Search results for: adhesive

Authors: Maryam Hamedanlou, Shahla Hajializadeh

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The transdermal drug delivery system is one of the types of novel drug delivery system that the drug is absorbed into the skin. The major considerations for designing and producing transdermal patch are small size, suitable drug release and good adhering. In this study, drug-in-adhesive transdermal patch contained non-steroidal anti-inflammatory ketoprofen is prepared. Also, the effect of non-woven fabric and plastic backing layers on adhesion properties is assessed. The results of the test, demonstrated the use of plastic backing layer increases tack and peel rather than non-woven fabric type. The balance tack with plastic backing layer patch is 6.7 (N/mm2), and the fabric one is 3.8 (N/mm2), and their peel is 9.2 (N/25mm) and 8.3 (N/25mm) by arrangement.

Keywords: transdermal drug delivery system, single layer patch of ketoprofen, plastic layer, fabric backing layer

Procedia PDF Downloads 220

Authors: Paul Onyegbule, Harjit Singh

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Vacuum glazing is an innovative transparent thermal insulator that has application in high performance window, especially in renewable energy. Different materials as well as sealing methods have been adopted to seal windows with different temperatures. The impact of temperatures on sealing layers has been found to have significant effects on the microstructure of the seal. This paper seeks to investigate the effects of sealing materials specifically glass powder and flux compound (borax) for vacuum glazing. The findings of the experiment conducted show that the sealing material was rigid with some leakage around the edge, and we found that this could be stopped by enhancing the uniformity of the seal within the periphery. Also, we found that due to the intense tensile stress from the oven surface temperature of the seal at 200 ⁰C, a crack was observed at the side of the glass. Based on the above findings, this study concludes that a glass powder with a lower melting temperature of below 250 ⁰C with the addition of an adhesive (borax flux) should be used for future vacuum seals.

Keywords: double glazed windows, U-value, heat loss, borax powder, edge seal

Procedia PDF Downloads 191

Authors: Mohammed A. Sakr, Tarek M. Khalifa, Walid N. Mansour

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Fiber reinforced polymer (FRP) installation is a very effective way to repair and strengthen structures that have become structurally weak over their life span. This technique attracted the concerning of researchers during the last two decades. This paper presents a simple uniaxial nonlinear finite element model (UNFEM) able to accurately estimate the load-carrying capacity, different failure modes and the interfacial stresses of reinforced concrete (RC) continuous beams flexurally strengthened with externally bonded FRP plates on the upper and lower fibers. Results of the proposed finite element (FE) model are verified by comparing them with experimental measurements available in the literature. The agreement between numerical and experimental results is very good. Considering fracture energy of adhesive is necessary to get a realistic load carrying capacity of continuous RC beams strengthened with FRP. This simple UNFEM is able to help design engineers to model their strengthened structures and solve their problems.

Keywords: continuous beams, debonding, finite element, fibre reinforced polymer

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Authors: W. F. Ribeiro, J. L. N. Góes

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The industrial process adds to engineering wood products features absent in solid wood, with homogeneous structure and reduced defects, improved physical and mechanical properties, bio-deterioration, resistance and better dimensional stability, improving quality and increasing the reliability of structures wood. These features combined with using fast-growing trees, make them environmentally ecological products, ensuring a strong consumer market. The wood I-joists are manufactured by the industrial profiles bonding flange and web, an important aspect of the production of wooden I-beams is the adhesive joint that bonds the web to the flange. Adhesives can effectively transfer and distribute stresses, thereby increasing the strength and stiffness of the composite. The objective of this study is to evaluate different resins in a shear strain specimens with the aim of analyzing the most efficient resin and possibility of using national products, reducing the manufacturing cost. First was conducted a literature review, where established the geometry and materials generally used, then established and analyzed 8 national resins and produced six specimens for each.

Keywords: engineered wood products, structural resin, wood i-joist, Pinus taeda

Procedia PDF Downloads 246

Authors: Othman S. Alsheraida, Sherif El-Gamal

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Fiber Reinforced Polymers (FRP) is a composite material with exceptional properties that are capable of replacing conventional steel reinforcement in reinforced and pre-stressed concrete structures. However, the main obstacle for their wide use in the pre-stressed concrete application is the anchorage system. Due to the weakness of FRP in the transverse direction, the pre-stressing capacity of FRP bars is limited. This paper investigates the modification of the conventional wedge anchorage system to be used for stressing of FRP bars in pre-stressed applications. Epoxy adhesive material with glass FRP (GFRP) bars and conventional steel wedge were used in this paper. The GFRP bars are encased with epoxy at the anchor zone and the wedge system was used in the pull-out test. The results showed a loading capacity of 47.6 kN which is 69% of the bar ultimate capacity. Additionally, nylon wedge was made with the same dimensions of the steel wedge and tested for GFRP bars without epoxy layer. The nylon wedge showed a loading capacity of 19.7 kN which is only 28.5% of the ultimate bar capacity.

