Search results for: engineered cementitious composites

Authors: S. U. Durgadsimi, S. Chouguleb, S. Belladc

Abstract:

(y) Li0.5Ni0.7Zn0.05Fe2O4 + (1-y) Ba0.5Sr0.5TiO3 magnetoelectric composites with y = 0.1, 0.3 and 0.5 were prepared by a conventional standard double sintering ceramic technique. X-ray diffraction analysis confirmed the phase formation of ferrite, ferroelectric and their composites. logρdc Vs 1/T graphs reveal that the dc resistivity decreases with increasing temperature exhibiting semiconductor behavior. The plots of logσac Vs logω2 are almost linear indicating that the conductivity increases with increase in frequency i.e, conductivity in the composites is due to small polaron hopping. Dielectric constant (έ) and dielectric loss (tan δ) were studied as a function of frequency in the range 100Hz–1MHz which reveals the normal dielectric behavior except the composite with y=0.1 and as a function of temperature at four fixed frequencies (i.e. 100Hz, 1KHz, 10KHz, 100KHz). ME voltage coefficient decreases with increase in ferrite content and was observed to be maximum of about 7.495 mV/cmOe for (0.1) Li0.5Ni0.7Zn0.05Fe2O4 + (0.9) Ba0.5Sr0.5TiO3 composite.

Keywords: XRD, dielectric constant, dielectric loss, DC and AC conductivity, ME voltage coefficient

Procedia PDF Downloads 317

Authors: Dhaladhuli Pranavi, Amirtham Rajagopal

Abstract:

There are various failure modes in ceramic matrix composites; notable ones are fiber breakage, matrix cracking and fiber matrix debonding. Crack nucleation and propagation in microstructure of such composites requires an understanding of interaction of crack with the multiple inclusion heterogeneous system and interfaces. In order to assess structural integrity, the material parameters especially of the interface that governs the crack growth should be determined. In the present work, a nonlocal phase field approach is proposed to model the crack interface interaction in such composites. Nonlocal approaches help in understanding the complex mechanisms of delamination growth and mitigation and operates at a material length scale. The performance of the proposed formulation is illustrated through representative numerical examples. The model proposed is implemented in the framework of the finite element method. Several parametric studies on interface crack interaction are conducted. The proposed model is easy and simple to implement and works very well in modeling fracture in composite systems.

Keywords: composite, interface, nonlocal, phase field

Procedia PDF Downloads 113

Authors: Mohammed Abed, Rita Nemes

Abstract:

Cellular concrete powder (CCP) is not used widely as supplementary cementitious material, but in the literature, its efficiency is proved when it used as a replacement of cement in concrete mixtures. In this study, different amounts of raw CCP (CCP as a waste material without any industrial modification) will be used to investigate the characteristics of cement pastes and the effects of CCP on the properties of the cement pastes. It is an attempt to produce green binder paste, which is useful for sustainable construction applications. The fresh and hardened properties of a number of CCP blended cement paste will be tested in different life periods, and the optimized CCP volume will be reported with more significant investigations on durability properties. Different replacing of mass percentage (low and high) of the cement mass will be conducted (0%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%). The consistency, flexural strength, and compressive strength will be the base indicator for the further properties' investigations. The CCP replacement until 50% have been tested until 7 days, and the initial results showed a linear relationship between strength and the percentage of the replacement; that is an optimistic indicator for further replacement percentages of waste CCP.

Keywords: cellular concrete powder, supplementary cementitious material, sustainable construction, green concrete

Procedia PDF Downloads 295

Authors: H. M. Nanjundaswamy, S. K. Nath, S. Ray

Abstract:

TiO₂ particles have been added in molten aluminium to result in aluminium based cast Al/Al₃Ti-Al₂O₃ composite, which has been added then to molten magnesium to synthesize magnesium based cast Mg-Al/Al₃Ti-Al₂O₃ composite. The nominal compositions in terms of Mg, Al, and TiO₂ contents in the magnesium based composites are Mg-9Al-0.6TiO₂, Mg-9Al-0.8TiO₂, Mg-9Al-1.0TiO₂ and Mg-9Al-1.2TiO₂ designated respectively as MA6T, MA8T, MA10T and MA12T. The microstructure of the cast magnesium based composite shows grayish rods of intermetallics Al₃Ti, inherited from aluminium based composite but these rods, on hot forging, breaks into smaller lengths decreasing the average aspect ratio (length to diameter) from 7.5 to 3.0. There are also cavities in between the broken segments of rods. β-phase in cast microstructure, Mg₁₇Al₁₂, dissolves during heating prior to forging and re-precipitates as relatively finer particles on cooling. The amount of β-phase also decreases on forging as segregation is removed. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing addition of TiO₂ but the hardness is higher in forged composites by about 80 BHN. With addition of higher level of TiO₂ in magnesium based cast composite, yield strength decreases progressively but there is marginal increase in yield strength over that of the cast Mg-9 wt. pct. Al, designated as MA alloy. But the ultimate tensile strength (UTS) in the cast composites decreases with the increasing particle content indicating possibly an early initiation of crack in the brittle inter-dendritic region and their easy propagation through the interfaces of the particles. In forged composites, there is a significant improvement in both yield strength and UTS with increasing TiO₂ addition and also, over those observed in their cast counterpart, but at higher addition it decreases. It may also be noted that as in forged MA alloy, incomplete recovery of forging strain increases the strength of the matrix in the composites and the ductility decreases both in the forged alloy and the composites. Initiation fracture toughness, J_IC, decreases drastically in cast composites compared to that in MA alloy due to the presence of intermetallic Al₃Ti and Al₂O₃ particles in the composite. There is drastic reduction of J_IC on forging both in the alloy and the composites, possibly due to incomplete recovery of forging strain in both as well as breaking of Al₃Ti rods and the voids between the broken segments of Al₃Ti rods in composites. The ratio of tearing modulus to elastic modulus in cast composites show higher ratio, which increases with the increasing TiO₂ addition. The ratio decreases comparatively more on forging of cast MA alloy than those in forged composites.

