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This study aims to investigate the thermal conductivity and the linear coefficient of thermal expansion for short fibre reinforced composites. The study combines numerical and statistical analyses in order to primarily examine the representative size and the effective properties of the volume element. Effects of various micromechanical parameters, such as fibre’s aspect ratio and fibre’s orientation, on the minimum representative size are discussed. The numerically acquired effective properties, obtained for the representative size, are presented and compared with analytical models. 相似文献
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The effects of interphase between fibers and matrix on the micro-and macro-mechanical behaviors of fiber-reinforced composite
lamina subjected to transverse shear load at remote distance have been studied. The interphase has been modeled by the compliant
spring-layers that are linearly related to the normal and tangential tractions. Numerical analyses on composite basic cells
have been carried out using the boundary element method. For undamaged composites the micro-level stresses at the matrix side
of the interphase and effective shear modulus have been calculated as a function of the fiber volume fraction and the interphase
stiffness. Results are presented for various interphase stiffnesses from perfect bonding to total debonding. For a square
array composite results show that for a high interphase stiffness k > 10, an increase in a fiber volume fraction results in a higher effective transverse shear modulus. For a relatively low
interphase stiffness k < 1, it is shown that an increase in the fiber volume fraction causes a decrease in the effective transverse shear modulus.
For perfect bonding, the effective shear modulus for a hexagonal array composite is slightly larger than that for a square
array composite. Also for the damaged composite with partially debonded interphase, local stress fields and effective shear
moduli are calculated and a decrease in the effective shear modulus has been observed. 相似文献
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The micromechanical behaviour of Al2O3 short fibre reinforced Al-5.5Zn matrix composite has been in-situ studied by using TEM. The results show that in the composite the nucleation and propagation of cracks take place mainly in the matrix, as well as in the region near the fibre/matrix interface. It has been also observed that the microcracks can close during unloading.So the fracture property can be characterized by crack open displacement (COD). The cracking characteristic may result from the large strength difference between the matrix and fibre. 相似文献
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Abstract An analytical approach is developed to obtain the solution of coupled Schrödinger equations for polarization components of a solitary wave. Variational analysis allows us to describe optical pulse propagation in fibres with nonlinear birefringence. Conditions for polarization channel switching and locking are formulated. 相似文献
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A kind of diamond grinding wheel bonded by short cast iron fibres has been developed. ln comparison with high quality bronze bonded diamond grinding wheel. the new wheel was more suitable to grind hard and brittle materials like ceramics. For Si3N4, the grinding efficiency has been raised two times and the grinding ratio five times 相似文献
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A simple analytical impact damage model for preliminary design analysis is developed on the basis of experimental findings observed from quasi-static lateral load and low velocity impact tests. The analytical model uses a non-linear approximation method (Rayleigh–Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point load at its centre. It is assumed that the deformation due to a static transverse load is similar to that occurred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with finite element (FE) predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture model developed by the second investigator to estimate the compression after impact strength of such laminates. This approach could save significant running time when compared to FE numerical solutions.
Corresponding author. 相似文献
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Impact Resistance of Short Fibre/Particle Reinforced Epoxy 总被引:1,自引:0,他引:1
The influence of temperature on the fracture behaviour of epoxy-based composites was studied using an instrumented Charpy impact approach. A series of epoxy reinforced with short carbon fibres (SCF) and additionally filled with various amounts of PTFE and graphite particles was considered in this study. Unnotched specimens were tested at –196°C, 20°C, and 70°C, respectively. It was found that, for specimens with the same matrix content, a proper hybridisation of composites was possible to achieve a better impact performance compared to single-filler/epoxy. For example, 10 vol.%PTFE+10 vol.%SCF/epoxy exhibited a higher impact resistance than that of 20 vol.%SCF/epoxy at all measured temperatures. Failure mechanisms at different temperatures were discussed with SEM fractography. 相似文献
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Jute fibre reinforced polyester composites were developed and characterized for friction and sliding wear properties. Effect
of fibre orientation and applied load on tribological behaviour of jute fibre reinforced polyester composites were determined.