Keywords: anchorage, concrete, epoxy, frp, pre-stressed

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Authors: Jason Ting Jing Cheng, Lee Foo Wei, Yew Ming Kun, Mo Kim Hung, Yip Chun Chieh

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This research delves into the structural characteristics of distinct construction material, rubberized lightweight foam concrete (RLFC) wall panels, which have been developed as a sustainable alternative for the construction industry. These panels are engineered with a RLFC core, possessing a density of 1150 kg/m3, which is specifically formulated to bear structural loads. The core is enveloped with high-strength fiber cement boards, selected for their superior load-bearing capabilities, and enhanced flexural strength when compared to conventional concrete. A thin bed adhesive, known as TPS, is employed to create a robust bond between the RLFC core and the fiber cement cladding. This study underscores the potential of RLFC wall panels as a viable and eco-friendly option for modern building construction, offering a combination of structural efficiency and environmental benefits.

Keywords: structural performance, rubberized concrete wall panel, fiber cement board, insulation performance

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Authors: Abdullah Bilal Ozturk, Nil Acarali, Hediye Irem Ozgunduz, Hava Gizem Kandilci, Hanifi Sarac

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In this study, zeolite, shellac and different boron chemicals were used as additive to dye and effects were comprehensively investigated. Considering previous studies additive materials that had not used before were determined for produce dye with physical properties. Literature research about the materials provides determining easily sufficient amount of additive materials. Accessible of additives or yearly production amounts are become important issue at selection of materials. Zeolite and boron chemicals are suitable selection in that easy access and has large amount of production in our country. Previous research about boron chemicals shows they have flame retardant effect on textile materials besides numerous usage areas. Also, from previous research, shellac was used widely for protection and insulation of metallic materials. Zeolite added to dye to increase adhesive effect of dye. In this study, corrosion tests were applied to find out if there are positive effects of zeolite, shellac, and boron chemicals to dye’s physical properties.

Keywords: dye, corrosion, zeolite, shellac, boron

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Authors: Bhaumik Merchant, Ajay Gelot

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Concrete is good in compression but if any type of strain applied to it, it starts to fail. Where the steel is good tension, it can bear the deflection up to its elastic limits. This project is based on behavior of engineered cementitious composited (ECC) when it is replaced with the different amount of Polyvinyl Alcohol (PVA) Fibers. As for research, PVA fibers is used with cementitious up to 2% to evaluate the optimum amount of fiber on which we can find the maximum compressive, tensile and flexural strength. PVA is basically an adhesive which is used to formulate glue. Generally due to excessive loading, cracks develops which concludes to successive damage to the structural component. In research plasticizer is used to increase workability. With the help of optimum amount of PVA fibers, it can limit the crack widths up to 60µm to 100µm. Also can be used to reduce resources and funds for rehabilitation of structure. At the starting this fiber concrete can be double the cost as compare to conventional concrete but as it can amplify the duration of structure, it will be less costlier than the conventional concrete.

Keywords: compressive strength, engineered cementitious composites, flexural strength, polyvinyl alcohol fibers, rehabilitation of structures

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Authors: Yashvir Singh

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Around the globe, there is demand for the development of bio-based lubricant which will be biodegradable, non -toxic and environmental friendly. This paper outlines the friction and wear characteristics of Pongamia oil (PO) contaminated bio-lubricant by using pin-on-disc tribometer. To formulate the bio-lubricants, PO was blended in the ratios 15, 30 and 50% by volume with the base lubricant SAE 20 W 40. Tribological characteristics of these blends were carried out at 3.8 m/s sliding velocity and loads applied were 50, 100, 150 N. Experimental results showed that the lubrication regime that occurred during the test was boundary lubrication while the main wear mechanisms were abrasive and the adhesive wear. During testing, the lowest wear was found with the addition of 15% PO, and above this contamination, the wear rate was increased considerably. With increase in load, viscosity of all the bio-lubricants increases and meets the ISO VG 100 requirement at 40 ^oC except PB 50. The addition of PO in the base lubricant acted as a very good lubricant additive which reduced the friction and wear scar diameter during the test. It has been concluded that the PB 15 can act as an alternative lubricant to increase the mechanical efficiency at 3.8 m/s sliding velocity and contribute in reduction of dependence on the petroleum based products.