Keywords: composite, fracture toughness, forging, tensile properties

Procedia PDF Downloads 221

Authors: Young-Cheol Choi, Sung-Won Yoo, Bong Chun Lee, Byoungsun Park, Sang-Hwa Jung

Abstract:

Cracks in concrete commonly provide the passages of ingresses of aggressive and harmful ions into concrete inside and thus reduce the durability of concrete members. In order to solve this problem, self-healing concrete based on mineral admixture has become a major issue. Self-healing materials are those which have the ability of autonomously repairing some damages or small cracks in concrete structures. Concrete has an inherent healing potential, called natural healing, which can take place in ordinary concrete elements but its power is limited and is not predictable. The main mechanism of self-healing in cracked concrete is the continued hydration of unreacted binder and the crystallization of calcium carbonate. Some mineral admixtures have been found to promote the self-healing of cementitious materials. The aim of this study is to investigate the effect of mineral admixture on the self-healing performances of high strength concrete. The potential capability of self-healing of cementitious materials was evaluated using isothermal conduction calorimeter. The self-healing efficiencies were studied by means of water flow tests on cracked concrete specimens. The results show a different healing behaviour depending on presence of the crystalline admixture.

Keywords: mineral admixture, self-healing, water flow test, crystallization

Procedia PDF Downloads 336

Authors: Haydar S. Al Shabbani, M. Marshall, R. Goodall

Abstract:

Metal matrix composites (MMCs) have been explored for many applications for many decades. Recently, this includes investigations for thermal applications associated with electronics, such as in heat sinks. Here, to promote thermal conductivity, composites of a metal matrix with diamond particles are used. However, this class of composites has not yet been extensively examined for mechanical and tribological behavior, especially for applications that require extreme mechanical and tribological strength, such as the resistance to abrasive cutting. Therefore, this research seeks to develop a composite material with metal matrix and diamond particles which resist abrasive and cutting forces. The development progresses through a series of steps, exploring methods to process the material, understanding the mechanics of abrasive behavior and optimizing the composite structure to resist abrasive cutting. In processing, infiltration casting under gas pressure has been applied to molten aluminum to obtain a significant penetration of the metal into a preform of diamond particles. Different diamond particle sizes were used with different surface modifications (coated/uncoated), and to compare resulting composites with the same particle sizes. Al-1 wt.% Mg as a matrix alloy was utilised to investigate the possible effect of Mg on bonding phases during the infiltration process. The mechanical behavior and microstructure of the materials produced have been characterised. These tests showed that the surface modification of the diamond particles with a reactive material (Ti-coating) has an important role for enhancing the bonding between the aluminium matrix and diamond reinforcement as apparent under SEM observation. The effect of this improved bond is seen in the cutting resistance of the material.

Keywords: aluminium, composites, diamond, Ti-coated, tribology

Procedia PDF Downloads 241

Authors: M. Masłowski, M. Zaborski

Abstract:

Magnetorheological elastomer composites based on micro- and nano-sized Fe3O4 magnetoactive fillers in silicone rubber are reported and studied. To improve the dispersion of applied fillers in polymer matrix, ionic liquids such as 1-ethyl-3-methylimidazolium diethylphosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoromethanesulfonate,1-butyl-3-methylimidazolium tetrafluoroborate, trihexyltetradecylphosphonium chloride were added during the process of composites preparation. The method of preparation process influenced the specific properties of MREs (isotropy/anisotropy), similarly to ferromagnetic particles content and theirs quantity. Micro and non-sized magnetites were active fillers improving the mechanical properties of elastomers. They also changed magnetic properties and reinforced the magnetorheological effect of composites. Application of ionic liquids as dispersing agents influenced the dispersion of magnetic fillers in the elastomer matrix. Scanning electron microscopy images used to observe magnetorheological elastomer microstructures proved that the dispersion improvement had a significant effect on the composites properties. Moreover, the particles orientation and their arrangement in the elastomer investigated by vibration sample magnetometer showed the correlation between MRE microstructure and their magnetic properties.

Keywords: magnetorheological elastomers, iron oxides, ionic liquids, dispersion

Procedia PDF Downloads 305

Authors: A. Evcin, N. Çiçek Bezir, R. Duman, N. Duman

Abstract:

Nowadays, a great concern is placed on the harmfulness of ultraviolet radiation (UVR) which attacks human bodies. Nanocarbon materials, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene, have been considered promising alternatives to shielding materials because of their excellent electrical conductivities, very high surface areas and low densities. In the present work, carbon nanofibers have been synthesized from solutions of Polyacrylonitrile (PAN)/ N,N-dimethylformamide (DMF) by electrospinning method. The carbon nanofibers have been stabilized by oxidation at 250 °C for 2 h in air and carbonized at 750 °C for 1 h in H2/N2. We present the fabrication and characterization of transparent and ultraviolet (UV) shielding CNF/polymer composites. The content of CNF filler has been varied from 0.2% to 0.6 % by weight. UV Spectroscopy has been performed to study the effect of composition on the transmittance of polymer composites.

