The Effect of Material and Geometrical Uncertainty on the Homogenized Properties of Graphene Sheet-Reinforced Composites

2019 ◽  
Vol 5 (3) ◽  
Author(s):  
Dimitrios Savvas ◽  
George Stefanou
Keyword(s):  
Graphene Sheet ◽  
Relative Effect ◽  
Statistical Characteristics ◽  
Structural Defects ◽  
Reinforced Composites ◽  
Graphene Lattice ◽  
The Matrix ◽  
Dispersed Inclusions ◽  
Geometrical Uncertainty ◽  
Inclusion Material

This paper focuses on the computational homogenization of graphene sheet-reinforced composites with randomly dispersed inclusions and uncertainty in the constituent materials. Material uncertainty of the matrix and of the graphene inclusions are considered separately and their relative effect on the homogenized properties is assessed. The uncertainty in the inclusion material is due to structural defects of the graphene lattice and is taken into account using random variables for each component of the elasticity matrix. Moreover, Monte Carlo simulation is used to extract the statistical characteristics of the homogenized properties of the composite material. The results lead to useful conclusions regarding the effect of material and geometrical uncertainty on the macroscopic properties of graphene sheet-reinforced composites.

Phase identification in SiC whisker reinforced Al2O3-R2O3-based composites

1992 ◽  
Vol 50 (1) ◽  
pp. 152-153
Author(s):  
C.M. Sung ◽  
K.J. Ostreicher ◽  
M.L. Huckabee ◽  
S.T. Buljan
Keyword(s):  
Analytical Electron Microscopy ◽  
Phase Identification ◽  
Reinforced Composites ◽  
Ion Milling ◽  
X Ray ◽  
Binary Oxides ◽  
Analytical Electron ◽  
The Matrix ◽  
Second Phases ◽  
Convergent Beam

A series of binary oxides and SiC whisker reinforced composites both having a matrix composed of an α-(Al, R)2O3 solid solution (R: rare earth) have been studied by analytical electron microscopy (AEM). The mechanical properties of the composites as well as crystal structure, composition, and defects of both second phases and the matrix were investigated. The formation of various second phases, e.g. garnet, β-Alumina, or perovskite structures in the binary Al2O3-R2O3 and the ternary Al2O3-R2O3-SiC(w) systems are discussed.Sections of the materials having thicknesses of 100 μm - 300 μm were first diamond core drilled. The discs were then polished and dimpled. The final step was ion milling with Ar+ until breakthrough occurred. Samples prepared in this manner were then analyzed using the Philips EM400T AEM. The low-Z energy dispersive X-ray spectroscopy (EDXS) data were obtained and correlated with convergent beam electron diffraction (CBED) patterns to identify phase compositions and structures. The following EDXS parameters were maintained in the analyzed areas: accelerating voltage of 120 keV, sample tilt of 12° and 20% dead time.

Investigation of Fiber-Reinforced Modified Epoxy Resin Composites

2012 ◽  
Vol 510-511 ◽  
pp. 577-584 ◽  
Author(s):  
A. Quddos ◽  
Mohammad Bilal Khan ◽  
R.N. Khan ◽  
M.K.K. Ghauri
Keyword(s):  
Epoxy Resin ◽  
High Strength ◽  
Polymeric Matrix ◽  
Fiber Reinforced Composites ◽  
Resin Matrix ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Epoxy Resin Matrix ◽  
The Matrix ◽  
Modified Epoxy

The impregnation of the fiber with a resin system, the polymeric matrix with the interface needs to be properly cured so that the dimensional stability of the matrix and the composite is ensured. A modified epoxy resin matrix was obtained with a reactive toughening agent and anhydride as a curing agent. The mechanical properties of the modified epoxy matrix and its fiber reinforced composites were investigated systematically. The polymeric matrix possessed many good properties, including high strength, high elongation at break, low viscosity, long pot life at room temperature, and good water resistance. The special attentions are given to the matrix due to its low out gassing, low water absorption and radiation resistance. In addition, the fiber-reinforced composites showed a high strength conversion ratio of the fiber and good fatigue resistance. The dynamic and static of the composite material were studied by thermo gravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) with EDX. The influences of processing technique such as curing and proper mixing on the mechanical and interfacial properties were determined. The results demonstrated that the modified epoxy resin matrix is very suitable for applications in products fabricated with fiber-reinforced composites.