Keywords: friction, load, pongamia oil, sliding velocity, wear

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Authors: M. Dehghan, R. Al-Mahaidi, I. Sbarski

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An industrial epoxy adhesive used in Carbon Fiber Reinforced Polymer (CFRP)-strengthening systems was modified by dispersing multi-walled carbon nanotubes (MWCNTs). Nanocomposites were fabricated using solvent-assisted dispersion method and ultrasonic mixing. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and tensile tests were conducted to study the effect of nanotubes dispersion on the thermal and mechanical properties of the epoxy composite. Experimental results showed a substantial enhancement in the decomposition temperature and tensile properties of epoxy composite, while, the glass transition temperature (Tg) was slightly reduced due to the solvent effect. The morphology of the epoxy nanocomposites was investigated by SEM. It was proved that using solvent improves the nanotubes dispersion. However, at contents higher than 2 wt. %, nanotubes started to re-bundle in the epoxy matrix which negatively affected the final properties of epoxy composite.

Keywords: carbon fiber reinforced polymer, epoxy, multi-walled carbon nanotube, DMA, glass transition temperature

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Authors: Anas Hallak, Latifa Seblini, Juergen Wilde

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In mechatronics or sensor technology, plastic housings are used to protect sensitive components from harmful environmental influences, such as moisture, media, or reactive substances. Connections, preferably in the form of metallic lead-frame structures, through the housing wall are required for their electrical supply or control. In this system, an insufficient connection between the plastic component, e.g., Polyamide66, and the metal surface, e.g., copper, due to the incompatibility is dominating. As a result, leakage paths can occur along with the plastic-metal interface. Since adhesive bonding has been established as one of the most important joining processes and its use has expanded significantly, driven by the development of improved high-performance adhesives and bonding techniques, this technology has been involved in metal-plastic hybrid structures. In this study, an epoxy bonding agent from DELO (DUALBOND LT2266) has been used to improve the mechanical and chemical binding between the metal and the polymer. It is an adhesion promoter with two reaction stages. In these, the first stage provides fixation to the lead frame directly after the coating step, which can be done by UV-Exposure for a few seconds. In the second stage, the material will be thermally hardened during injection molding. To analyze the two reaction stages of the primer, dynamic DSC experiments were carried out and correlated with Fourier-transform infrared spectroscopy measurements. Furthermore, the number of crosslinking bonds formed in the system in each reaction stage has also been estimated by a rheological characterization. Those investigations have been performed with different times of UV exposure: 12, 96 s and in an industrial preferred temperature range from -20 to 175°C. The shear viscosity values of primer have been measured as a function of temperature and exposure times. For further interpretation, the storage modulus values have been calculated, and the so-called Booij–Palmen plot has been sketched. The next approach in this study is the self-healing mechanisms in the hydride system in which the primer should flow into micro-damage such as interface, cracks, inhibit them from growing, and close them. The ability of the primer to flow in and penetrate defined capillaries made in Ultramid was investigated. Holes with a diameter of 0.3 mm were produced in injection-molded A3EG7 plates with 4 mm thickness. A copper substrate coated with the DUALBOND was placed on the A3EG7 plate and pressed with a certain force. Metallographic analyses were carried out to verify the filling grade, which showed an almost 95% filling ratio of the capillaries. Finally, to estimate the self-healing mechanism in metal-plastic hybrid systems, characterizations have been done on a simple geometry with a metal inlay developed by the Institute of Polymer Technology in Friedrich-Alexander-University. The specimens have been modified with tungsten wire which was to be pulled out after the injection molding to create a micro-hole in the specimen at the interface between the primer and the polymer. The capability of the primer to heal those micro-cracks upon heating, pressing, and thermal aging has been characterized through metallographic analyses.