Keywords: electrospinning, carbon nanofiber, characterization, composites, nanofiber, ultraviolet radiation

Procedia PDF Downloads 186

Authors: Daniel Karthik, Vijay Baheti, Jiri Militky, Sundaramurthy Palanisamy

Abstract:

Fibre based nano particles are presently considered as one of the potential filler materials for the improvement of mechanical and physical properties of polymer composites. Due to high matrix-filler interfacial area there will be uniform and homogeneous dispersion of nanoparticles. In micro/nano filler reinforced composites, resin material is usually tailored by organic or inorganic nanoparticles to have improved matrix properties. The objective of this study was to compare the potential of reinforcement of different organic and inorganic micro/nano fillers in epoxy composites. Industrial and agricultural waste of fibres like Agave Americana, cornhusk, jute, basalt, carbon, glass and fly ash was utilized to prepare micro/nano particles. Micro/nano particles were obtained using high energy planetary ball milling process in dry condition. Milling time and ball size were kept constant throughout the ball milling process. Composites were fabricated by hand lay method. Particle loading was kept constant to 3% wt. for all composites. In present study, loading of fillers was selected as 3 wt. % for all composites. Dynamic mechanical properties of the nanocomposite films were performed in three-point bending mode with gauge length and sample width of 50 mm and 10 mm respectively. The samples were subjected to an oscillating frequency of 1 Hz, 5 Hz and 10 Hz and 100 % oscillating amplitude in the temperature ranges of 30°C to 150°C at the heating rate of 3°C/min. Damping was found to be higher with the jute composites. Amongst organic fillers lowest damping factor was observed with Agave Americana particles, this means that Agave americana fibre particles have betters interface adhesion with epoxy resin. Basalt, fly ash and glass particles have almost similar damping factors confirming better interface adhesion with epoxy.

Keywords: ball milling, damping factor, matrix-filler interface, particle reinforcements

Procedia PDF Downloads 243

Authors: Azeez Shaik, Yagnik Kalariya, Amit Salvi

Abstract:

High-performance requirements and emission norms were forcing the automobile industry to opt for lightweight materials which improve the fuel efficiency and absorb energy during crash applications. In such scenario, the woven fabric composites are providing better energy absorption compared to metals. Woven fabric composites have a repetitive unit cell (RUC) and the mechanical properties of these materials are highly dependent on RUC. This work investigates the importance of detailed modelling of the RUC, the size effects associated and the mitigation techniques to avoid them using Finite element analysis approach.

Keywords: repetitive unit cell, representative volume element, size effects, cohesive zone, finite element analysis

Procedia PDF Downloads 218

Authors: Konstantinos Sotiriadis, Olesia Mikhailova

Abstract:

In the present work, fly ash geopolymer based composites including polyester (PES) waste were studied. Specimens of three compositions were prepared: (a) fly ash geopolymer with 5% PES waste, (b) fly ash geopolymer mortar with 5% PES waste, (c) fly ash geopolymer mortar with 6.25% PES waste. Compressive and bending strength measurements, water absorption test and determination of thermal conductivity coefficient were performed. The results showed that the addition of sand in a mixture of geopolymer with 5% PES content led to higher compressive strength, while it increased water absorption and reduced thermal conductivity coefficient. The increase of PES addition in geopolymer mortars resulted in a more dense structure, indicated by the increase of strength and thermal conductivity and the decrease of water absorption.

Keywords: fly ash, geopolymers, polyester waste, composites

Procedia PDF Downloads 394

Authors: Petra Gajdačová

Abstract:

The presented research deals with a complex evaluation of after-harvest remnants utilization for particleboard production. Agricultural crops that are in the Czech Republic widely grown are in the scope of interest. Researches dealing with composites from agricultural rests solved mostly physical and mechanical properties of produced materials. For the commercialization of these results, however, one another step is essential. It is needed to evaluate the composites production from agricultural rests more comprehensive, take into account all aspects that affect their production, not only material characteristics of produced composites. In this study, descriptive, comparative and synthesis methods were used. Results of this research include a supply stability forecast, technical and technological differences of production of particleboards from agricultural rests and quantification of an economical potential of the agricultural rests.

Keywords: agricultural crops, annual plant, composite material, particleboard

Procedia PDF Downloads 162

Authors: Tigist Girma Kedane

Abstract:

The purpose of this paper is to evaluate the properties of Ethiopian bamboo fiber polymer composites for headliner materials in the automobile industry. Accurate evaluation of its mechanical properties is thus critical for predicting its behavior during a vehicle's interior impact assessment. Conventional headliner materials are higher in weight, nonbiodegradable, expensive in cost, and unecofriendly during processing compared to the current researched materials. Three representatives of bamboo plants are harvested in three regions of bamboo species, three groups of ages, and two harvesting months. The statistical analysis was performed to validate the significant difference between the mean strength of bamboo ages, harvesting seasons, and bamboo species. Two-year-old bamboo fibers have the highest mechanical properties in all ages and November has higher mechanical properties compared to February. Injibara and Kombolcha have the highest and the lowest mechanical properties of bamboo fibers, respectively. Bamboo fiber epoxy composites have higher mechanical properties compared to bamboo fiber polypropylene composites. The flexural strength of bamboo fibre polymer composites has higher properties compared to tensile strength. Ethiopian bamboo fibers and their polymer composites have the best mechanical properties for the composite industry, which is used for headliner materials in the automobile industry compared to conventional headliner materials.