It is found that wear resistance was maximum in TT sample, where fibres were normal to sliding direction. Wear rate under
sliding mode follows this trend; WTT < WLT <WLL LL sample showed higher capability to sustain the load whereas lowest wear resistance found in this case. The coefficient
of friction found highest for TT sample and lowest for LT sample. The coefficient of friction decreased with increase of applied
load. Worn surfaces were analysed and discussed with the help of SEM. 相似文献
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Nickel,as the carrier through which Fe atomsdiffuse,obviously enhances the densification ofsintered compact containing short cast iron fibre.When Ni content is above 4.5 wt-% there are someaustenites in microstructure at room temperature,discontinuous cementite networks at the interfacesbetween austenites and pearlites,free graphite pre-cipitated in austenite and pores andWidmannst(?)tten carbide precipitated in austenite.When Ni content is about 12 wt-%,it leads to de-crease in densification ratio and change in fracturemorphology of sintered compact from ductile tobrittle. 相似文献
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Garth M. Pearce Alastair F. Johnson Rodney S. Thomson Donald W. Kelly 《Applied Composite Materials》2010,17(3):329-346
This paper reports on recent experimental work to investigate the response of bolted carbon fibre composite joints and structures
when subjected to constant dynamic loading rates between 0.1 m/s and 10 m/s. Single fastener joints were tested in both the
bearing (shear) and pull-through (normal) loading directions. It was found that the joints exhibited only minor loading rate
dependence when loaded in the pull-through direction but there was a significant change in failure mode when the joints were
loaded in bearing at or above 1 m/s. Below 1 m/s loading rate the failure mode consisted of initial bolt bearing followed
by bolt failure. At a loading rate of 1 m/s and above the bolt failed in a ‘tearing’ mode that absorbed significantly more
energy than the low rate tests. A simple composite structure was created to investigate the effect of loading rate on a more
complex joint arrangement. The structure was loaded in two different modes and at constant dynamic loading rates between 0.1 m/s
and 10 m/s. For the structure investigated and the loading modes considered, only minor loading rate effects were observed,
even when the dominant contribution to joint loads came from bearing. It was observed that the load realignment present in
the structural tests allowed the joints to fail in a mode that was not bearing dominant, and hence the loading rate sensitivity
was not expressed. 相似文献
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P. M. SISNEROS P. YANG R. F. EL‐HAJJAR 《Fatigue & Fracture of Engineering Materials & Structures》2012,35(7):672-682
The use of carbon fibre‐based polymeric composites in bicycle components has dramatically increased in the last few decades. This paper presents the results of fatigue and impact testing on bicycle forks that are known to have quality‐related manufacturing defects. In the investigation performed, acoustic emission testing is used to monitor crack growth during fatigue loading and impact. The results show three distinct stages in composite fatigue failure related to initiation, propagation and final growth. Implications of the results on design and testing of composite bicycle components are addressed pointing to a greater need in understanding current design procedures. 相似文献
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Most developments in the area of natural fibre reinforced composites have focused on random discontinuous fibre composite systems. The development of continuous fibre reinforced composites is, however, essential for manufacturing materials, which can be used in load-bearing/structural applications. The current work aims to develop high-performance natural fibre composite systems for structural applications using continuous textile reinforcements like UD-tapes or woven fabrics. One of the main problems in this case is the optimisation of the yarn to be used to manufacture the textile reinforcement. Low twisted yarns display a very low strength when tested dry in air and therefore they cannot be used in processes such as pultrusion or textile manufacturing routes. On the other hand, by increasing the level of twist, a degradation of the mechanical properties is observed in impregnated yarns (e.g., unidirectional composites) similar to off-axis composites. Therefore, an optimum twist should be used to balance processability and mechanical properties. Subsequently, different types of fabrics (i.e., biaxial plain weaves, unidirectional fabrics and non-crimp fabrics) were produced and evaluated as reinforcement in composites manufactured by well established manufacturing techniques such as hand lay-up, vacuum infusion, pultrusion and resin transfer moulding (RTM). Clearly, as expected, the developed materials cannot directly compete in terms of strength with glass fibre composites. However, they are clearly able to compete with these materials in terms of stiffness, especially if the low density of flax is taken into account. Their properties are however very favourable when compared with non-woven glass composites. 相似文献
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In the present work residual stresses in a boron fibre/aluminium matrix composite are determined through an etching method. The inhomogeneous removal of surface layers, due to the different sensitivity of boron and aluminium to alkaline environment, requires the application of a modified technique for the estimation of deformations and the calculation of stresses. The results obtained indicate considerable deviations in both distribution and magnitude of residual stresses in the same MMC, due to different fabrication methods.
N. P. Andrianopoulos: Corresponding author. 相似文献
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Acoustic emission (AE) peak amplitude and cumulative energy emitted during 50% of failure of composite specimen was collected, analyzed, and utilized to predict the ultimate tensile strength (UTS) using artificial neural network (ANN) and the performance of various training algorithm on prediction was analyzed. AE data have been collected from finite numbers of randomly oriented short glass fiber-epoxy tensile specimens, while loading up to failure in a tensile testing machine. AE response from each of the specimen was classified and segregated by understanding the failure mechanism. A feed forward back-propagation type ANN was designed and the segregated data of amplitude hits and cumulative energy was processed using two separate networks to predict the UTS of corresponding specimens using it with appropriate parameters and the results were analyzed. 相似文献