Keywords: hybrid structures, self-healing, thermoplastic housing, adhesive

Procedia PDF Downloads 159

Authors: Yashvir Singh, Amneesh Singla, Swapnil Bhurat

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Around the globe, there is demand for the development of bio-based lubricant which will be biodegradable, non toxic, and environmentally-friendly. This paper outlines the friction and wear characteristics of ponagamia biodiesel contaminated bio-lubricant by using pin-on-disc tribometer. To formulate the bio-lubricants, Ponagamia oil based biodiesel were blended in the ratios 5, 10, and 20% by volume with the base lubricant SAE 20 W 40. Tribological characteristics of these blends were carried out at 2.5 m/s sliding velocity and loads applied were 50, 100, 150 N. Experimental results showed that the lubrication regime that occurred during the test was boundary lubrication while the main wear mechanisms was the adhesive wear. During testing, the lowest wear was found with the addition of 5 and 10% Ponagamia oil based biodiesel, and above this contamination, the wear rate was increased considerably. The addition of 5 and 10% Ponagamia oil based biodiesel with the base lubricant acted as a very good lubricant additive which reduced the friction and wear rate during the test. It has been concluded that the PBO 5 and PBO 10 can act as an alternative lubricant to increase the mechanical efficiency at 2.5 m/s sliding velocity and contribute in reduction of dependence on the petroleum based products.

Keywords: friction, load, pongamia oil blend, sliding velocity, wear

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Authors: W. Oudad, H. Fikirini, K. Boulenouar

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Material fracture by opening (mode I) is not alone responsible for fracture propagation. Many industrial examples show the presence of mode II and mixed mode I + II. In the present work the three-dimensional and non-linear finite element method is used to estimate the performance of the bonded composite repair of metallic aircraft structures by analyzing the plastic zone size ahead of repaired cracks under mixed mode loading. The computations are made according to Von Mises and Tresca criteria. The extension of the plastic zone which takes place at the tip of a crack strictly depends on many variables, such as the yield stress of the material, the loading conditions, the crack size and the thickness of the cracked component, The obtained results show that the presence of the composite patch reduces considerably the size of the plastic zone ahead of the crack. The effects of the composite orientation layup (adhesive properties) and the patch thickness on the plastic zone size ahead of repaired cracks were analyzed.

Keywords: crack, elastic-plastic, J integral, patch, plastic zone

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Authors: Bruno Bacci Fernandes, Stephan Mändl, Ataíde Ribeiro da Silva Junior, José Osvaldo Rossi, Mário Ueda

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Nitrogen implantation in aluminum and its alloys is acquainted for the difficulties in obtaining modified layers deeper than 200 nm. The present work addresses a new method to overcome such a problem; although, the coating with nitrogen and oxygen obtained by plasma immersion ion implantation (PIII) into a 7075 aluminum alloy surface was too shallow. This alloy is commonly used for structural parts in aerospace applications. Such a layer was characterized by secondary ion mass spectroscopy, electron microscopy, and nanoindentation experiments reciprocating wear tests. From the results, one can assume that the wear of this aluminum alloy starts presenting severe abrasive wear followed by an additional adhesive mechanism. PIII produced a slight difference, as shown in all characterizations carried out in this work. The results shown here can be used as the scientific basis for further nitrogen PIII experiments in aluminum alloys which have the goal to produce thicker modified layers or to improve their surface properties.

Keywords: aluminum alloys, plasma immersion ion implantation, tribological properties, hardness, nanofatigue

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Authors: Nader H. Ghareeb, Mohamed S. Gaith, Sayed M. Soleimani

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In modern engineering, weight optimization has a priority during the design of structures. However, optimizing the weight can result in lower stiffness and less internal damping, causing the structure to become excessively prone to vibration. To overcome this problem, active or smart materials are implemented. The coupled electromechanical properties of smart materials, used in the form of piezoelectric ceramics in this work, make these materials well-suited for being implemented as distributed sensors and actuators to control the structural response. The smart structure proposed in this paper is composed of a cantilevered steel beam, an adhesive or bonding layer, and a piezoelectric actuator. The static deflection of the structure is derived as function of the piezoelectric voltage, and the outcome is compared to theoretical and experimental results from literature. The relation between the voltage and the piezoelectric moment at both ends of the actuator is also investigated and a reduced finite element model of the smart structure is created and verified. Finally, a linear controller is implemented and its ability to attenuate the vibration due to the first natural frequency is demonstrated.

Keywords: active linear control, lyapunov stability theorem, piezoelectricity, smart structure, static deflection

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Authors: R. Narasimha Rao, Ch. Sri Chaitanya

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Syntactic foams are closed-cell foams with high specific strength and high compression strength. At Low speeds, the wear rate is sensitive to the sliding speeds and other tribological parameters like applied load and the sliding distance. In the present study, the tribological performance of the polymer-based syntactic foams was reported based on the experiments conducted on a pin-on-disc tribometer. The syntactic foams were manufactured with epoxy as the matrix and the cenospheres obtained from the thermal powerplants as the reinforcement. The experiments were conducted at a sliding speed of the 1 m/s. The applied load was varied from 1 kg to 5 kg up to a sliding distance of 3000 m. The wear rate increased with the sliding distance at lower loads. The trend was reversed at higher loads of 5kg. This may be due to the high plastic deformation at the initial stages when higher loads were applied. This was evident with the higher friction constants for the higher loads. The adhesive wear was found to be predominant for lower loads, while the abrasive wear tracks can be seen in micrographs of samples tested under higher loads.