Keywords: bampoo species, culm age, harvesting seasons, mechanical properties, polymer composite

Procedia PDF Downloads 28

Authors: Atilla Evcin, Bahri Ersoy, Süleyman Akpınar, I. Sinan Atlı

Abstract:

Ceramic, polymer and composite nanofibers are nowadays begun to be utilized in many fields of nanotechnology. By the means of dimensions, these fibers are as small as nano scale but because of having large surface area and microstructural characteristics, they provide unique mechanic, optical, magnetic, electronic and chemical properties. In terms of nanofiber production, electrospinning has been the most widely used technique in recent years. In this study, carbon nanofibers have been synthesized from solutions of Polyacrylonitrile (PAN)/ N,N-dimethylformamide (DMF) by electrospinning method. The carbon nanofibers have been stabilized by oxidation at 250 °C for 2 h in air and carbonized at 750 °C for 1 h in H2/N2. Images of carbon nanofibers have been taken with scanning electron microscopy (SEM). The images have been analyzed to study the fiber morphology and to determine the distribution of the fiber diameter using FibraQuant 1.3 software. Then polymer composites have been produced from mixture of carbon nanofibers and silicone polymer. The final polymer composites have been characterized by X-ray diffraction method and scanning electron microscopy (SEM) energy dispersive X-ray (EDX) measurements. These results have been reported and discussed. At result, homogeneous carbon nanofibers with 100-167 nm of diameter were obtained with optimized electrospinning conditions.

Keywords: electrospinning, characterization, composites, nanofiber

Procedia PDF Downloads 368

Authors: R. Naveen, E. Vanitha, S. Gayathri

Abstract:

The use of Sandwich composite materials in aerospace and civil infrastructure application has been increasing especially due to their enormously low weight that leads to a reduction in the total weight and fuel consumption, high flexural and transverse shear stiffness, and corrosion resistance. The essential properties of sandwich materials vary according to the application area of the structure. The objectives of this study are to identify the mechanical behaviour and failure mechanisms of sandwich structures made of bamboo, V- board and metal (Aluminium as face sheet and Foam as Core material). The three-point bending test and UTM (Universal testing machine) experimental tests are done for three specimens for each type of sandwich composites. From the experiment results of three sandwich composites, bamboo shows high Young’s modulus of elasticity and low density.

Keywords: bamboo sandwich composite, metal sandwich composite, sandwich composite, v-board sandwich composite

Procedia PDF Downloads 229

Authors: T. P. Sathishkumar, P. Navaneethakrishnan

Abstract:

The research work investigates the variation of tensile properties for the sansevieria ehrenbergii fiber (SEF) and SEF reinforced polyester composites respect to various water absorption time. The experiments were conducted according to ATSM D3379-75 and ASTM D570 standards. The percentage of water absorption for composite specimens was measured according to ASTM D570 standard. The fiber of SE was cut in to 30 mm length for preparation of the composites. The simple hand lay-up method followed by compression moulding process adopted to prepare the randomly oriented SEF reinforced polyester composites at constant fiber weight fraction of 40%. The surface treatment was done on the SEFs with various chemicals such as NaOH, KMnO4, Benzoyl Peroxide, Benzoyl Chloride and Stearic Acid before preparing the composites. NaOH was used for pre-treatment of all other chemical treatments. The morphology of the tensile fractured specimens studied using the Scanning Electron Microscopic. The tensile strength of the SEF and SEF reinforced polymer composites were carried out with various water absorption time such as 4, 8, 12, 16, 20 and 24 hours respectively. The result shows that the tensile strength was drop off with increase in water absorption time for all composites. The highest tensile property of raw fiber was found due to lowest moistures content. Also the chemical bond between the cellulose and cementic materials such as lignin and wax was highest due to lowest moisture content. Tensile load was lowest and elongation was highest for the water absorbed fibers at various water absorption time ranges. During this process, the fiber cellulose inhales the water and expands the primary and secondary fibers walls. This increases the moisture content in the fibers. Ultimately this increases the hydrogen cation and the hydroxide anion from the water. In tensile testing, the water absorbed fibers shows highest elongation by stretching of expanded cellulose walls and the bonding strength between the fiber cellulose is low. The load carrying capability was stable at 20 hours of water absorption time. This could be directly affecting the interfacial bonding between the fiber/matrix and composite strength. The chemically treated fibers carry higher load and lower elongation which is due to removal of lignin, hemicellulose and wax content. The water time absorption decreases the tensile strength of the composites. The chemically SEF reinforced composites shows highest tensile strength compared to untreated SEF reinforced composites. This was due to highest bonding area between the fiber/matrix. This was proven in the morphology at the fracture zone of the composites. The intra-fiber debonding was occurred by water capsulation in the fiber cellulose. Among all, the tensile strength was found to be highest for KMnO4 treated SEF reinforced composite compared to other composites. This was due to better interfacial bonding between the fiber-matrix compared to other treated fiber composites. The percentage of water absorption of composites increased with time of water absorption. The percentage weight gain of chemically treated SEF composites at 4 hours to zero water absorption are 9, 9, 10, 10.8 and 9.5 for NaOH, BP, BC, KMnO4 and SA respectively. The percentage weight gain of chemically treated SEF composites at 24 hours to zero water absorption 5.2, 7.3, 12.5, 16.7 and 13.5 for NaOH, BP, BC, KMnO4 and SA respectively. Hence the lowest weight gain was found for KMnO4 treated SEF composites by highest percentage with lowest water uptake. However the chemically treated SEF reinforced composites is possible materials for automotive application like body panels, bumpers and interior parts, and household application like tables and racks etc.