scholarly journals Welding thermal cycle-triggered precipitation processes in steel S700MC subjected to the thermo-mechanical control processing

2017 ◽  
Vol 62 (1) ◽  
pp. 321-326 ◽  
Author(s):  
J. Górka
Keyword(s):  
Thermomechanical Processing ◽  
Control Process ◽  
Base Material ◽  
Structural Defects ◽  
Accelerated Cooling ◽  
Internal Stresses ◽  
Mechanical Control ◽  
Thin Foils ◽  
Precipitation Processes ◽  
The Matrix

Abstract This study presents tests concerned with welding thermal process-induced precipitation processes taking place in 10 mm thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) with accelerated cooling. The thermomechanical processing of steel S700MC leads to its refinement, structural defects and solutioning with hardening constituents. Tests of thin foils performed using a transmission electron microscope revealed that the hardening of steel S700MC was primarily caused by dispersive (Ti,Nb)(C,N) precipitates (being between several and less than twenty nanometers in size). In arc welding, depending on a welding method and linear energy, an increase in the base material in the weld is accompanied by the increased concentration of hardening microagents in the weld. The longer the time when the base material remains in the liquid state, the greater the amount of microagents dissolved in the matrix. During cooling, such microagents can precipitate again or remain in the solution. An increase in welding linear energy is accompanied by an increase in the content of hardening phases dissolved in the matrix and, during cooling, by their another uncontrolled precipitation in the form of numerous fine-dispersive (Ti,Nb)(C,N) precipitates of several nm in size, leading to a dislocation density increase triggered by type 2 internal stresses.

Entropy estimation of the fragments of chest X-ray images

2021 ◽  
pp. 20-26
Author(s):  
Aleksei Aleksandrovich Rumyantsev ◽  
Farkhad Mansurovich Bikmuratov ◽  
Nikolai Pavlovich Pashin
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Binary Classification ◽  
Statistical Characteristics ◽  
Type I ◽  
Deep Convolutional Neural Networks ◽  
Preliminary Calculation ◽  
X Ray ◽  
The Matrix ◽  
Chest X Ray

The subject of this research is medical chest X-ray images. After fundamental pre-processing, the accumulated database of such images can be used for training deep convolutional neural networks that have become one of the most significant innovations in recent years. The trained network carries out preliminary binary classification of the incoming images and serve as an assistant to the radiotherapist. For this purpose, it is necessary to train the neural network to carefully minimize type I and type II errors. Possible approach towards improving the effectiveness of application of neural networks, by the criteria of reducing computational complexity and quality of image classification, is the auxiliary approaches: image pre-processing and preliminary calculation of entropy of the fragments. The article provides the algorithm for X-ray image pre-processing, its fragmentation, and calculation of the entropy of separate fragments. In the course of pre-processing, the region of lungs and spine is selected, which comprises approximately 30-40% of the entire image. Then the image is divided into the matrix of fragments, calculating the entropy of separate fragments in accordance with Shannon’s formula based pm the analysis of individual pixels. Determination of the rate of occurrence of each of the 255 colors allows calculating the total entropy. The use of entropy for detecting pathologies is based on the assumption that its values differ for separate fragments and overall picture of its distribution between the images with the norm and pathologies. The article analyzes the statistical values: standard deviation of error, dispersion. A fully connected neural network is used for determining the patterns in distribution of entropy and its statistical characteristics on various fragments of the chest X-ray image.

Process optimization for enhanced tribological properties of Al/MWCNT composites produced by powder metallurgy using artificial neural networks

2021 ◽  
Author(s):  
Turker Turkoglu ◽  
Sare Celik
Keyword(s):  
Powder Mixture ◽  
Pure Aluminum ◽  
Microstructural Analysis ◽  
Wear Test ◽  
Structural Defects ◽  
Wear Loss ◽  
Ann Model ◽  
Wear Properties ◽  
The Matrix ◽  
Artificial Neural

Abstract In order to eliminate the agglomeration problem of reinforcement in the nanocomposite, a two-step dispersion process was employed. Under ultra-sonication and ball milling, 1 wt.% of multi-walled carbon nanotubes (MWCNTs) were properly dispersed in pure aluminum (Al) (used as the matrix phase). The composite powder mixture was then consolidated in an inert Ar gas atmosphere by hot pressing under certain fabrication parameters. The powder mixture was characterized by Raman Spectroscopy, and it was found that MWCNTs did not cause structural defects in the pre-production process. The microstructural analysis of the sintered composites by scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDS), revealed that the reinforcement was uniformly distributed in the matrix. Wear test results indicated that the wear resistance of the composites increased with increase of MWCNT reinforcement, and the wear mechanism was determined to be a mixing type by examining the wear traces by SEM. In order to determine the effects of different process parameters on wear loss, a multilayer perceptron (MLP) based artificial neural network (ANN) was used, and experimental and predicted values were compared. It was noticed that the MLP based ANN model effectively evaluated the wear properties of the Al/MWCNT composites.

