 《Mechanics of Composite Materials》2007,43(1):9-28
Analysing the collapse of skin-stiffened structures requires capturing the critical phenomenon of skin-stiffener separation,
which can be considered analogous to interlaminar cracking. This paper presents the development of a numerical approach for
simulating the propagation of interlaminar cracks in composite structures. A degradation methodology was introduced in MSC.Marc,
which involved the modelling of a structure with shell layers connected by user-defined multiple-point constraints (MPCs).
User subroutines were written that employ the virtual crack closure technique (VCCT) to determine the onset of crack growth
and modify the properties of the user-defined MPCs to simulate crack propagation. Methodologies for the release of failing
MPCs are presented and are discussed with reference to the VCCT assumption of self-similar crack growth. The numerical results
obtained by using the release methodologies are then compared with experimental data for a double-cantilever beam specimen.
Based on this comparison, recommendations for the future development of the degradation model are made, especially with reference
to developing an approach for the collapse analysis of fuselage-representative structures.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 15–42, January–February, 2007. 相似文献
7.
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
8.
An analysis of the crack closure and fatigue crack growth rate have been carried out for an infinitely long poled piezoelectric
ceramic strip weakened by a straight hair line internal crack. The ceramic under consideration is assumed to be mechanically
more brittle. The crack faces are perpendicular to the poled direction of the strip. The crack faces open in Mode-I deformation
on account of in-plane tension applied to the edges of the strip together with either an in-plane electric displacement prescribed
on edges of the strip or a uniform constant electric field prescribed on its edges. As a result, a yield zone is formed ahead
of each tip of the crack. The yield zones developed are then arrested by applying a normal, cohesive, linearly varying yield
point-stress to their rims. For each case, the Fourier transform method is used to find a solution. The resulting integral
equations are solved numerically. Expressions are derived for the crack opening displacement and the crack growth rate. The
variations in these quantities are plotted in relation to the affecting parameters, viz., the strip thickness, the yield zone
length, the electric displacement, and material constants. A case study is presented graphically for PZT-4, PZT-5H, and BaTiO3 ceramics.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 647–664, September–October, 2008. 相似文献
9.
Michel C. Delfour 《Acta Appl Math》2012,118(1):161-183
In order to achieve prescribed drug release kinetics some authors have been investigating bi-phasic and possibly multi-phasic
releases from blends of biodegradable polymers. Recently, experimental data for the release of paclitaxel have been published
by Lao et al. (Lao and Venkatraman in J. Control. Release 130:9–14, 2008; Lao et al. in Eur. J. Pharm. Biopharm. 70:796–803, 2008). In Blanchet et al. (SIAM J. Appl. Math. 71(6):2269–2286, 2011) we validated a two-parameter quadratic ordinary differential equation (ODE) model against their experimental data from three
representative neat polymers. In this paper we provide a gradient flow interpretation of the ODE model. A three-dimensional
partial differential equation (PDE) model for the drug release in their experimental set up is introduced and its parameters
are related to the ones of the ODE model. The gradient flow interpretation is extended to the study of the asymptotic concentrations
that are solutions of the PDE model to determine the range of parameters that are suitable to simulate complete or partial
drug release. 相似文献
10.
A strip saturation model solution is obtained for a poled cracked piezoelectric ceramic plate. The plate is cut along a straight
finite hair line crack whose rims are perpendicular to the poling axis of the plate. A mechanical load and an electric field
applied open the rims of the crack and, as a result, saturation zones develop ahead of its tips. To arrest the crack from
further opening, a linearly varying saturation limit normal electrical displacement is prescribed on rims of the saturation
zones. The technique of complex variables is used to obtain the solution to the problem. A case study is presented for PZT-4,
PZT-5, and PZT-7 ceramics.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 85–92, January–February, 2009. 相似文献
11.
This paper develops a closed-form solution for an interface crack in a layered magnetoelectroelastic strip of finite width.
The strip is subjected to anti-plane mechanical and in-plane electric and magnetic fields. Explicit expressions for the stress,
electric, and magnetic fields, together with their intensity factors, are obtained for two extreme cases of an impermeable
and a permeable cracks. The stress intensity factor does not depend on the electromagnetic boundary conditions assumed for
the crack. However, the electrically and magnetically permeable boundary conditions on the crack profile have a significant
influence on the crack-tip electromagnetic field intensity factors. Solutions for some special cases, such as a central crack,
an edge crack, two symmetric collinear cracks, and a row of collinear interface cracks, are also obtained in closed forms.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 763–784, November–December, 2008. 相似文献
12.
The effect of hydrostatic pressure on the fracture toughness of disperse-reinforced composite materials is investigated. It
is shown that increased hydrostatic pressure leads to an increase in the critical value of the stress intensity factor and,
as a consequence, to an increase in the crack propagation rate. In this case, the pressure-time analogy method can be used
to describe the effect of hydrostatic pressure on the characteristics of the crack resistance. This method enables us to represent
the experimental data obtained in the form of a generalized dependence of the fracture toughness on the reduced loading rate.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 1, pp. 121–126, January–February, 2000. 相似文献
13.
A singular integral equation method is used to study the closure of edge cracks during bending of an isotropic half space.
The cases of a single crack and of a periodic system of cracks perpendicular to the edge of the half space are considered.
The effects of the free edge and the spatial period of the cracks on the distribution of the contact reaction and limiting
load are investigated. The numerical results are compared with published data obtained without taking crack closure into account,
as well as with results on the contact problem for bending of an infinite plate.
Ivano-Frankovsk Sector, Institute of Applied Mechanical and Mathematical Problems, National Academy of Sciences of Ukraine.
Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 29, pp. 83–89, 1999. 相似文献
14.
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
15.
A piezoelectric fiber/elastic matrix system subjected to axially symmetric mechanical and electric loads is considered. The
fiber contains a penny-shaped crack located at its center perpendicularly to the fiber. By using the Fourier and Hankel transforms,
the problem is reduced to the solution of an integral equation. Numerical solutions for the crack tip fields are obtained
for various crack sizes and different fiber volume fractions.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 301–318, May–June, 2006. 相似文献
16.
The stability of elastic columns subjected to axial pressure is studied. An elastic multistepped column with rectangular cross
sections are considered assuming that at the re-entrant corners of the column stable cracks are located. The influence of
a crack on the loss of stability of the column is described by means of local flexibility and the function of compliance coupled
with the stress intensity factor, which is known from the linear elastic fracture mechanics. A column with a single step is
studied in more detail. The influence of crack location and length on the buckling load is assessed numerically.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 87–100, January–February, 2006. 相似文献
17.
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
18.
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
19.
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
20.
The creep and long-time strength in interlaminar shear and the creep in compression in the direction of the reinforcement have been experimentally investigated for certain types of oriented glass-reinforced plastics. The specimens in the interlaminar creep tests took the form of short beams loaded in bending. The experimental creep data for shear and compression are well described by the hereditary theory with a kernel of the Abel type (shear) or in the form of a Rabotnov function (compression). If the stresses are constant in time, good agreement with experiment is also given by Findley's form of the aging theory. A deformation criterion of interlaminar shear strength is also obtained. The experimental curves and values of the creep and long-time strength constants are presented.Translated from Mekhanika Polimerov, No. 6, pp. 1003–1012, November–December, 1971. 相似文献