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1.
Effect of moisture absorption on the micromechanical behavior of carbon fiber/epoxy matrix composites 总被引:1,自引:0,他引:1
J. I. Cauich-Cupul E. Pérez-Pacheco A. Valadez-González P. J. Herrera-Franco 《Journal of Materials Science》2011,46(20):6664-6672
Carbon fiber/epoxy material in the form of a single fiber unidirectional composite was subjected to controlled humidity environments.
Moisture uptake in polymer composites has significant effects on the mechanical properties of the matrix as well as on the
final performance of the composite material. Diminishing of the mechanical properties of the matrix is attributed to a decrease
of its glass transition temperature (T
g). The quality of the fiber–matrix interphase was assessed using the single fiber fragmentation test and the fiber-fragment
length, considered as an indicator of interfacial quality. In order to measure the fiber fragment lengths and indentify failure
mechanism at the interface optical observation and acoustic emission technique were used. The speed of propagation of an acoustic
wave in the material was also determined. A comparison is made of interfacial shear strength values determined by acoustic
emission and optical techniques. Excellent agreement between the two techniques was obtained. By means of a micromechanical
model, it was possible to determine from the fragmentation lengths a measure of the interfacial shear strength between the
fiber and the matrix. The role of moisture uptake swelling of the matrix on the residual stresses is considered to be important
when considering the effect deterioration of interfacial shear properties. Both the contribution of the radial stresses and
the mechanical component of fiber–matrix adhesion are seen to decrease rapidly for higher moisture contents in the matrix
and/or interface. 相似文献
2.
The cruciform specimen geometry has recently been established to investigate the transverse tensile behavior of single-fiber or multiple-fiber titanium matrix composites; however, the results on only relatively few commercially-available fibers have been reported to date. The present study reports the transverse behavior of a range of SiC fibers prepared by different manufacturers and with different surface coatings. The mechanical response of the composite and the damage present at the interfacial region have been documented. In general, the stress–strain behavior was found to be sensitive to the chemical and structural nature of the fiber–matrix interfacial region. Fibers with carbon-rich coatings were found to have a range of interfacial strengths depending on the structure of the interface layers, while uncoated fiber interfaces have a high strength. This study demonstrates the value of the single-fiber transverse cruciform test for quantitatively comparing the behavior of various fibers and coatings, and shows that it can be useful for coating development studies. 相似文献
3.
Sudhir Tiwari Mohit Sharma Stephane Panier Brigitte Mutel Peter Mitschang Jayashree Bijwe 《Journal of Materials Science》2011,46(4):964-974
The parameters controlling performance of a fiber-reinforced polymer composite are type of matrix and fibers, their amount,
aspect ratio, fiber orientation with respect to loading direction, fiber–matrix interface, and processing technique. In the
case of carbon fiber reinforcement, fiber–matrix interface has always been a serious concern, because of chemical inertness
of carbon fibers toward matrix and hence efforts are continued to enhance the fiber–matrix adhesion. A recent technique of
cold remote nitrogen oxygen plasma was employed for surface treatment of carbon fabric (CF) to enhance its chemical reactivity
and mechanical interaction toward matrix material. Untreated and plasma treated CF were used as bidirectional reinforcement
for developing high performance composites with various specialty polymer matrices such as Polyetherimide, Polyethersulfone,
and Polyetheretherketone. Treated CF reinforced composites showed appreciable improvement in most of the mechanical properties,
which varied with type of plasma, its dozing and matrix used. X-ray Photoelectron Spectroscopy confirmed improvement in O/C
and N/C ratio indicating inclusion of Oxygen and Nitrogen on the surfaces of fibers due to plasma treatment, which was responsible
for enhanced adhesion. Similarly, Fourier Transform Infrared–Attenuated Total Reflectance Spectroscopy indicated presence
of ether, carboxylic, and carbonyl functional groups on the plasma-treated surface of fibers. Raman spectroscopy indicated
slight distortion in graphitic structure of treated CF. Scanning Electron Microscopy also indicated changes in the topography
of treated CF, indicating enhanced mechanical interlocking with matrix. 相似文献
4.
Determination of interface properties from experiments on the fragmentation process in single-fiber composites 总被引:1,自引:0,他引:1
This paper attempts to quantify the fracture properties (strength and toughness) of the fiber–matrix interface in composites, using the fragmentation process and debonding growth for HI-Nicalon™ SiC single-fiber and T300 carbon single-fiber epoxy (Bisphenol-A type epoxy resin with triethylenetetramine (TETA) as curing agent) composite systems. This method is based on the numerical modeling for the microscopic damage and fragmentation process in single-fiber composite (SFC) tests, with a cohesive zone model (CZM). For the HI-Nicalon™ SiC single-fiber epoxy composite in which the major damage near a fiber break is interfacial debonding, interface properties were reasonably determined as (TII,max, GIIc) = (75 MPa, 200 J/m2). In contrast, for T300 carbon single-fiber epoxy composite, we could not determine unique interfacial properties, since the variation of the cohesive parameters hardly affects the microscopic damage process due to the transition to the damage pattern dominated by matrix cracking. 相似文献
5.
