Kinds Of Composites Research Articles

A review on machining of carbon fiber reinforced ceramic matrix composites

Abstract Carbon fiber reinforced ceramic matrix ceramic/polymers composites have excellent physical-mechanical properties for their specific strength, high hardness, and strong fracture toughness relative to their matrix, and they also possess a good performance of wear resistance, heat resistance, dimensional stability, and ablation resistance. It is a choice for thermal protection and high temperature structural materials. However, this kind of composites owning characteristics of high hardness and abrasion is difficult to machine which impedes the large-scale industrial application of manufacturing. This paper mainly reviews the research on machining status of carbon fiber reinforced ceramic matrix composites including carbon fiber reinforced polymer matrix composites from the aspects of conventional machining and unconventional machining method. The machining trends, problems existing in various machining methods and corresponding solutions are generalized and analyzed.

Epoxy Composites Based on Low-cost Carbon Filler Derived from Hydrothermal Carbonization of Waste

Different kinds of composites based on polymer matrix are present on the market. In particular, composites based on epoxy resin are used as high-performance polymers due to their excellent mechanical properties, chemical resistance, thermal stability and low cost production. Recently, in composites production the attention has been focused on the study of materials derived from biomass and organic waste to be used as filler.Hydrochar is a carbonaceous material obtained from hydrothermal carbonization (HTC) of biomasses and organic waste. During HTC biomass is carbonized in an aqueous environment at temperatures of 180-250?°C under saturated pressure (autogenous or provided by a gas) for several hours. For its characteristics, hydrochar can be potentially used as filler in composite materials in view of the growing concern about environmental sustainability.In this work, hydrochar obtained from hydrothermal carbonization of green waste was used as filler for the preparation of diglycidyl ether of bisphenol A-type epoxy composite materials. Two different epoxy matrices were used; the content of hydrochar was varied between 5 and 15 wt%. The resulting samples were characterized by morphologic and mechanical analyses, and electrical properties were evaluated. The addition of hydrochar to epoxy resins resulted in a slight increase of the elastic modulus, although there was a decrease in tensile strength and toughness. Moreover, electrical properties of epoxy resins were not significantly modified by the addition of hydrochar. Therefore, the study provided encouraging results for the production of innovative hydrochar-based epoxy composites, allowing the recycling and re-use of industrial waste.

Scale Effect on Impact Performance of Unidirectional Glass Fiber Reinforced Epoxy Composite Laminates.

As a result of the increasing use of glass fiber reinforced plastic (GFRP) composites in engineering fields, the investigation of scale effect on impact performance for this kind of composite is essential for large scale structure design. The effects of scaling on the impact response of simply supported unidirectional GFRP were investigated through drop weight impact (DWI) tests in this study. Impact tests were undertaken over a wide range of energies to generate damages between barely visible and initiated penetration on four scale size GFRP laminates. The main impact responses including impact force, contact duration, displacement, energy absorption and damage area of scaled specimens were normalized to compare with the full-size specimen. It was found that the impact response of large sample with elastic deformation and small area of delamination can be predicted accurately according to a geometrical similar scaling law. Scale effect was found in the damage threshold force and absorbed energy of the laminates when significant internal damage occurs due to the microstructural effect becoming important in resisting impact force and absorbing impact energy. Moreover, the energy partition and effective stiffness were calculated according to the energy balance model to reveal the contribution of different modes of deformations on energy absorption for the GFRP laminates.