Keywords: fibres, polymer-matrix composites (PMCs), mechanical properties, scanning electron microscopy (SEM)

Procedia PDF Downloads 388

Authors: C. S. Paglia, E. Ginercordero, A. Jornet

Abstract:

Environmental pollution, along with the depletion of natural resources, is among the most serious global challenges in our times. The construction industry is one of the sectors where a relevant reduction of the environmental impact can be achieved. Thus, the cement production will play a key role in sustainability, by reducing the CO₂ emissions and energy consumption and by increasing the durability of the structures. A large number of investigations have been carried out on blended cements, but it exists a lack of information on the Portland cement limestone - silica fume system. Mortar blends are optimized in the mix proportions for the different ingredients, in particular for the dosage of the silica fume. Portland cement and the new binder-based systems are compared with respect to the fresh mortar properties, the mechanical and the durability behaviour of the hardened specimens at 28 and 90 days. The use of this new binder combination exhibits an interesting hydration development with time and maintain the conventional characteristics of Portland cementitious material. On the other hand, it will be necessary to reproduce the Portland Limestone Cement-silica fume system within the concrete. A reduction of the CO₂ production, energy consumption, and a reasonable service life of the concrete structures, including a maintenance free period, will all contribute to a better environment.

Keywords: binder, cement, limestone, silica fume

Procedia PDF Downloads 90

Authors: Ali Garba Danjani, Abdulrasheed Halliru Usman

Abstract:

Due to the rapidly increasing biological applications and antibacterial properties of versatile chitosan composites, the effects of chitosan/polyvinyl chloride composites film were investigated. Chitosan/polyvinyl chloride films were prepared by a casting method. Polyethylene glycol (PEG) was used as a plasticizer in the blending stage of film preparation. Characterizations of films were done by Scanning Electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and thermogravimetric analyzer (TGA). Chitosan composites incorporation enhanced the antibacterial activity of chitosan films against Escherichia coli and Staphylococcus aureus. The composite film produced is proposed as packaging or coating material because of its flexibility, antibacterial efficacy, and good mechanical strength.

Keywords: chitosan, polymeric nanocomposites, antibacterial activity, polymer blend

Procedia PDF Downloads 62

Authors: Abdul Hakim Abdullah, Mohamad Syafiq Abdul Khadir

Abstract:

In present investigations, thermal behaviours of Arenga pinnata fibres prior and after alkaline treatment were studied. The alkaline treatments were applied on the Arenga pinnata fibres by immersing in the alkaline solution, 6% sodium hydroxide (NaOH). Using hand lay-out technique, composites were fabricated at 20% and 40% by Arenga pinnata fibres weight contents. The thermal behaviours of both untreated and treated composites were determined by employing Dynamic Mechanical Analysis (DMA). The results show that the TAP owned better results of Storage Modulus (E’), Loss Modulus (E”) and Tan Delta temperatures ranges from 0°C to 60°C.

Keywords: composites, Arenga pinnata fibre, alkaline treatment, dynamic mechanical properties

Procedia PDF Downloads 332

Authors: Paul Essel, Eric T. Glover, Gustav Gbeddy, Yaw Adjei-Kyereme, Abdallah M. A. Dawood, Evans M. Ameho, Emmanuel A. Aberikae

Abstract:

Radioactive materials mainly in the form of Sealed Radioactive Sources are being used in various sectors (medicine, agriculture, industry, research, and teaching) for the socio-economic development of Ghana. The use of these beneficial radioactive materials has resulted in an inventory of Disused Sealed Radioactive Sources (DSRS) in storage. Most of the DSRS are legacy/historic sources which cannot be returned to their manufacturer or country of origin. Though small in volume, DSRS can be intensively radioactive and create a significant safety and security liability. They need to be managed in a safe and secure manner in accordance with the fundamental safety objective. The Radioactive Waste Management Center (RWMC) of the Ghana Atomic Energy Commission (GAEC) is currently storing a significant volume of DSRS. The initial activities of the DSRS range from 7.4E+5 Bq to 6.85E+14 Bq. If not managed properly, such DSRS can represent a potential hazard to human health and the environment. Storage is an important interim step, especially for DSRS containing very short-lived radionuclides, which can decay to exemption levels within a few years. Long-term storage, however, is considered an unsustainable option for DSRS with long half-lives hence the need for a disposal facility. The GAEC intends to use the International Atomic Energy Agency’s (IAEA’s) Borehole Disposal System (BDS) to provide a safe, secure, and cost-effective disposal option to dispose of its DSRS in storage. The proposed site for implementation of the BDS is on the GAEC premises at Kwabenya. The site has been characterized to gain a general understanding in terms of its regional setting, its past evolution and likely future natural evolution over the assessment time frame. Due to the long half-lives of some of the radionuclides to be disposed of (Ra-226 with half-life of 1600 years), the engineered barriers of the system must be robust to contain these radionuclides for this long period before they decay to harmless levels. There is the need to assess the safety related functions of the engineered barriers of this disposal system.