Thermal residual stress is one of the major factors affecting composite mechanical performance. In this paper, a 3-D FEA technique
was utilized to analyze the thermal residual stress distribution in Carbon fiber/PPESK composite. Parabolic failure criterion
was used to predict composite potential failure zone. Results indicate that, thermal residual stress distributions in different
parts of the composite are different. At composite free end zone, the maximum thermal residual stress is located at fiber
surface; in composite inner zone, the maximum stress is located in the matrix; at composite defect zone, stress concentration
is located at defect surface. Thermal residual stress at composite free end zone will lead to fiber–matrix interfacial de-bonding.
Thermal residual stress concentration at composite defect zone will decrease composite mechanical performance. 相似文献
6.
Noa Lachman Hui Qian Matthieu Houllé Julien Amadou Milo S. P. Shaffer H. Daniel Wagner 《Journal of Materials Science》2013,48(16):5590-5595
Growing carbon nanotubes (CNTs) on the surface of fibers has the potential to modify fiber–matrix interfacial adhesion, enhance composite delamination resistance, and possibly improve toughness. In the present study, aligned CNTs were grown upon carbon fabric via chemical vapor deposition. Continuously monitored single-fiber composite fragmentation tests were performed on pristine and CNT-grafted fibers embedded in epoxy, and single-laminate compact-tension specimens were tested for fracture behavior. A significant increase (up to 20 %) was observed in the interfacial adhesion, at the cost of a decrease in the fiber tensile strength. As a result, the maximum load of the composite was decreased, but its residual load-bearing capacity more than doubled. The likely sources of these effects are discussed, as well as their implications. 相似文献
7.
This paper describes mechanism-based modeling of damage evolution in high temperature polymer matrix composites (HTPMC) under
thermo-oxidative aging conditions. Specifically, a multi-scale model based on micro-mechanics analysis in conjunction with
continuum damage mechanics (CDM) is developed to simulate the accelerated fiber–matrix debond growth in the longitudinal direction
of a unidirectional HTPMC. Using this approach, one can relate the behavior of composites at the micro-level (representative
volume element) to the macro-level (structural element) in a computationally tractable manner. Thermo-oxidative aging is simulated
with diffusion-reaction model in which temperature, oxygen concentration, and weight loss effects are considered. For debond
growth simulation, a model based on Darcy’s laws for oxygen permeation in the fiber–matrix interface is employed, that, when
coupled with polymer shrinkage, provides a mechanism for permeation-controlled debond growth in HTPMC. Benchmark of model
prediction with experimental observations of oxidation layer growth is presented, together with a laminate thermo-oxidative
life prediction model based on CDM to demonstrate proof-of-concept. 相似文献
8.
Effect of colloidal silica on the strength and energy absorption of glass fiber/epoxy interphases 总被引:1,自引:0,他引:1
Prior research has demonstrated that fiber-sizings can be designed to yield composite materials that simultaneously possess high energy absorption and structural properties. The improved mechanical properties resulted from control of the fiber surface chemistry and nano-scale topological features within the fiber–matrix interphase. The present study further explains the role of sizing chemistry and surface roughness on composite material performance. Model and commercial glass fiber epoxy specimens were fabricated using these fiber sizing systems resulting in interphase regions with varied surface topology and chemical functionality. Micromechanical measurements were performed using the microdroplet adhesion test method to quantify the fiber–matrix interfacial properties. Improvement in energy absorption and interfacial shear strength due to the presence of the nano-scale silica were quantified. Inspection of the failure modes revealed that the existence of colloidal silica promotes crack propagation along a more tortuous path within the interphase that results in progressive failure and contributes to increased energy dissipation. 相似文献
9.
单纤维拔出方法表征CFRP界面强度的研究 总被引:3,自引:0,他引:3
提出了单根碳纤维从环氧树脂基体中拔出的一种简易方法,在国内首次实现了用该方法表征碳纤维增强树脂基复合材料(CFRP)界面粘合性能的技术。 相似文献
10.
