Stress field analysis around optical fiber embedded in composite laminae under transverse loading

U ovome radu analiziran je uticaj ugrađenog optičkog vlakna na naponsko stanje transferzalno opterećene kompozitne lamine. Ugrađeno optičko vlakno ima primetan uticaj na naponsko polje kompozitne lamine. Vrednosti komponentnih napona u lamini sa ugrađenim optičkim vlaknom imaju i do 40% veće vrednosti od nominalnih. Za razmatrani slučaj opterećenja optičko vlakno ugrađeno u kompozitnu laminu jeste generator primetnih ali ne i značajnih koncentracija napona u poređenju sa onima koje, na primer, mogu da se jave usled geometrije oblika.The influence of embedded optical fiber on stress state of transversally loaded composite laminae was analyzed in this paper. The optical fiber interaction with the host material (composite) has noticeable effect on the stress field of laminae. For considered load case, values of the component stresses in laminae with embedded optical fiber have values up to 40% higher than the nominal ones. For the observed loading scenario, optical fibers are acting as generators of evident but not significant stress, comparing to the stress concentrations that could arise, for instance, as a consequence of the shape geometry

Model izvlačenja tankih staklenih traka iz predoblika

A one-dimensional model of thin glass sheet drawing has been developed. This model includes momentum, heat and mass balance equations. The density, viscosity and specific heat of the glass were calculated as functions of temperature, and the glass emissivity was defined and calculated as a function of both temperature and glass thickness. After allowed simplifications, two ordinary differential equations were obtained and solved using the Runge Kutte method. The model was used to investigate the influence of different process parameters (the velocity of lowering the preform into the furnace, the axial temperature profile of the furnace, the drawing force and its direction, etc.) on the change in the shape of the drawn glass sheet for different glass compositions and various geometrical characteristics of the preform. A laboratory device for drawing glass sheets from rectangular preforms enabled full control of the process parameters, their measurement, as well as data acquisition. The results of the numerical simulation were compared with the experimental data and good agreement between them was found

Modeling of coating optical fibers with polymer-magnetic powder composite coating

A mathematical model of forming a composite coating on optical fiber was established. The model is based on existing mathematical models for coating optical fibers with polymer coating and experimentally defined rheological behavior of the investigated dispersed system. The model was developed for a dispersed system consisting of poly(ethylene-co-vinyl acetate) - EVA in a form of toluene solution and powders of magnetic materials (BaFe12O19 and SmCo5). The influence of the die diameter, diameter of the original optical fiber, concentration of EVA and magnetic powders on the thickness of composite coating was investigated. The model shows good agreement with experimental data.Postavljen je matematički model formiranja kompozitne prevlake na optičkom vlaknu. Model je zasnovan na postojećim matematičkim modelima prevlačenja vlakana polimernom prevlakom i eksperimentalno utvrđenom reološkom ponašanju ispitivanog dispeznog sistema. Model je razvijen za disperzni sistem koji čine rastvor poli(etilen-ko-vinil acetat) EVA u toluenu i prahovi permanentnih magnetnih materijala (BaFe12O19 i SmCo5). Ispitivan je uticaj prečnika dizne, prečnika osnovnog vlakna, koncentarcije EVA i magnetnih prahova na debljinu kompozitne prevlake. Model pokazuje dobro slaganje sa eksperimentalnim podacima

The influence of heat treatment and finishing on the mechanical properties of laminar composites

The aim of this investigation was to define the optimum conditions of obtaining glass fabric - epoxy resin laminar composites with appropriate mechanical properties that satisfy the quality needed for production of printed circuit boards for microelectronics. Commercial materials: domestic glass woven fabric, different types of silane finish and epoxy resin were starting materials in obtaining composites. The conditions needed for the thermal removal of the original size from glass fabric were investigated. The optimal heat treatment should be performed on temperatures less than 550C, while cooling rate should be as slow as possible. In this manner the fabric has less than 0.1% of residual size, and the mechanical properties remain satisfactory. Two most commonly used silane based finishes were applied on heat-treated glass fabric. Tensile strength of the composite material made of thermally and chemically treated glass fabric and epoxy resin was investigated. The possibility of using domestic glass fabric in production of printed circuit boards for microelectronics has been confirmed. Finish with amino functional group and lower heat treatment temperature should be used for obtaining glass-fabric epoxy resin laminar composites with desirable mechanical properties

Electrical Conductivity of Lignocellulose Composites Loaded with Electrodeposited Copper Powders. Part II. Influence of Particle Size on Percolation Threshold

This article is concerned with synthesis and characterization of electroconductive composite materials prepared by the compression molding of mixtures of lignocellulose and electrochemically deposited copper powder under different pressures, and investigation of the influence of particle size on conductivity and percolation threshold of obtained composites. Electrodeposited copper powder content was varied from 2.0-29.8 vol%. Analysis of the most significant properties of individual components and prepared composites included structural and morphological analysis and measurements of hardness and electrical conductivity. Hardness of the investigated composites, as expected, increased with the increase of the processing pressure, as well as lowering the particle size compared to previous work. The significant increase of the electrical conductivity can be observed as the copper powder content reaches the percolation threshold. The packaging effect and more pronounced interpartical contact with smaller, highly porous, highly dendritic particles with high values of specific area lead to "movement" of percolation threshold towards lower filler content, which for the particles LT 45 mu m and highest processing pressure of 27 MPa was 7.2% (v/v). In the investigated range of electrodeposited copper powder concentrations and applied pressures the increase of the electrical conductivity of composites is as much as fourteen orders of magnitude. It was found that this transition occurs at lower volume fractions than stated in the literature which can be due to the filler with high specific area