Plotinus on Divine Simplicity

AbstractGavrilyuk attends to divine simplicity according to the third‐century AD pagan philosopher Plotinus. He shows that Plotinus draws his doctrine of divine simplicity from the earlier Greco‐Roman philosophical tradition, in which the nature of the “first principle” was highly contested. Aristotle offers a history of the early debate, with Anaxagoras being the first to glimpse the first principle’s simplicity. The Platonist philosophers conceived of the first principle as incorporeal, and on these grounds linked the first principle to simplicity. For his part, Aristotle associated simplicity with the absoluteness of pure actuality. The Stoics, with their essentially material understanding of the divine, ignored or denied divine simplicity. Plotinus draws upon the reception of Aristotle that is found in Alexander of Aphrodisias, Numenius, and Ammonius. According to Gavrilyuk, the signal contribution of Plotinus consists in setting forth the strongest possible doctrine of divine simplicity. Indeed, for Plotinus God’s utter simplicity means that God cannot even be thought, because thinking requires the duality of subject‐object. Plotinus conceives of the divine One as above divine Mind (nous), since the latter contains a unified plurality but not the perfect simplicity that marks the unknowable One. Gavilyuk ends his essay with an account of the qualifications made to divine simplicity by philosophers and theologians who are less radical in their doctrine than is Plotinus. He emphasizes that the Enneads’s key metaphysical insight, utterly ruling out any kind of composition from the One, has the benefit of being supremely intellectually coherent and elegant.

Preparation of fibrin gel scaffolds containing MWCNT/PU nanofibers for neural tissue engineering.

Compared to the peripheral nervous system, in the central nervous system (CNS) disorders, neurons are less able to regenerate and reconstruct the neural tissue. Tissue engineering is considered as a promising approach for neural regeneration and restoring neurologic function after CNS injuries. Nanofibrous hydrogels have been recently used as three-dimensional (3D) scaffolds for tissue engineering applications. In this kind of composites, hydrogels are incorporated with fibers to enhance their poor mechanical properties. Furthermore, introducing meshes within hydrogels can result in composites associated with advantages of both components. In the present study, we have prepared 3D nanofibrous hydrogel scaffolds based on fibrin/polyurethane/multiwall carbon nanotube (fibrin/PU/MWCNT), for application as composite scaffolds for neural tissue engineering. The fabricated fibrin/PU/MWCNT hydrogel scaffolds were characterized and their ability to support cell attachment and viability was assessed in comparison with fibrin hydrogel. Scanning electron microscopy (SEM) analysis was performed to examine the microstructural features of scaffolds. The rate of biodegradation and rheological properties of scaffolds were also investigated. After isolation of human endometrial stem cells (hEnSCs), they were cultured into the scaffolds, then their attachment and viability were assessed through SEM analysis, MTT assay and DAPI staining. Based on the results, the viability and proliferation of hEnSCs in the fibrin/PU/MWCNT hydrogels were higher than those in fibrin hydrogels. Therefore, our novel fabricated fibrin/PU/MWCNT hydrogel is able to support cell proliferation and can be used as a scaffold to provide an appropriate microenvironment for enhancing cell viability. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 802-814, 2019.

Pea-like Fe/Fe3C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes with Tunable Dielectric/Magnetic Loss and Efficient Electromagnetic Absorption.

One-dimensional microstructure has been regarded as one of the most desirable configurations for magnetic carbon-based microwave absorbing materials (MAMs). Herein, pea-like Fe/Fe3C nanoparticles embedded in nitrogen-doped carbon nanotubes (Fe/Fe3C@NCNTs) are successfully prepared through a direct pyrolysis of the mixture of FeCl3·6H2O and melamine under inert atmosphere. The chemical composition and microstructural feature of these Fe/Fe3C@NCNTs composites are highly dependent on the pyrolysis temperature. As a result, their electromagnetic properties can be also manipulated, where dielectric loss gradually decreases with the increasing pyrolysis temperature and magnetic loss presents a reverse variation trend. When the pyrolysis temperature reaches 600 °C, the as-obtained composite, Fe/Fe3C@NCNTs-600 can perform a maximum reflection loss of -46.0 dB at 3.6 GHz with a thickness of 4.97 mm and a qualified bandwidth of 14.8 GHz with the integrated thickness from 1.00 to 5.00 mm. It is very interesting that the microwave absorption performance of this new kind of composites is not so susceptible to the pyrolysis temperature as those common magnetic carbon-based MAMs because there is an effective balance between dielectric loss and magnetic loss, which accounts for a very stable attenuation ability when the pyrolysis temperature range changes from 600 to 700 °C. These favorable characteristics, including low-cost raw materials, easy preparation, and stable performance, may render Fe/Fe3C@NCNTs composites as a novel kind of MAMs in the future.

