共查询到20条相似文献,搜索用时 15 毫秒
1.
The interlaminar fracture and the low-velocity impact behavior of carbon/epoxy composite materials have been studied using
width-tapered double cantilever beam (WTDCB), end-notched flexure (ENF), and Boeing impact specimens. The objectives of this
research are to determine the essential parameters governing interlaminar fracture and damage of realistic laminated composites
and to characterize a correlation between the critical strain energy release rates measured by interlaminar fracture and by
low-velocity impact tests. The geometry and the lay-up sequence of specimens are designed to probe various conditions such
as the skewness parameter, beam volume, and test fixture. The effect of interfacial ply orientations and crack propagation
directions on interlaminar fracture toughness and the effect of ply orientations and thickness on impact behavior are examined.
The critical strain energy release rate was calculated from the respective tests: in the interlaminar fracture test, the compliance
method and linear beam theory are used; the residual energy calculated from the impact test and the total delamination area
estimated by ultrasonic inspection are used in the low-velocity impact test. Results show that the critical strain energy
release rate is affected mainly by ply orientations. The critical strain energy release rate measured by the low-velocity
impact test lies between the mode I and mode II critical strain energy release rates obtained by the interlaminar fracture
test.
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. 195–214, March–April, 2000. 相似文献
2.
The damage behavior of laminated E-glass/epoxy beams, with and without an initial delamination, subjected to an axial impact
by a moving bullet has been investigated experimentally and numerically. The specimens were made from a unidirectional fiber
fabric stacked in the sequences [06]
s
, [±453]
s
, and [906]
s
, and a delamination was created in them by locating a copper foil at a specified position. The data on the bullet speed and
strain history were recorded by a laser setup, a high-speed dynamic strain indicator, and a TDS420A oscilloscope. It is shown
that the delamination and the ply stacking sequence play a significant role in the dynamic response and damage behavior of
laminated beams. A numerical simulation is performed by using the commercial finite-element software ABAQUS/Explicit, and
the results obtained are in a good agreement with experimental observations.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 49–64, January–February, 2009. 相似文献
3.
Xiaoqing Yan Shurong Ding J. W. Tong M. Shen Z. Huo 《Mechanics of Composite Materials》2009,45(3):293-302
A thermoplastic angle-ply AS4/PEEK laminate with a hole is considered. The interlaminar stresses along the hole edge at different
interfaces under uniaxial extension are investigated. According to the symmetries of the structure and loading, a suitable
finite-element model is developed. Utilizing a three-dimensional elastic-plastic finite-element procedure elaborated previously,
a finite-element modeling of the interlaminar stresses in a thick angle-ply composite laminate is carried out. Based on the
interlaminar stresses obtained, the dangerous locations of delamination initiation are predicted. The results obtained indicate
that there is some relationship between the dangerous locations and fiber orientations in the adjacent layers, and it maybe
inferred that the critical locations are near the regions where the hole edge is tangent to the fiber orientation in the layers
adjacent to the interface. The interlaminar stresses at the same interfaces are not sensible to distances from the midplane
of the laminate. Very high interlaminar tensile stresses are found to exist on the hole edge at the +25°/+25° or –25°/–25°
interfaces, and delaminations can initiate there first.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 427-440, May-June, 2009. 相似文献
4.
R. Rikards F. -G. Buchholz A. K. Bledzki G. Wacker A. Korjakin 《Mechanics of Composite Materials》1996,32(5):439-462
The interlaminar fracture behavior of unidirectional glass fiber reinforced composites with fiber surface treatment has been investigated in modes I and II and for fixed mode I to mode II ratio of 1.33. The data obtained from these tests have been analyzed by using different analytical approaches. The present investigation is focused on the influence of the glass fiber surface treatment on the interlaminar fracture toughness of unidirectional laminates. Glass fibers with two different fiber surface treatments have been investigated. fiber surface treatment was carried out by using a polyethylene or silane coupling agent in combination with modifying agents. The glass fibers were embedded in the brittle epoxy matrix. Mode I, mode II, and mixed-mode I/II tests were performed in order to determine critical strain energy release rates. Double cantilever beam (DCB), end-notched flexure (ENF), and mixed-mode flexure (MMF) specimens were used. For both types of fiber surface treatment about the same values of mode I initiation fracture toughness GIC init were obtained. It was observed that in mode I interlaminar crack growth in the DCB test for the composite sized by polyethylene, the crack propagation is accompanied by extensive fiber bridging. For both fiber surface treatments interlaminar fracture toughness increases considerably with increasing of crack length. For the fiber surface treatment with the silane coupling agent, the value of mode II initiation fracture toughness GIIC init was about 2.5-times higher in comparison with that of a composite sized by polyethylene. For both types of fiber surface treatments the mixed-mode I/II test has shown a similar behavior to the mode I DCB test. 相似文献
5.