Influence of Electrolytic Copper Powder Particle Morphology on Electrical Conductivity of Lignocellulose Composites and Formation of Conductive Pathways

Composites based on polymers with conductive fillers have been gaining more significant roles in a variety of technological domains and they are getting in the research focus of numerous studies as a part of growing research trend. Galvanostatically produced copper powder with high values of specific area was used as filler for synthesis of electroconductive composite materials prepared by the compression molding of mixtures of lignocellulose and electrochemically deposited copper powder. This article is concerned with characterization of these composites. Analysis of the most significant properties of prepared composites and its components included measurements of electrical conductivity, impedance spectroscopy (IS) behavior and structural and morphological analysis. Volume fraction of the copper powder was varied from 2.0-29.8% (v/v). The significant increase of the electrical conductivity can be observed as the copper powder content reaches the percolation threshold (PT). It was shown that PT depends on both particle shape and type of spatial distribution. IS measurements have shown that particle morphology having pronounced grain boundaries has great effect on appearance of electric conductive layers. The packaging effect and more pronounced interpartical contact with copper powder particles lead to "movement" of PT, which for the particles LT 45 mu m and highest processing pressure of 27 MPa was 7.2% (v/v). IS response of the composites showed existence of electrical conductive layers, each having different resistivity which increases towards interior of the composite

Mechanical and magnetic properties of composite materials with polymer matrix

Many of modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. Material property combinations and ranges have been extended by the development of composite materials. Development of Nd-Fe-B/polymer composite magnetic materials has significantly increased interest in research and development of bonded magnets, since particles of Nd-Fe-B alloys are proved to be very suitable for their production. This study investigates the mechanical and magnetic properties of compression molded Nd-Fe-B magnets with different content of magnetic powder in epoxy matrix. Mechanical properties were investigated at ambient temperature according to ASTM standard D 3039-00. The obtained results show that tensile strength and elongation decrease with an increase of Nd-Fe-B particles content in epoxy matrix. The modulus of elasticity increases, which means that in exploitation material with higher magnetic powder content, subjected to the same level of stress, undergoes 2 to 3.5 times smaller deformation. Scanning Electron Microscopy (SEM) was used to examine the morphology of sample surfaces and fracture surfaces caused by the tensile strength tests. The results of SQUID magnetic measurements show an increase of magnetic properties of the investigated composites with increasing content of Nd-Fe-B particles

Microhardness analysis of thin metallic multilayer composite films on copper substrates

Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness

Mikromehanička svojstva kompozitnih sistema formiranih elektrohemijskim taloženjem filmova nikla i bakra na različitim podlogama

Fine-grained nickel and copper thin films were electrodeposited (ED) from self-made sulphamate and sulphate electrolytes, respectively, on different substrates. The substrates were single crystal silicon with two different orientations, namely (100) and (111) and bulk electrodeposited Ni films. Nickel films on Si substrate and ED Cu films on bulk ED Ni substrate can be thought as composite systems of 'soft film on hard substrate' type. The influence of the substrate layer and chosen plating conditions on mechanical properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participates in the plastic deformations during the indentation process. Composite hardness models of Jonsson-Hogmark (J-H), Burnett-Rickerby (B-R) and Korsunsky (K) do not fit experimental data for this type of composite system well. Chicot-Lesage (C-L) model based on the model for reinforced composites can be applied to experimental data even for the thick coatings (50 mm). Model (C-L) for reinforced composites was chosen for all specimen and the film hardness was calculated, for each indentation diagonal. The values obtained for the film hardness HF are influenced by the applied load. In case of the system of ED Ni film on Si substrate, film hardness lines have descending character, but in case of the ED Cu film on bulk ED Ni substrate, the film hardness increases. The variations should be related to physical phenomena such as the indentation size effect, the cracking in the neighborhood of the indent, the elastic contribution of the substrate for the lowest loads, or the crushing of the film for the highest loads.Elektrohemijskim taloženjem (ET) tankih filmova Ni i Cu na različitim podlogama, monokristalnom silicijumu orijentacija (100) i (111) i masivnom elektrohemijski istaloženom filmu Ni, formirani su kompozitni sistemi tipa 'mekog filma na tvrdoj podlozi'. Sitnozrni talozi Ni i Cu su bili dobijeni iz dva različita elektrolita pod odabranim uslovima elektrolize, Ni iz sulfamatnog i Cu iz sulfatnog elektrolita.U cilju određivanja mehaničkih svojstava ovih kompozitnih sistema, i posebno, određivanja svojstava filmova u okviru sistema, izvršena su merenja mikrotvrdoće utiskivanjem po Vikersovoj metodi za različita opterećenja. Izmerena vrednost mikrotvrdoće opisuje kompozitni sistem u celini i naziva se 'kompozitnom mikrotvrdoćom'. Ona ne predstavlja apsolutnu tvrdoću elektrohemijski istaloženog filma zbog učešća podloge u plastičnoj deformaciji tokom utiskivanja. Model Šiko-Lezaža (Chicot-Lesage) se pokazao odgovarajućim za analizu apsolutne tvrdoće tankih filmova za kompozitne sisteme 'mek film na tvrdoj podlozi' i primenjen je na eksperimentalne rezultate