Keywords: radionuclides, disposal, radioactive waste, engineered barrier

Procedia PDF Downloads 25

Authors: A. Gürses, Z. Eroğlu, E. Şahin, K. Güneş, Ç. Doğar

Abstract:

In recent years, polymer/clay nanocomposites have generated great interest in the polymer industry as a new type of composite material because of their superior properties, which includes high heat deflection temperature, gas barrier performance, dimensional stability, enhanced mechanical properties, optical clarity and flame retardancy when compared with the pure polymer or conventional composites. The investigation of change of the tensile properties of organoclay/linear low density polyethylene (LLDPE) nanocomposites with the use of Dioctyl terephthalate (DOTP) (as plasticizer) and calcite (as filler) has been aimed. The composites and organoclay synthesized were characterized using the techniques such as XRD, HRTEM and FTIR techniques. The spectroscopic results indicate that platelets of organoclay were well dispersed within the polymeric matrix. The tensile properties of the composites were compared considering the stress-strain curve drawn for each composite and pure polymer. It was observed that the composites prepared by adding the plasticizer at different ratios and a certain amount of calcite exhibited different tensile behaviors compared to pure polymer.

Keywords: linear low density polyethylene, nanocomposite, organoclay, plasticizer

Procedia PDF Downloads 261

Authors: Niloofar Bahramian, Mohammad Atai, Mohammad Reza Naimi-Jamal

Abstract:

Rule of mixtures is the simple analytical model is used to predict various properties of composites before design. The aim of this study was to demonstrate the benefits and limitations of the Rule-of-Mixtures (ROM) for predicting bending modulus of a continuous and unidirectional fiber reinforced composites using in dental applications. The Composites were fabricated from light curing resin (with and without silica nanoparticles) and modified and non-modified fibers. Composite samples were divided into eight groups with ten specimens for each group. The bending modulus (flexural modulus) of samples was determined from the slope of the initial linear region of stress-strain curve on 2mm×2mm×25mm specimens with different designs: fibers corona treatment time (0s, 5s, 7s), fibers silane treatment (0%wt, 2%wt), fibers volume fraction (41%, 33%, 25%) and nanoparticles incorporation in resin (0%wt, 10%wt, 15%wt). To study the fiber and matrix interface after fracture, single edge notch beam (SENB) method and scanning electron microscope (SEM) were used. SEM also was used to show the nanoparticles dispersion in resin. Experimental results of bending modulus for composites made of both physical (corona) and chemical (silane) treated fibers were in reasonable agreement with linear ROM estimates, but untreated fibers or non-optimized treated fibers and poor nanoparticles dispersion did not correlate as well with ROM results. This study shows that the ROM is useful to predict the mechanical behavior of unidirectional dental composites but fiber-resin interface and quality of nanoparticles dispersion play important role in ROM accurate predictions.

Keywords: bending modulus, fiber reinforced composite, fiber treatment, rule-of-mixtures

Procedia PDF Downloads 231

Authors: Rui Magalhães, Sohel Rana, Raul Fangueiro, Clara Gonçalves, Pedro Nunes, Gustavo Dias

Abstract:

Auxetic fibrous structures and composites with negative Poisson’s ratio (NPR) have huge potential for application in ballistic protection due to their high energy absorption and excellent impact resistance. In the present research, re-entrant lozenge auxetic fibrous structures were produced through weft knitting technology using high performance polyamide and para-aramid fibres. Fabric structural parameters (e.g. loop length) and machine parameters (e.g. take down load) were varied in order to investigate their influence on the auxetic behaviours of the produced structures. These auxetic structures were then impregnated with two types of polymeric resins (epoxy and polyester) to produce composite materials, which were subsequently characterized for the auxetic behaviour. It was observed that the knitted fabrics produced using the polyamide yarns exhibited NPR over a wide deformation range, which was strongly dependant on the loop length and take down load. The polymeric composites produced from the auxetic fabrics also showed good auxetic property, which was superior in case of the polyester matrix. The experimental results suggested that these composites made from the auxetic fibrous structures can be properly designed to find potential use in the body amours for personal protection applications.