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
6.
Interlaminar Crack Propagation Analysis of ENF Specimens Based on the Cohesive Zone Model北大核心CSCD
下载免费PDF全文
![点击此处可从《应用数学和力学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Based on the classical laminated plate theory and the cohesive zone model, a theoretical model for general delamination cracked laminates was established for crack propagation of pure mode Ⅱ ENF specimens. Compared with the conventional beam theory, the proposed model fully considered the softening process of the cohesive zone and introduced the nonlinear behavior of ENF specimens before failure. The predicted failure load is smaller than that under the beam theory and closer to the experimental data in literatures. Compared with the beam theory with only fracture toughness considered, the proposed model can simultaneously analyze the influences of the interface strength, the fracture toughness and the initial interface stiffness on the load-displacement curves in ENF tests. The results show that, the interface strength mainly affects the mechanical behavior of specimens before failure, but has no influence on crack propagation. The fracture toughness is the main parameter affecting crack propagation, and the initial interface stiffness only affects the linear elastic loading stage. The cohesive zone length increases with the fracture toughness and decreases with the interface strength. The effect of the interface strength on the cohesive zone length is more obvious than that of the fracture toughness. When the adhesive zone tip reaches the half length of the specimen, the adhesive zone length will decrease to a certain extent. Copyright ©2022 Applied Mathematics and Mechanics. All rights reserved. 相似文献
7.
Zhang Shu-hui Liang Guo-zheng Zhang Wei Zeng Jin-fang 《Mechanics of Composite Materials》2006,42(6):507-512
The surface of aramid fibers was modified with a polymer coating — a surface treatment reagent containing epoxy resin. The
resulting fibers were examined by using NOL tests, hydroburst tests, and the scanning electron microscopy. The modified fibers
had a rougher surface than the untreated ones. The interlaminar shear strength of an aramid-fiber-reinforced epoxy composite
was highest when the concentration of polymer coating system was 5%. The translation of fiber strength in an aramid/epoxy
composite vessel was improved by 8%. The mechanism of the surface treatment of fibers in improving the mechanical properties
of aramid/epoxy composites is discussed.
Russian translation publeshed in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 729–738, November–December, 2006. 相似文献
8.
Junjie Ye Xuefeng Chen Zhi Zhai Bing Li Yugang Duan Zhengjia He 《Mechanics of Composite Materials》2010,46(4):405-416
This paper aims to investigate the effect of microstructure parameters (such as the cross-sectional shape of fibers and fiber
volume fraction) on the stress–strain behavior of unidirectional composites subjected to off-axis loadings. A micromechanical
model with a periodic microstructure is used to analyze a representative volume element. The fiber is linearly elastic, but
the matrix is nonlinear. The Bodner–Partom model is used to characterize the nonlinear response of the fiber-reinforced composites.
The analytical results obtained show that the flow stress of composites with square fibers is higher than with circular or
elliptic ones. The difference in the elastoplastic response, which is affected by the fiber shape, can be disregarded if the
fiber volume fraction is smaller than 0.15. Furthermore, the effect of fiber shape on the stress–strain behavior of the composite
can be ignored if the off-axis loading angle is smaller than 30°. 相似文献
9.
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
10.
The generalized independent set (GIS) problem was first introduced by Hochbaum and Pathria (Forest Sci 43(4), 544–554, 1997) and independently explored in greater detail by Hochbaum (Manage Sci 50(6), 709–123, 2004). This problem, with applications in forest management and a variety of related areas, is a generalization of the classical maximum independent set problem. In this paper we highlight a natural, nonlinear formulation for the problem that is an attractive alternative to the linear model found in the literature. The effectiveness of this alternative formulation is demonstrated by computational experience on test problems of varying size and density, disclosing a dramatic reduction in the time to obtain optimal and near optimal solutions and an ability to solve much larger problems. 相似文献
11.
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
12.
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
13.
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
14.
The tensile strength and the fracture properties of advanced SiC-based fibers were characterized, and an extensive fractographic
analysis was conducted to correlate their mechanical behavior and microstructure. Tensile tests re vealed that the strength
of Hi-Nicalon™ and Hi-Nicalon™ Type S fibers was sensitive to a critical flaw. The inspection of fracture surfaces revealed
that the fracture of these fibers originated mainly at the critical flaw, which was surrounded by an obvious mirror zone.