This paper is concerned with the derivation of a micromechanics model of a new type of piezoelectric fiber reinforced composite
(PFRC) materials. A continuum mechanics approach is employed to determine the effective properties of these composites. The
piezoelectric fibers of these composites are considered to be electroded at the fiber–matrix interface such that the electric
fields in the fiber and matrix become equal in the direction transverse to the fiber direction. The model has been verified
with the existing models. The present model also predicts that the effective piezoelectric coefficient of these PFRC which
accounts for the actuating capability in the fiber direction due to the applied field in the direction transverse to the fiber
direction improves over the corresponding coefficient of the material of the piezoelectric fibers if the fiber volume fraction
exceeds a critical fiber volume fraction. 相似文献
11.
Based on the difference in melting points between polyamide 66 (PA66) fiber and polyamide 6 (PA6) matrix, all-polyamide composites
were fabricated under various processing conditions. In these all-polyamide composites, the reinforcement and matrix share
the same molecular structure unit (–CONH–(CH2)5–). Because of the chemical similarity of the two components, good bonding at the fiber/matrix interface could be expected.
Effects of processing temperature and cooling rate on the structure and physical properties of composites were investigated
by SEM, DMA, DSC analyses, and static tensile test. Fiber/matrix interface strength benefited from elevated processing temperature.
The static tensile results showed that the maximum of tensile strength was observed in the processing temperature range of
225–245 °C. At different cooling rates, crystallization temperature of PA6 in the composites was increased compared to the
pure PA6 because of the nucleation effect of PA66 fiber surface to the PA6 matrix. A study of the matrix microstructure in
a single fiber-polymer composite gave proof of the transcrystalline growth at the fiber–matrix interface, the reason behind
which was the similar chemical compositions and lattice structures between PA6 and PA66. 相似文献
12.
Effect of carbon nanotubes on the interfacial shear strength of T650 carbon fiber in an epoxy matrix
R.J. Sager P.J. Klein D.C. Lagoudas Q. Zhang J. Liu L. Dai J.W. Baur 《Composites Science and Technology》2009,69(7-8):898-904
The interfacial shear strength of carbon nanotube coated carbon fibers in epoxy was studied using the single-fiber composite fragmentation test. The carbon fibers were coated with carbon nanotubes (CNT) on the fiber surface using thermal chemical vapor deposition (CVD). The CVD process was adjusted to produce two CNT morphologies for the study: radially aligned and randomly oriented. The purpose of the CNT coating was to potentially produce a multifunctional structural composite. Results of the single-fiber fragmentation tests indicate an improvement in interfacial shear strength with the addition of a nanotube coating. This improvement can most likely be attributed to an increase in the interphase yield strength as well as an improvement in interfacial adhesion due to the presence of the nanotubes. 相似文献
13.
利用光弹性实验和有限元计算两种方法对单丝拔出复合材料模型的界面剪应力进行了研究。从计算和实验两个方面证明,当在纤维自由端施加一轴向拉力后,在单丝与基体界面的埋入端附近将出现剪应力的最大值。然后,沿着单丝的埋入方向,剪应力迅速降低,在界面区的中间趋于最小值,并且基本稳定不变。由此证明,单丝增强复合材料中界面的应力传递主要集中在单丝的埋入端附近,并且在这一区域最先达到危险应力,发生界面的脱胶破坏,引起整个试件的失效。 相似文献
14.
Taner Yilmaz 《Journal of Materials Science》2010,45(9):2381-2389
The influence of annealing duration on the erosive wear behavior of short glass fiber (40% w/w) and CaCO3 mineral particulate (25% w/w)–short glass fiber (40% w/w) (total: 65% w/w) reinforced PPS composites has been characterized
under various experimental conditions by differential scanning calorimetry (DSC) and erosion measurements. The erosive wear
of the composites have been evaluated at different impingement angles (30, 45, 60, and 90°) and at four different annealing
periods (30, 60, 90, and 120 min). Increase in the total crystallization causes an improvement in the erosive wear properties
of the samples. Annealing time controls the morphology by influencing the degree of crystallinity in the matrix and in the
fiber–matrix interface. This formation restricts fiber–matrix debonding. There is no linear proportionality between annealing
time and relative degree of crystallization. The results indicate that PPS composites show maximum in wear versus impact angle
relation at 60° confirming their semi-ductile failure behavior. The morphologies of eroded surface are examined by the scanning
electron microscope. 相似文献
15.
In this study, a micromechanical model is presented to study the combined normal, shear and thermal loading of unidirectional
(UD) fiber reinforced composites. An appropriate truly meshless method based on the integral form of equilibrium equations
is also developed. This meshless method formulated for the generalized plane strain assumption and employed for solution of
the governing partial differential equations of the problem. The solution domain includes a representative volume element
(RVE) consists of a fiber surrounded by corresponding matrix in a square array arrangement. A direct interpolation method
is employed to enforce the appropriate periodic boundary conditions for the combined thermal, transverse shear and normal
loading. The fully bonded fiber–matrix interface condition is considered and the displacement continuity and traction reciprocity
are imposed to the fiber–matrix interface. Predictions show excellent agreement with the available experimental, analytical
and finite element studies. Comparison of the CPU time between presented method and the conventional meshless local Petrov–Galerkin
(MLPG) shows significant reduction of the computational time. The results of this study also revealed that the presented model
could provide highly accurate predictions with relatively small number of nodes and less computational time without the complexity
of mesh generation. 相似文献
16.