Fragmentation model for the tensile response of unidirectional composites based on the critical number of fiber breaks and the correction of the fiber-matrix interfacial strength.

Abstract A fragmentation model based on global load sharing (GLS) theory is developed to obtain stress-strain curves that describe the mechanical behavior of unidirectional composites. The model is named CNB+τ* because it is based on the Critical Number of Breaks model (CNB) and on the correction of the fiber matrix interfacial strength, τ*. Model allows both obtaining the ultimate tensile strength of CFRP and GFRP composites, and correcting the σ vs e curve to match its peak point with the predicted strength, which is more accurate than the one obtained by previous GLS-based models. Our model is used to classify the mechanical response of the material according to the energetic contributions of two phenomena up to the failure: intact fibers (IF) and fragmentation (FM). Additionally, the influence of fiber content, Vf, on the tensile strength, σU, failure strain, eU, and total strain energy, UT, is analyzed by means of novel mechanical-performance maps obtained by the model. The maps show a dissimilar behavior of σU, eU and UT with Vf between GFRP and CFRP composites. The low influence of Vf on the percent energetic contributions of IF and FM zones, as well as the larger energetic contribution of the FM zone, are common conclusions that can be addressed for both kinds of composites.

Numerical research on elasto-plastic behaviors of fiber-reinforced polymer based composite laminates

A new pressure-dependent elasto-plastic constitutive model for polymer based composite laminates with unidirectional plies is established and implemented into finite element software to simulate off-axis loading tests of two kinds of composites. The validity of the new plasticity model is proved by available off-axis loading test results. Additionally, accuracies and efficiencies of the backward Euler algorithm and the forward Euler algorithm respective in solving plastic deformation of fiber-reinforced composite materials are analyzed. Compared with the forward Euler algorithm based plasticity model, the backward Euler scheme shows comparative prediction accuracy of laminate plastic behavior and better computational efficiency. This paper is expected to facilitate the numerical predictions of composite laminates’ elasto-plastic behaviors for researchers and engineers.

Synthesis and Tribological Properties of Bio-Inspired Nacre-Like Composites

Ceramic materials possessing the properties of high-strength and rigidity are widely used in industry. The shell nacre has a layered structure containing both macroscopic and microscopic levels and is equipped with superior qualities regarding hardness and strength. Therefore, the ceramic composites with a nacre-like layered structure have the potential to be utilized as sliding bearings employed in the harsh conditions of wells. For the purpose of this paper, a porous Al2O3 ceramics skeleton with nanometer powder is prepared using the freeze-casting method. Then the porous ceramic skeleton is filled with polymer polymethyl methacrylate (PMMA) through mass polymerization to produce a bionic Al2O3/PMMA composite with a lamellar structure. The properties of the prepared composite are determined by the analysis of micro-hardness, fracture toughness, friction coefficient, wear scar diameter, and the morphology of the worn surface. Consequent results indicate that elevation in the A12O3 powder, which acts as the initial solid phase content, prompts the ceramic slurry to exhibit an increase in viscosity and a gradual decrease in the pore size of the ceramic skeleton. The prepared layered Al2O3/PMMA composite possesses high fracture toughness, which closely resembles that of Al, is approximately four times that of the matrix of the Al2O3 ceramics and 16 times that of the PMMA. Three kinds of composites containing different solid phase content are subjected to testing involving lubrication by water-based drilling fluid to determine the friction coefficient of each. The results indicate that an increased load leads to a decreased friction coefficient while the impact of speed is not evident. Under dry conditions, the friction coefficient of three different composites tested, declines with elevated load and speed. With the use of water-based drilling fluid as lubrication, the wear scar diameter increases at higher speed, while dry conditions denote increased load. Abrasive wear is determined to be the principal form of erosion of layered Al2O3/PMMA composites.