Fibre-Matrix Interface Development during High Temperature Exposition of Long Fibre Reinforced SiOC Matrix

2013 ◽  
Vol 592-593 ◽  
pp. 401-404
Author(s):  
Zdeněk Chlup ◽  
Martin Černý ◽  
Adam Strachota ◽  
Martina Halasova ◽  
Ivo Dlouhý
Keyword(s):  
High Temperature ◽  
Crack Formation ◽  
Fracture Behaviour ◽  
Point Of View ◽  
Reinforced Composites ◽  
Matrix Interface ◽  
Significant Damage ◽  
The Matrix ◽  
Fibre Matrix ◽  
Fibre Reinforced Composites

The fracture behaviour of long fibre reinforced composites is predetermined mainly by properties of fibre-matrix interface. The matrix prepared by pyrolysis of polysiloxane resin possesses ability to resist high temperatures without significant damage under oxidising atmosphere. The application is therefore limited by fibres and possible changes in the fibre matrix interface. The study of development of interface during high temperature exposition is the main aim of this contribution. Application of various techniques as FIB, GIS, TEM, XRD allowed to monitor microstructural changes in the interface of selected places without additional damage caused by preparation. Additionally, it was possible to obtain information about damage, the crack formation, caused by the heat treatment from the fracture mechanics point of view.

scholarly journals Tensile Characterizations of Oil Palm Empty Fruit Bunch (OPEFB) Fibres Reinforced Composites in Various Epoxy/Fibre Fractions

2021 ◽  
Vol 12 (5) ◽  
pp. 6148-6163
Keyword(s):  
Sodium Hydroxide ◽  
Oil Palm ◽  
Fiber Composite ◽  
Tensile Tests ◽  
Empty Fruit Bunch ◽  
Reinforced Composites ◽  
Soaking Time ◽  
Single Fibers ◽  
The Matrix ◽  
Treated Fiber

Oil palm empty fruit bunch (OPEFB) single fibers and reinforced composites were comprehensively characterized through tensile tests to assess their performance as potential reinforcing materials in polymer composites. The performances of OPEFB single fibers and reinforced composites with untreated and treated fibers conditions were compared. The fibers were variously treated with 3% sodium hydroxide, 2% silane, 3% sodium hydroxide mixed with 2% silane, and 3% sodium hydroxide prior to 2% silane for 2 hours soaking time. The highest toughness of the single fibers test was then selected to proceed with composites fabrication. The OPEFB composites were fabricated in 90:10, 80:20, 70:30, and 60:40 epoxy-fibre fractions. The result shows that the selected treated fiber composite exhibits better performance. The selected treated fiber composite increased the highest ultimate tensile strength by 145.3% for the 90:10 fraction. The highest Young’s Modulus was increased by about 166.7% for 70:30 fraction. Next, the highest toughness was increased by 389.5% for the 30:70 fraction. The treated fibers provided a better interlocking mechanism between the matrix and fibers in reinforced composites, thus improving their interfacial bonding.

Machining parametric study on the natural fiber reinforced composites: A review

2021 ◽  
pp. 095440622110637
Author(s):  
Vijay Kumar Mahakur ◽  
Sumit Bhowmik ◽  
Promod Kumar Patowari
Keyword(s):  
Natural Fiber ◽  
Low Cost ◽  
Natural Fibers ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Machining Processes ◽  
Industrial Sectors ◽  
The Matrix ◽  
Input Variables