Keywords: sliding speed, syntactic foams, tribological performance, wear rate

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Authors: Lukas Munster, Pavel Bazant, Ivo Kuritka

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Zinc oxide sub-micro particles and metallic silver nano particles (Ag/ZnO) were deposited on micro crystalline cellulose surface by a fast, simple and environmentally friendly one-pot microwave assisted solvo thermal synthesis in an open vessel system equipped with an external reflux cooler. In order to increase the interaction between the surface of cellulose and the precipitated Ag/ZnO particles, oxidized form of cellulose (cellulose dialdehyde, DAC) prepared by periodate oxidation of micro crystalline cellulose was added to the reaction mixture of Ag/ZnO particle precursors and untreated micro crystalline cellulose. The structure and morphology of prepared hybrid powder materials were analysed by X-ray diffraction (XRD), energy dispersive analysis (EDX), scanning electron microscopy (SEM) and nitrogen absorption method (BET). Microscopic analysis of the prepared materials treated by ultra-sonication showed that Ag/ZnO particles deposited on the cellulose/DAC sample exhibit increased adhesion to the surface of the cellulose substrate which can be explained by the DAC adhesive effect in comparison with the material prepared without DAC addition.

Keywords: microcrystalline cellulose, microwave synthesis, silver nanoparticles, zinc oxide sub-microparticles, cellulose dialdehyde

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Authors: Varsha Baweja

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Steinernema glaseri is known to be the most potent biocontrol agent against a number of insect pests of various orders and of diverse habitats under laboratory conditions. But in nature many micro pathogens may affect the efficacy of such entomopathogenic nematodes. Keeping this in view, the interaction of Steinernema glaseri with a predatory fungus Arthrobotrys superba was assessed on eight different nutrient media. The activity of A.superba was evaluated in terms of trap formation, conidiophore formation, and number of adhesive cells formed in the presence and absence of nematodes. The fungus failed to form any trap on any of the culture media in the absence of nematodes. However, in the presence of nematodes, the trap formation by the test fungus was increased but the number of conidiophores decreased with increase in dilution of Corn Meal Agar from 5% to 2%. Higher number of chlamydospores were observed in phenylalanine treated medium which indicates the inhibiting effect of phenylalanine on the growth of A. superba. Our results suggest that care should be taken during release of entomopathogenic nematodes in an agroecosystem for managing various insect pests in a more efficient manner.

Keywords: Entomopathogenic Nematode , Steinernema Glaseri, Predatory Fungus, Arthrobotrys Superba

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Authors: Sajjad Esmaeili, Robert Krause, Lukas Gerlich, Alireza Mohammadian Kia, Benjamin Uhlig

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This investigation aims to develop the feasible and qualitative process parameters for the thin films fabrication into ultra-large through-silicon-vias (TSVs) as vertical interconnections. The focus of the study is on TSV metallization and its challenges employing new materials for the purpose of rapid signal propagation in the microsystems technology. Cobalt metal-organic chemical vapor deposition (Co-MOCVD) process enables manufacturing an adhesive and excellent conformal ultra-thin film all the way through TSVs in comparison with the conventional non-conformal physical vapor deposition (PVD) process of copper (Cu) seed layer. Therefore, this process provides a Cu seed-free layer which is capable of direct Cu electrochemical deposition (Cu-ECD) on top of it. The main challenge of this metallization module is to achieve the proper alternative seed layer with less roughness, sheet resistance and granular organic contamination (e.g. carbon) which intensify the Co corrosion under the influence of Cu electrolyte.