Comparison of different surface treatments of carbon fibers used as reinforcements in epoxy composites: Interfacial strength measurements by in-situ scanning electron microscope tensile tests

In-situ characterization of the fiber/matrix interfacial failure behavior at microscopic scale is important to optimize the fiber surface treatment and to design high performance composites. In this study, in-situ tensile tests in scanning electron microscope (SEM) were used to investigate the interfacial adhesion strength of epoxy composites reinforced by four kinds of carbon fibers (CF)—raw CF, desized CF, carbon nanotube-grafted CF (CNT-CF) and oxidized CNT-CF. The crack initiation position and fracture failure mode were well recorded. The strains and the interfacial adhesion strength were obtained for these four kinds of composites. It was found that the interfacial strength decreased from 53 MPa to 48 MPa after removing the sizing on carbon fiber surface. However, by grafting CNTs on the CF surface, the interfacial strength reached 55 MPa and was further increased to 58 MPa after a simple thermal oxidation treatment. Moreover, energy dispersion X-ray analysis (EDX) was carried out using scanning transmission electron microscopy (STEM). The EDX mapping demonstrated that oxygen aggregated at the interfaces of raw CF/epoxy and oxidized CNT-CF/epoxy. Thus, a combination of CNT grafting with chemical functionalization should be necessary to achieve high performance carbon fiber reinforced polymer composites.

Evaluation of Tensile and Thermal Behavior Analysis of Nano Carbon Fiber Reinforced Polymer Composite

Today a lot of research work is performed throughout the world on the use of natural fibers as a strengthening material introduced in the preparation of various kinds of composites, and also the use of natural fiber/polymer composites in civil and mechanical engineering fields are playing very important role due to its usage of natural resource and its properties. From the current journal, we have recently found NFRPC fibers which are extracted from NFRPC plants by involving hard physical work. In this journal, the tensile components of the six to seven months NFRPCare analyzed through various tests such as FTIR, XRD, SEM, THERMO GRAVIMETRIC ANALYSE and match with other available conventional all-natural fibers, and also examine the chemical qualities of NFRPC. The fiber of NFRPC has a high wax content, so it's easy to bind with materials like resin. SEM analyze also signifies the presence of voids on the interior surface of the fiber material. and the results show that the NFRPC provides good Tensile and Thermal properties.

Preparation and Mechanical Properties of Polypropylene Composite for Seats

This paper describes the effects of the Multiwalled Carbon Nanotubes (MCNs)of different masses on the mechanical properties of polypropylene/calcium sulfate whisker composites for seats. With a twin roller open mill, a kind of composite PP-g-MAH/CSW/NWNTS may be made from surface-modified MCNs and modified calcium sulfate whiskers, polypropylene (PP), maleic anhydride grafted polypropylene (PP-g-MAH) using melt blending method, thereby to compare which effects the modified MCN of different doses plays on the mechanical properties of the PP/PP-g-MAH/CSW/NWNTS composites for sports seats. This study shows that the MCNs that have a mix-acid treatment on the surface uniformly disperse in the composite material, and well bond with the interface of the polymer matrix, thus playing a function for toughening and strengthening composite material. But worse, when the mass fraction of carbon nanotubes is higher, there is a phenomenon of agglomeration occurred, which in turn worsens the mechanical properties of the composite material. The carbon nanotubes at approx. 0.5%make the mechanical properties of the composite the best.

Compounds Identification in Semen Cuscutae by Ultra-High-Performance Liquid Chromatography (UPLCs) Coupled to Electrospray Ionization Mass Spectrometry.