Raman spectroscopy was used to study the stress relaxation in broken fibers in a unidirectional composite. A single-fiber model composite consisting of a high modulus PAN-based carbon fiber and an epoxy resin matrix was loaded incrementally until the fiber got broken.Then the stress profile in the broken fiber was monitored under constant overall strain for 1000 hours by determining fiber stress through the stress dependence of the 2700 cm–1 Raman band peak position. Three experiments were done at different overall strains.It was observed that the stress profile in each broken fiber changed only a little even after 1000 hours whereas matrix normal stress in the fiber direction relaxed to about a quarter of the initial value in about 200 hours. It is shown that this result does not support linear viscoelastic solutions based on perfect bonding at interface since the present experiments had interfacial debonding and matrix shear yielding around fiber breaks. 相似文献
17.
C. Wretfors S.-W. Cho R. Kuktaite M. S. Hedenqvist S. Marttila S. Nimmermark E. Johansson 《Journal of Materials Science》2010,45(15):4196-4205
Wheat gluten (WG) is a promising base material for production of “green” plastics, although reinforcement is needed in more
demanding applications. Hemp fiber is a promising reinforcement source but difficulties exist in obtaining desired properties
with a WG-based matrix. This study aimed at improving fiber dispersion and fiber–matrix interactions using a high speed blender
and a diamine as a cross-linker. Samples were manufactured using compression molding, two types of blenders and addition of
diamine. Mechanical properties were assessed with tensile testing. Tensile-fractured surfaces were examined with scanning
electron microscopy (SEM). Protein polymerization and fiber–protein matrix interactions were examined using high performance
liquid chromatography (HPLC) and confocal laser scanning microscopy (CLSM). The results showed that a higher-speed grinding
yielded a more even distribution of fibers and a more polymerized protein structure compared to a lower-speed grinding. However,
these improvements did not result in increased strength, stiffness, and extensibility for the higher-speed grinding. The strength
was increased when the grinding was combined with addition of a diamine (Jeffamine? EDR-176). HPLC, SEM, and CLSM, indicated that diamine added samples showed a more “plastic” appearance together with a stiffer
and stronger structure with less cracking compared to samples without diamine. The use of the diamine also led to an increased
polymerization of the proteins, although no effect on the fiber–protein matrix interactions was observed using microscopical
techniques. Thus, for future successful use of hemp fibers to reinforce gluten materials, an appropriate method to increase
the fiber–protein matrix interaction is needed. 相似文献
18.
19.
Biocomposite fiber has been developed from wood pulp and polypropylene (PP) by an extrusion process and the generated biocomposite
fibers were characterized to understand the nature of interaction between wood pulp reinforcement and PP matrix. The use of
maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Fiber length analysis
showed that most of the fiber lengths lie within the range of 0.2–1.0 mm. Changes in absorption peaks were observed in Fourier
transform infrared spectroscopy of biocomposite fibers as compared to the virgin wood pulp, which indicated possible chemical
linkages between the fiber and polymer matrix. SEM study was carried out to observe fiber–matrix adhesion at the interface
within the composite and MAPP treatment was found to be effective in increasing reinforcing fibers–matrix compatibility. X-ray
computed tomography was conducted to understand the internal architecture of the biocomposite fiber and the results showed
that with incorporation of additional wood pulp content, the fiber becomes more aligned along length axis possibly due to
compression and die geometry of the extruder. 相似文献
20.
以硅烷偶联剂和正硅酸乙酯(TEOS)为前躯体, 以固体酸-对甲苯磺酸为催化剂制备硅溶胶, 利用硅溶胶对碳纤维进行表面改性后, 以环氧树脂为基体, 制备碳纤维增强环氧树脂复合材料。利用SEM、 TEM、 万能试验机、 偏光显微镜等对表面改性前后的碳纤维形态、 力学性能及碳纤维/环氧树脂复合材料的界面性能进行表征, 研究了硅溶胶改性碳纤维对其复合材料界面性能影响。结果表明, 硅溶胶处理碳纤维后, 在碳纤维表面原位生成具有膜-粒结构的表面层, 改性后碳纤维的强度由2.41 GPa提高到3.00 GPa, 界面性能也得到了明显改善, 界面剪切强度(IFSS)提高了51.41%。 相似文献