Keywords: Cobalt MOCVD, direct Cu electrochemical deposition (ECD), metallization technology, through-silicon-via (TSV)

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Authors: Štěpán Hýsek, Milan Podlena, Miloš Pavelek, Matěj Hodoušek, Martin Böhm, Petra Gajdačová

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Particle boards have being used in the civil engineering as a decking for load bearing and non-load bearing vertical walls and horizontal panels (e. g. floors, ceiling, roofs) in a large scale. When the straw is used as non-wood material for manufacturing of lignocellulosic panels, problems with wax layer on the surface of the material can occur. Higher percentage of silica and wax cause the problems with the adhesion of the adhesive and this is the reason why it is necessary to break the surface layer for the better bonding effect. Surface treatment of the particles cause better mechanical properties, physical properties and the overall better results of the composite material are reached. Plasma application is one possibility how to modify the surface layer. The aim of this research is to modify the surface of straw particles by using cold plasma treatment. Surface properties of lignocellulosic materials were observed before and after cold plasma treatment. Cold plasma does not cause any structural changes deeply in the material. There are only changes in surface layers, which are required. Results proved that the plasma application influenced the properties of surface layers and the properties of composite material.

Keywords: composite, lignocellulosic materials, straw, cold plasma, surface treatment

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Authors: S. A. Abdellatef, A. Taniguchi, Namiki, Tsukuba, Ibaraki

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The alterations in the physicochemical characteristics of bio-materials are renowned for their impact in cellular behaviors. Surface chemistry and substratum topography are separately considered as mutable characteristics with deep impact on the overall cell behaviors. In our recent work, we examined the manipulation of the physical cues on hepatic cellular behaviors. We have proven that the geometrical or dimensional characteristics of nano features are essential for the optimum hepatocellular functions. While here, the collective impact of both physical and chemical cues on hepatocellular behaviors was investigated. On which RGD peptide was immobilized on a TiO2 nano pattern that imitates the hierarchically extend collagen nano fibrillar structures. The hepatocytes morphological and functional changes induced by simultaneously combining the diversified cues were investigated. TiO2 substrates that integrate nano topography with the adhesive peptide motif (RGD) had showed an increase in the hepatocellular functionality to the maximum extent. While a significant enhancement in expression of these liver specific markers on RGD coated surfaces were observed compared to uncoated substrates regardless of topography. Consequently in depth understanding of the relationship between various kind of cues and hepatocytes behaviors would be a paving step in the application of tissue engineering and bio reactor technology.

Keywords: biomaterial, tiO2, hepG2, RGD

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Authors: B. Nečasová, P. Liška, J. Šlanhof

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Verification of vented wooden façade system with bonded joints is presented in this paper. The potential of bonded joints is studied and described in more detail. The paper presents the results of an experimental and theoretical research about the effects of freeze cycling on the bonded joint. For the purpose of tests spruce timber profiles were chosen for the load bearing substructure. Planks from wooden plastic composite and Siberian larch are representing facade cladding. Two types of industrial polyurethane adhesives intended for structural bonding were selected. The article is focused on the preparation as well as on the subsequent curing and conditioning of test samples. All test samples were subjected to 15 cycles that represents sudden temperature changes, i.e. immersion in a water bath at (293.15 ± 3) K for 6 hours and subsequent freezing to (253.15 ± 2) K for 18 hours. Furthermore, the retention of bond strength between substructure and cladding was tested and strength in shear was determined under tensile stress. Research data indicate that little, if any, damage to the bond results from freezing cycles. Additionally, the suitability of selected group of adhesives in combination with timber substructure was confirmed.

Keywords: adhesive system, bonded joints, wooden lightweight façade, timber substructure

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Authors: Redha Yeghnem, Laid Boulefrakh, Sid Ahmed Meftah, Abdelouahed Tounsi, El Abbas Adda Bedia

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In this study, the time-dependent behavior of damaged reinforced concrete shear wall structures strengthened with composite plates having variable fibers spacing was investigated to analyze their seismic response. In the analytical formulation, the adherent and the adhesive layers are all modeled as shear walls, using the mixed finite element method (FEM). The anisotropic damage model is adopted to describe the damage extent of the RC shear walls. The phenomenon of creep and shrinkage of concrete has been determined by Eurocode 2. Large earthquakes recorded in Algeria (El-Asnam and Boumerdes) have been tested to demonstrate the accuracy of the proposed method. Numerical results are obtained for non uniform distributions of carbon fibers in epoxy matrices. The effects of damage extent and the delay mechanism creep and shrinkage of concrete are highlighted. Prospects are being studied.