Semen Cuscutae is commonly used in traditional Chinese medicine and contains a series of compounds such as flavonoids, chlorogenic acids and lignans. In this study, we identified different kinds of compositions by ultra-high-performance liquid chromatography (UPLC) coupled to electrospray ionization mass spectrometry (MS). A total of 45 compounds were observed, including 20 chlorogenic acids, 23 flavonoids and 2 lignans. 23 of them are reported for the first time including 6-O-caffeoyl-β-glucose, 3-O-(4′-O-Caffeoylglucosyl) quinic acid, etc. Their structures were established by retention behavior, extensive analyses of their MS spectra and further determined by comparison of their MS data with those reported in the literature. As chlorogenic acids and flavonoids are phenolic compounds that are predominant in Semen Cuscutae, in conclusion, phenolic compounds are the major constituents of Semen Cuscutae.

All-cellulose composites based on the self-reinforced effect

Abstract All-cellulose composites (ACCs) are mono-component cellulose-based composites, in which the matrix is regenerated cellulose and the reinforcing phase is generally composed of high-strength cellulose fibers. This kind of composite is featured by its good interfacial compatibility, biocompatibility and biodegradability because of the same cellulosic composition of the matrix and reinforcing phase. The as-prepared ACCs display superior mechanical, optical and barrier properties and are becoming the most promising all-biomass materials. In this short review, we summarize the preparation methods and controllable parameters of ACCs, point out the main influencing factors and effective strategies to improve their properties, and present the challenges and prospects in this field.

Fabrication and characterization of ZrO2/Ni composites

This paper focuses on a research on the influence of nickel content in zirconia matrix and its impact on the mechanical properties of obtained composites. ZrO2/Ni mixed powders were uniaxially pressed and sintered in a nitrogen atmosphere to obtain ZrO2/Ni composites that were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). The stereological analysis allows obtaining information about the size distribution of zirconia grains in the sintered composites. Relative density, hardness, fracture toughness, and bending strength were also analyzed. The results revealed that the presence of Ni particles in the composites affects the mechanical properties of the materials. An increased Ni concentration caused a decrease in Vickers hardness and increased the fracture toughness of the ZrO2/Ni composites compared to the ZrO2 samples. This kind of composite is of interest for temperature and flow sensors, thermal barrier coatings for gas turbines and supersonic propulsion systems of spacecrafts, as well as as a material for anode in solid oxide fuel cell.

Green poly(β-hydroxybutyrate)/starch nanocrystal composites: Tuning the nucleation and spherulite morphology through surface acetylation of starch nanocrystal

Starch nanocrystal (SNC) particles were used as the filler to prepare green composites with biodegradable poly(β-hydroxybutyrate) (PHB). An interesting way to tune the nucleation and banded morphology of composites by the surface acetylation of SNC was proposed. Pristine SNC acts as the nucleating agent, while acetylated SNC as the antinucleation one to PHB. This role switching is due to improved polymer-particle compatibility after surface acetylation of SNC particles. The banded structure of PHB spherulites degrades evidently in the presence of two kinds of SNC particles, showing decreased ring-band space, with deteriorated periodicity and increased flocculation of peak-to-valley height. But the two kinds of composites have different mechanisms on the degradation of their ring-bands because the two kinds of SNC particles, pristine SNC and acetylated one, have different influences on the PHB spherulite growth rates and system undercooling. This work also opens a new window for the applications of SNC particles.

Comparative investigation on microstructures and mechanical properties of (TiB + TiC)/Ti-6Al-4V composites from Ti-B4C-C and Ti-TiB2-TiC systems