The Tyranno™-SA fiber showed a transcrystalline fracture behavior. The different fracture behavior observed in this work could
be related to different fabrication processes and compositions at the grain boundary. For the Hi-Nicalon™ and Hi-Nicalon™
Type S fibers, the critical flaw size was linearly related to the mirror size. By using the linear fracture mechanics, the
fracture toughness and the critical fracture energy of the fibers were estimated.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 759–770, November–December, 2006. 相似文献
15.
O. G. Gurtovyi 《Mechanics of Composite Materials》2000,36(3):193-198
A phenomenological yield condition for quasi-brittle and plastic orthotropic materials with initial stresses is suggested.
All components of the yield tensor are determined from experiments on uniaxial loading. The reliability estimates of the criterion
suggested is discussed. For a plastic material without initial stresses, the given condition transforms into the Marin—Hu
criterion. The defining equations of the deformation theory of plasticity with isotropic and “anisotropic” hardening, associated
with the yield condition suggested, are obtained. These equations are used as the basis for a highly accurate nonclassical
continuous model for nonlinear deformation of thick sandwich plates. The approximations with respect to the transverse coordinate
take into account the flexural and nonflexural deformations in transverse shear and compression. The high-order approximations
allow us to model the occurrence of layer delamination cracks by introducing thin nonrigid interlayers without violating the
continuity concept of the theory.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. pp. 329–340, May–June, 2000. 相似文献
16.
Measuring and modeling the thermal conductivities of three-dimensionally woven fabric composites 总被引:1,自引:0,他引:1
The effect of a three-dimensional fiber reinforcement on the out-of-plane thermal conductivity of composite materials is investigated.
Composite preforms with different fibers in the thickness direction were fabricated. After in fusion by using a vacuum-assisted
resin transfer molding process, their through-thickness thermal conductivities were evaluated. The measured thermal conductivities
showed a significant increase compared with those of a typical laminated composite. Although the through-thickness thermal
conductivity of the samples increased with through-thickness fiber volume fraction, its values did not match those predicted
by the simple rule of mixtures. By using finite-element models to better under stand the behavior of the composite material,
improvements in an existing analytical model were performed to predict the effective thermal conductivity as a function of
material properties and in-contact thermal properties of the composite.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 241–254, March–April, 2009. 相似文献
17.
Yoichi Mieda 《Mathematische Zeitschrift》2007,257(2):403-425
In this paper, we discuss a p-adic analogue of the Picard–Lefschetz formula. For a family with ordinary double points over a complete discrete valuation
ring of mixed characteristic (0,p), we construct vanishing cycle modules which measure the difference between the rigid cohomology groups of the special fiber
and the de Rham cohomology groups of the generic fiber. Furthermore, the monodromy operators on the de Rham cohomology groups
of the generic fiber are described by the canonical generators of the vanishing cycle modules in the same way as in the case
of the ℓ-adic (or classical) Picard–Lefschetz formula. For the construction and the proof, we use the logarithmic de Rham–Witt
complexes and those weight filtrations investigated by Mokrane (Duke Math. J. 72(2):301–337, 1993).
相似文献
18.
A three-dimensional representative volume-element model is presented to study the micromechanical behavior of woven-fabric
composites. The effects of the fiber undulation zone and the fiber braid angle on the elastic modulus of the composites are
taken into account in the unit cell. Based on isostrain and isostress assumptions, a standard homogenization procedure is
used to calculate the effective elastic properties of woven-fabric composites, and all the final stiffness components are
expressed in an explicit form. The results obtained by the model considered agree with published experimental results very
well. The relationship between the geometric parameters, such as fiber width, thickness, volume fraction, etc., and the macromechanical
behavior of the composites can be obtained by this model.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 209–220, April–May, 2006. 相似文献
19.
Based on the weakest-link model, a family of fiber strength distributions is investigated assuming a two-stage failure process.
At the first stage, a weakest link is formed (instantly or gradually), but at the second one the fracture of this link takes
place. The gradual accumulation of flaws is described with the aid of Markov chain theory. The adequacy of the models considered
is verified by checking them against experimental strength data for E-glass and flax fibers of various lengths. It is found
that the models are not less accurate, but are even better, in a number of cases, than the model based on the known modified
Weibull model with a power-law relation between the fiber length and the scale parameter.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 179–192, March–April, 2006. 相似文献
20.
Analysis of the fiber length dependence of its strength by using the weakest-link approach 2. Analysis of test data 总被引:1,自引:0,他引:1
A method for estimating the model parameters is described, the results found in processing glass, flax, and carbon fiber and
carbon bundle datasets are reported, and a comparison of different models is given.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 65–74, January–February, 2008. 相似文献