Keywords: auxetic fabrics, high performance, composites, energy absorption, impact resistance

Procedia PDF Downloads 226

Authors: Shahril Anuar Bahari, Mohd Azrie Mohd Kepli, Mohd Ariff Jamaludin, Kamarulzaman Nordin, Mohamad Jani Saad

Abstract:

Formaldehyde release from wood-based panel composites can be very toxicity and may increase the risk of human health as well as environmental problems. A new bio-composites product without synthetic adhesive or resin is possible to be developed in order to reduce these problems. Apart from formaldehyde release, adhesive is also considered to be expensive, especially in the manufacturing of composite products. Natural bonded composites can be termed as a panel product composed with any type of cellulosic materials without the addition of synthetic resins. It is composed with chemical content activation in the cellulosic materials. Pulp and paper making method (chemical pulping) was used as a general guide in the composites manufacturing. This method will also generally reduce the manufacturing cost and the risk of formaldehyde emission and has potential to be used as an alternative technology in fiber composites industries. In this study, the natural bonded bamboo fiber composite was produced from virgin Malaysian bamboo fiber (Bambusa vulgaris). The bamboo culms were chipped and digested into fiber using this pulping method. The black liquor collected from the pulping process was used as a natural binding agent in the composition. Then the fibers were mixed and blended with black liquor without any resin addition. The amount of black liquor used per composite board was 20%, with approximately 37% solid content. The composites were fabricated using a hot press machine at two different board densities, 850 and 950 kg/m³, with two sets of hot pressing time, 25 and 35 minutes. Samples of the composites from different densities and hot pressing times were tested in flexural strength and internal bonding (IB) for strength performance according to British Standard. Modulus of elasticity (MOE) and modulus of rupture (MOR) was determined in flexural test, while tensile force perpendicular to the surface was recorded in IB test. Results show that the strength performance of the composites with 850 kg/m³ density were significantly higher than 950 kg/m³ density, especially for samples from 25 minutes hot pressing time. Strength performance of composites from 25 minutes hot pressing time were generally greater than 35 minutes. Results show that the maximum mean values of strength performance were recorded from composites with 850 kg/m³ density and 25 minutes pressing time. The maximum mean values for MOE, MOR and IB were 3251.84, 16.88 and 0.27 MPa, respectively. Only MOE result has conformed to high density fiberboard (HDF) standard (2700 MPa) in British Standard for Fiberboard Specification, BS EN 622-5: 2006. Microstructure characteristics of composites can also be related to the strength performance of the composites, in which, the observed fiber damage in composites from 950 kg/m³ density and overheat of black liquor led to the low strength properties, especially in IB test.

Keywords: bamboo fiber, natural bonded, black liquor, mechanical tests, microstructure observations

Procedia PDF Downloads 224

Authors: B. Safi, B. Amrane, M. Saidi

Abstract:

The main purpose of this study is to evaluate the reuse of refractory brick wastes (RBW) as a supplementary cementitious materials (by a total replacement of silica fume) to produce a high performance fiber-reinforced concrete (HPFRC). This work presents an experimental study on the formulation and physico-mechanical characterization of ultra high performance fiber reinforced concretes based on three types of refractory brick wastes. These have been retrieved from the manufacturing unit of float glass MFG (Mediterranean Float Glass) after their use in the oven basin (ie d. they are considered waste unit). Three compositions of concrete (HPFRC) were established based on three types of refractory brick wastes (finely crushed), with the dosage of each type of bricks is kept constant, similar the dosage of silica fume used for the control concrete. While all the other components and the water/binder ratio are maintained constant with the same quantity of the superplasticizer. The performance of HPFRC, were evaluated by determining the essential characteristics of fresh and hardened concrete.

Keywords: refractory bricks, concrete, fiber, fluidity, compressive strength, tensile strength

Procedia PDF Downloads 570

Authors: Ganiyu I. Lawal, Olatunde I. Sekunowo, Stephen I. Durowaye

Abstract:

Composites depending on the nature of their constituents and mode of production are regarded as one of the advanced materials that drive today’s technology. This paper attempts a short review of the subject matter with a general aim of pushing to the next level the frontier of knowledge as it impacts the technology of nano-particles manufacturing. The objectives entail an effort to; aggregate recent research efforts in this field, analyse research findings and observations, streamline research efforts and support industry in taking decision on areas of fund deployment. It is envisaged that this work will serve as a quick hand-on compendium material for researchers in this field and a guide to relevant government departments wishing to fund a research whose outcomes have the potential of improving the nation’s GDP.

Keywords: advanced materials, composites, mechanical properties, nano-particles

Procedia PDF Downloads 251

Authors: Ehsan Alishahi, Chuang Deng

Abstract:

Commercial applications of bulk metallic glasses (BMGs) were restricted due to the sudden brittle failure mode which was the main drawback in these new class of materials. Therefore, crystalline-amorphous (C-A) composites were introduced as a toughening strategy in BMGs. In spite of numerous researches in the area of metallic C-A composites, the fundamental structure-property relation in these composites that are not exactly known yet. In this study, it is aimed to investigate the fundamental properties of crystalline-amorphous interface in a model system of Cu/CuZr by using molecular dynamics simulations. Several parameters including interface energy and mechanical properties were investigated by means of atomic models and employing Embedded Atom Method (EAM) potential function. It is found that the crystalline-amorphous interfacial energy weakly depends on the orientation of the crystalline layer, which is in stark contrast to that in a regular crystalline grain boundary. Additionally, the results showed that the interface controls the yielding of the crystalline-amorphous composites during uniaxial tension either by serving as sources for dislocation nucleation in the crystalline layer or triggering local shear transformation zones in amorphous layer. The critical resolved shear stress required to nucleate the first dislocation is also found to strongly depend on the crystalline orientation. Furthermore, it is found that the interaction between dislocations and shear localization at the crystalline-amorphous interface oriented in different directions can lead to a change in the deformation mode. For instance, while the dislocation and shear banding are aligned to each other in {0 0 1} interface plane, the misorientation angle between these failure mechanisms causing more homogeneous deformation in {1 1 0} and {1 1 1} crystalline-amorphous interfaces. These results should help clarify the failure mechanism of crystalline-amorphous composites under various loading conditions.