Nowadays, the utilization of natural fiber reinforced composite has increased frequently. These natural fibers have significant features like low cost, renewable, and, more importantly, biodegradable in nature, making them to be utilized for various industrial sectors. However, the massive demand for natural fiber reinforced composites (NFRC), forces them to be machined and operated, which is required for countless areas in multiple industries like automotive, marine, aerospace and constructions. But before obtaining the final shape of any specimen, this specimen should come across numerous machining processes to get the desired shape and structure. Therefore, the present review paper focused on the various aspects during conventional and unconventional machining of the NFRC. It covers the work by exploring the influence of all input variables on the outcome produced after machining the NFRC. Various methodologies and tools are also discussed in this article for reducing the machining defects. The machining of the NFRC is found as a challenging task due to insufficient interlocking between the matrix and fibers, and minimum knowledge in machining characteristics and appropriate input parameters. Thus, this review is trying to assist the readers to grasp a basic understanding and information during the machining of the NFRC in every aspect.

Shear Load Transfer in Shape Memory Alloy Fiber Reinforced Composites During Elastic Axisymmetric Deformations

2000 ◽  
Author(s):  
Hungyu Tsai ◽  
Xinjian Fan
Keyword(s):  
Phase Transformation ◽  
Stress Concentration ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Transition Layer ◽  
Load Transfer ◽  
Fiber Reinforced Composites ◽  
Shear Load ◽  
Reinforced Composites ◽  
The Matrix

Abstract The axisymmetric elastic deformations in shape memory alloy (SMA) fiber reinforced composites are studied. We analyze the stress concentration near the interface between the fiber and the matrix as a result of a pre-described phase transformation in the active fiber. A typical model involving a single infinite fiber embedded in an infinite elastic matrix is studied. A portion of the fiber is allowed to undergo phase transformation along the axial direction so that its length is changed by the corresponding transformation strain (typically a few percentages), while the matrix is assumed to be linearly elastic and isotropic. Under certain bonding conditions, the deformation of fiber forces the matrix to deform in the elastic regime in order to accommodate the transformation strains. The problem is formulated as axisymmetric deformations coupled with a finite transformation region in the fiber. In order to avoid infinite stresses found under perfect bonding conditions, we adopt a “spring” model which accounts for the elasticity of a transition layer at the interface. This model allows for relative displacements between the fiber and the matrix. A linear relation between this relative displacement and the shear stress is used. The exact elasticity solution (in integral form) to this problem is found using Love’s stress function and Fourier transform. Numerical integration is performed to produce the stress distributions. In particular, the shear load transfer profiles along the interface are calculated for various spring stiffness. It is found that the singularity is eliminated and the stress concentration factor depends on the stiffness of the transition layer.

scholarly journals Efficient Hydrophobic Modification of Old Newspaper and Its Application in Paper Fiber Reinforced Composites

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 842 ◽  
Author(s):  
Weiwei Zhang ◽  
Jin Gu ◽  
Dengyun Tu ◽  
Litao Guan ◽  
Chuanshuang Hu
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Natural Fiber ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Oh Groups ◽  
Uniform Dispersion ◽  
The Matrix ◽  
Paper Fibers

Paper fibers have gained broad attention in natural fiber reinforced composites in recent years. The specific problem in preparing paper fiber reinforced composites is that paper fibers easily become flocculent after pulverization, which increases difficulties during melt-compounding with polymer matrix and results in non-uniform dispersion of paper fibers in the matrix. In this study, old newspaper (ONP) was treated with a low dosage of gaseous methyltrichlorosilane (MTCS) to solve the flocculation. The modified ONP fibers were characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis (TG). Then the modified ONP fibers and high-density polyethylene (HDPE) were extruded and pelletized to prepare ONP/HDPE composites via injection molding. Maleic anhydride-grafted polyethylene (MAPE) was added to enhance the interfacial bonding performance with the ultimate purpose of improving the mechanical strength of the composites. The mechanical properties such as tensile, flexural, and impact strength and the water absorption properties of the composite were tested. The results showed that the formation of hydrogen bonding between ONP fibers was effectively prevented after MTCS treatment due to the reduction of exposed –OH groups at the fiber surface. Excessive dosage of MTCS led to severe fiber degradation and dramatically reduced the aspect ratio of ONP fibers. Composites prepared with ONP fibers modified with 4% (v/w) MTCS showed the best mechanical properties due to reduced polarity between the fibers and the matrix, and the relatively long aspect ratio of treated ONP fibers. The composite with or without MAPE showed satisfactory water resistance properties. MTCS was proven to be a cheap and efficient way to pretreat old newspaper for preparing paper fiber reinforced composites.

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