Two percentages of TiB + TiC reinforced Ti-6Al-4V composites from Ti-B4C-C and Ti-TiB2-TiC systems were fabricated by reactive hot-pressed sintering. Their microstructures and mechanical properties involving elastic modulus, Vickers hardness, bending strength and wear property were investigated comparatively. The experimental results show that needle-like TiB whiskers and near-equiaxed TiC particles are evenly distributed in the Ti-6Al-4V matrix. The mechanical properties of the (TiB + TiC)/Ti-6Al-4V composites are closely related with the nominal composition and synthesis system of TiB + TiC reinforcement and the microstructures of composites. With increasing the nominal volume fraction of reinforcement, both elastic modulus and Vickers hardness increase more or less and the bending strength decreases in varying degrees. A certain increase of pores in the composites with the sintering temperature increasing to 1300 °C can markedly affect the bending strength. Moreover, no matter what the sintering temperature and nominal volume fraction of reinforcement, the elastic modulus and Vickers hardness of composites from the Ti-TiB2-TiC system are higher than those from the Ti-B4C-C system. Similarly, the composites from the Ti-B4C-C system present better abrasion resistance than those from the Ti-TiB2-TiC system due to the difference of interfacial bonding between the TiC particles and Ti-6Al-4V matrix in the two kinds of composites.

THE ERROR ANALYSIS OF DERIVATIONAL MORPHOLOGY IN EFL ENGLISH NARRATIVE COMPOSITIONS

Derivational morphology in the learners’ English narrative compositions was the main purpose of this research. Morphology is the study of morphemes which are the smallest significant units of grammar. There are two kinds of morphology: derivational and inflectional morphology. Derivational morphology is related to affixes such as suffixes, infixes, prefixes, ablaut and reduplication, meanwhile inflectional morphology is related to plural, possessive, past time, progressive, and comparative and superlative. Morphology mostly used in writing and it is one of the difficult parts in English subject. There are four kinds of composition: argumentation, description, exposition and narration. The data was taken from the students of grade XI of a Public High School in Tangerang. Descriptive method was used in this paper. There is some derivational morphology found in this research: derivation of a noun, adverb, gerund after a preposition, gerund after the verb, to-infinitive, present participle, passive participle, modals, and adjective.

SERS and the photo-catalytic performance of Ag/TiO2/graphene composites

Three kinds of reusable surface enhanced Raman scattering (SERS) substrates based on Ag-TiO2-G, Ag-G-TiO2 and G-Ag-TiO2 hybrid structures were prepared by a combination method of simple sol-gel self-assembly and annealing. The composites were confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Raman mapping spectra of the three hybrids were analyzed in order to study the difference of charge transfer between Ag, TiO2 and graphene. In addition, rhodamine 6G (R6G) was used as the probe analyte, and the SERS activity of the three structures decreased orderly in the sequence of Ag-G-TiO2, G-Ag-TiO2, and Ag-TiO2-G, with the enhancement factor of about 106, which was due to the high electromagnetic enhancement of the Ag nanoparticles (AgNPs). The photo-catalytic properties of the three kinds of composites were experimentally studied via Raman mapping measurements through UV irradiation. The photocatalytic ability decreased also orderly in the sequence of Ag-G-TiO2, G-Ag-TiO2, and Ag-TiO2-G, and the reason was discussed in details.

Evaluation of Mechanical Properties of Natural Fiber Reinforced Melamine Urea Formaldehyde (MUF) Resin Composites

Natural fibers have lot of merits over other established materials as reinforcement which recently attracted the attention of researchers. They are environmentally-friendly, fully biodegradable, abundantly available, easily accessible, non-toxic, non-abrasive, renewable, cheap, and have low density. In this project, five kinds of composites were developed by using different combinations of resins and fibers by hand lay- up process. The Melamine Urea Formaldehyde resin (MUF) and polyester resin are used as the binding agents. Khadi, coconut leaf midrib (CLM) and glass fibers are used as reinforcing materials for developing the composites. Later, mechanical properties like elastic modulus and impact strength of the developed composites are evaluated by using static bending and impact tests. The results show that the Young’s modulus and specific modulus of composites prepared from MUF resin is greater than that of composites prepared from polyester resin. Among the five composites Khadi-CLM hybrid with MUF shows highest specific modulus. MUF shows fairly good properties with natural fibers as well as with artificial fibers. On the other hand polyester resin shows its apex result only with artificial fiber (Glass), this may be due to the good binding property of MUF resin with natural fibers.