Keywords: crystalline-amorphous, composites, orientation, plasticity

Procedia PDF Downloads 265

Authors: A. D'Alessandro, F. Ubertini, A. L. Materazzi

Abstract:

In the field of civil engineering, Structural Health Monitoring is a topic of growing interest. Effective monitoring instruments permit the control of the working conditions of structures and infrastructures, through the identification of behavioral anomalies due to incipient damages, especially in areas of high environmental hazards as earthquakes. While traditional sensors can be applied only in a limited number of points, providing a partial information for a structural diagnosis, novel transducers may allow a diffuse sensing. Thanks to the new tools and materials provided by nanotechnology, new types of multifunctional sensors are developing in the scientific panorama. In particular, cement-matrix composite materials capable of diagnosing their own state of strain and tension, could be originated by the addition of specific conductive nanofillers. Because of the nature of the material they are made of, these new cementitious nano-modified transducers can be inserted within the concrete elements, transforming the same structures in sets of widespread sensors. This paper is aimed at presenting the results of a research about a new self-sensing nanocomposite and about the implementation of smart sensors for Structural Health Monitoring. The developed nanocomposite has been obtained by inserting multi walled carbon nanotubes within a cementitious matrix. The insertion of such conductive carbon nanofillers provides the base material with piezoresistive characteristics and peculiar sensitivity to mechanical modifications. The self-sensing ability is achieved by correlating the variation of the external stress or strain with the variation of some electrical properties, such as the electrical resistance or conductivity. Through the measurement of such electrical characteristics, the performance and the working conditions of an element or a structure can be monitored. Among conductive carbon nanofillers, carbon nanotubes seem to be particularly promising for the realization of self-sensing cement-matrix materials. Some issues related to the nanofiller dispersion or to the influence of the nano-inclusions amount in the cement matrix need to be carefully investigated: the strain sensitivity of the resulting sensors is influenced by such factors. This work analyzes the dispersion of the carbon nanofillers, the physical properties of the fresh dough, the electrical properties of the hardened composites and the sensing properties of the realized sensors. The experimental campaign focuses specifically on their dynamic characterization and their applicability to the monitoring of full-scale elements. The results of the electromechanical tests with both slow varying and dynamic loads show that the developed nanocomposite sensors can be effectively used for the health monitoring of structures.

Keywords: carbon nanotubes, self-sensing nanocomposites, smart cement-matrix sensors, structural health monitoring

Procedia PDF Downloads 205

Authors: Benny Alexander, Ikhlashia N. Fadhilah, Muhammad R. Pasha, Michelle Julia, Anne Z. Syahrial

Abstract:

Brake shoe is a component that serves to reduce speed or stop the train's speed by utilizing the friction force. Generally, the material used as a brake shoe is cast iron, where cast iron itself is a heavy, expensive, and easily worn material. Aluminum matrix composites are one of candidates for the cast iron replacement material as the basic material for brake shoe. The matrix in the composite used is Aluminum AC4B. Reinforcement used in aluminum matrix composites is nano-alumina, where the use of nano-alumina of 0.25%, 0.3%, 0.35%, 0.4%, and 0.5% volume fraction will be tested. The sample is made using the stir casting method; then, it will be tested mechanically. The use of nano-alumina as a reinforcement will increase the strength of the matrix. SEM (scanning electron microscopy) testing is used to test the distribution of reinforcing particles due to stirring. Therefore, the addition of nano-alumina will improve AC4B aluminum matrix composites.

Keywords: aluminium matrix composites, brake shoe application, stir casting, nano-alumina

Procedia PDF Downloads 103

Authors: Băilă Diana Irinel, Păcurar Răzvan, Păcurar Ancuța

Abstract:

Although the volumes of fibre reinforced polymer composites (FRPs) used for aircraft applications is a relatively small percentage of total use, the materials often find their most sophisticated applications in this industry. In aerospace, the performance criteria placed upon materials can be far greater than in other areas – key aspects are light-weight, high-strength, high-stiffness, and good fatigue resistance. Composites were first used by the military before the technology was applied to commercial planes. Nowadays, composites are widely used, and this has been the result of a gradual direct substitution of metal components followed by the development of integrated composite designs as confidence in FRPs has increased. The airplane uses a range of components made from composites, including the fin and tailplane. In the last years, composite materials are increasingly used in automotive applications due to the improvement of material properties. In the aerospace and automotive sector, the fuel consumption is proportional to the weight of the body of the vehicle. A minimum of 20% of the cost can be saved if it used polymer composites in place of the metal structures and the operating and maintenance costs are alco very low. Glass fiber-epoxy composites are widely used in the making of aircraft and automobile body parts and are not only limited to these fields but also used in ship building, structural applications in civil engineering, pipes for the transport of liquids, electrical insulators in reactors. This article was establish the high-performance of composite material, a type glass-epoxy used in automotive and aeronautic domains, concerning the tensile and flexural tests and SEM analyzes.

Keywords: glass-epoxy composite, traction and flexion tests, SEM analysis, acoustic emission (AE) signals

Procedia PDF Downloads 73