Keywords: RC shear wall structures, composite plates, creep and shrinkage, damaged reinforced concrete structures, finite element method

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Authors: Noushin Shokouhinejad, Hasan Razmi, Reza Fekrazad, Saeed Asgary, Ammar Neshati, Hadi Assadian, Sanam Kheirieh

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This study compared the push-out bond strength of mineral trioxide aggregate (MTA) and a new endodontic cement (NEC) as root-end filling materials in root-end cavities prepared by ultrasonic technique (US) or Er,Cr:YSGG laser (L). Eighty single-rooted extracted human teeth were endodontically treated, apicectomised and randomly divided into four following groups (n = 20): US/MTA, US/NEC, L/MTA and L/NEC. In US/MTA and US/NEC groups, rooted cavities were prepared with ultrasonic retrotip and filled with MTA and NEC, respectively. In L/MTA and L/NEC groups, root-end cavities were prepared using Er, Cr:YSGG laser and filled with MTA and NEC, respectively. Each root was cut apically to create a 2 mm-thick root slice for measurement of bond strength using a universal testing machine. Then, all slices were examined to determine the mode of bond failure. Data were analysed using two-way ANOVA. Root-end filling materials showed significantly higher bond strength in root-end cavities prepared using the ultrasonic technique (US/MTA and US/NEC) (P < 0.001). The bond strengths of MTA and NEC did not differ significantly. The failure modes were mainly adhesive for MTA, but cohesive for NEC. In conclusion, bond strengths of MTA and NEC to root-end cavities were comparable and higher in ultrasonically prepared cavities.

Keywords: bond strength, Er, Cr:YSGG laser, MTA, NEC, root-end cavity

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Authors: Maizatulnisa Othman, Mohamad Bukhari, Zahurin Halim, Souad A. Muhammad, Khalisani Khalid

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Sandwich structure composites produced by epoxy core and aluminium skin were developed as potential building materials. Interface bonding between core and skin was controlled by varying kenaf content. Five different weight percentage of kenaf loading ranging from 10 wt% to 50 wt% were employed in the core manufacturing in order to study the mechanical properties of the sandwich composite. Properties of skin aluminium with epoxy were found to be affected by drying time of the adhesive. Mechanical behavior of manufactured sandwich composites in relation with properties of constituent materials was studied. It was found that 30 wt% of kenaf loading contributed to increase the flexural strength and flexural modulus up to 102 MPa and 32 Gpa, respectively. Analysis were done on the flatwise and edgewise compression test. For flatwise test, it was found that 30 wt% of fiber loading could withstand maximum force until 250 kN, with compressive strength results at 96.94 MPa. However, at edgewise compression test, the sandwich composite with same fiber loading only can withstand 31 kN of the maximum load with 62 MPa of compressive strength results.

Keywords: sandwich structure composite, epoxy, aluminium, kenaf fiber

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Authors: Hamza Javar Magnier, Leslie V. Woodcock

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It has been reported that at temperatures above the critical there is no “continuity of liquid and gas”, as originally hypothesized by van der Waals. Rather, both gas and liquid phases, with characteristic properties as such, extend to supercritical temperatures. Each phase is bounded by the locus of a percolation transition, i.e. a higher-order thermodynamic phase change associated with percolation of gas clusters in a large void, or liquid interstitial vacancies in a large cluster. Between these two-phase bounds, it is reported there exists a mesophase that resembles an otherwise homogeneous dispersion of gas micro-bubbles in liquid (foam) and a dispersion of liquid micro-droplets in gas (mist). Such a colloidal-like state of a pure one-component fluid represents a hitherto unchartered equilibrium state of matter besides pure solid, liquid or gas. Here we provide compelling evidence, from molecular dynamics (MD) simulations, for the existence of this supercritical mesophase and its colloidal nature. We report preliminary results of computer simulations for a model fluid using a simplistic representation of atoms or molecules, i.e. a hard-core repulsion with an attraction so short that the atoms are referred to as “adhesive spheres”. Molecular clusters, and hence percolation transitions, are unambiguously defined. Graphics of color-coded clusters show colloidal characteristics of the supercritical mesophase.

Keywords: critical phenomena, mesophase, supercritical, square-well, critical parameters

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Authors: Ulli Heinlein, Thomas Freimann

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Pre-applied bonded membranes are used as positive-side waterproofing on concrete basements, are installed before the concrete work, and achieve a tear-resistant and waterproof bond with the subsequently placed fresh concrete. This bond increases redundancy compared to lose waterproofing membranes by preventing lateral water migrations in the event of damage. So far, the membranes have been tested in the laboratory, but it is not yet known how they behave on construction sites in the presence of dirt, soil, cement paste or moisture. This article, therefore, conducts investigations on six construction sites using 18 test slabs where the pre-applied bonded membranes are selectively contaminated or wetted. Subsequently, cores are taken, and the influence of the contaminations on the adhesive tensile strength and waterproof bond is tested. Pre-applied bonded membranes with smooth or granular but closed surfaces show no sensitivity to wetness, whereas open-pored membranes with nonwovens do not tolerate standing water. Contaminations decline the performance of all pre-applied bonded membranes since a separating layer is formed between the bonding layer and the concrete. The influence depends on the thickness of the contamination and its mechanical properties.

Keywords: waterproofing, positive-side waterproofing, basement, pre-applied bonded waterproofing membrane, In-situ testing, lateral water migrations

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Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

Abstract:

Zirconium alloys exhibit low neutron absorption cross-section and excellent mechanical properties. Due to these unique characteristics, these materials are widely used in designing core components of pressurized heavy water reactors (PHWRs). Another material that is widely used in the design of reactor core is stainless steel. Under operating conditions of the reactor, there are possibilities for mechanical and tribological interaction between the components made of zirconium alloy (Zr-2.5 Nb) and stainless steel (SS-410). This may result in wear of the material. To study the tribological characteristics of Zr-2.5 Nb and SS-410, low amplitude reciprocating wear tests are conducted at room temperature and at high temperatures (260 degrees Celsius). The tests are conducted at frequencies ranging from 5 Hz to 25 Hz. The displacement amplitude is varied from 200 µm to 600 µm. The responses are recorded, analyzed and correlated with damage observed using scanning electron microscopy (SEM) and an optical profilometer. Energy dispersive spectroscopy (EDS) is used to study the damage mechanism prevailing at the contact interface. A higher coefficient of friction (COF) is observed at higher temperatures as compared to the one at room temperature. Tests carried out at high temperature reveals adhesive wear as the dominant mechanism resulting in significant material transfer.

Keywords: PHWRs, Zr-2.5Nb, SS-410, wear

Procedia PDF Downloads 55

Authors: Olena Grygorieva

Abstract:

Nowadays mechanisms of thymocytes emigration from the thymus to the periphery are investigated actively. We have proposed a hypothesis of thymocytes’ migration from the thymus through lymphatic vessels during periodical short-term local edema. By morphological, hystochemical methods we have examined quantity of lymphocytes, epitelioreticulocytes, mast cells, blood and lymphatic vessels in morpho-functional areas of rats’ thymuses during the first week after birth in 4 hours interval. In newborn and beginning from 8 hour after birth every 12 hours specific density of the thymus, absolute quantity of microcirculatory vessels, especially of lymphatic ones, lymphcyte-epithelial index, quantity of mast cells and their degranulative forms increase. Structure of extracellular matrix, intrathymical microenvironment and lymphocytes’ adhesive properties change. Absolute quantity of small lymphocytes in thymic cortex changes wavy. All these changes are straightly expressed from 0 till 2, from 12 till 16, from 108 till 120 hours of postnatal life. During this periods paravasal lymphatic vessels are stuffed with lymphocytes, i.e. discrete migration of lymphocytes from the thymus occurs. After rapid edema reduction, quantity of lymphatic vessels decrease, they become empty. Therefore, in the thymus of newborn periodical short-term local edema is observed, on its top discrete migration of lymphocytes from the thymus occurs.

Keywords: lymphocytes, lymphatic vessels, mast cells, thymus

Procedia PDF Downloads 196

Authors: Qian Qiao, Tongjin Xiao, Hongtu He, Jiaxin Yu

Abstract:

This study is focused on the synergetic effects of water and sulfur dioxide treatments (SO₂ treatments) on the mechanochemical wear of SLS glass. It is found that the wear behavior of SLS glass in humid air is very sensitive to the water and SO₂ treatment environments based on the wear test using a ball-on-flat reciprocation tribometer. When SLS glass is treated with SO₂-without, the presence of water, the wear resistance of SLS glass in humid air becomes significantly higher compared to the pristine glass. However, when SLS glass is treated with SO₂ with the presence of water, the wear resistance of SLS glass decreases remarkably with increasing in the relative humidity (RH) from 0% to 90%. Further analyses indicate that when sodium ions are leached out of SLS glass surface via the water and SO₂ treatments, the mechanochemical properties of SLS glass surface become different depending on the RH. At lower humidity, the nano hardness of the Na⁺-leached surface is higher, and it can contribute to the enhanced wear resistance of SLS glass. In contrast, at higher humidity conditions, the SLS glass surface is more hydrophilic, and substantial wear debris can be found inside the wear track of SLS glass. Those phenomena suggest that adhesive wear and abrasive wear dominate the wear mechanism of SLS glass in humid air, causing the decreased wear resistance of SLS glass with increasing the RH. These results may not only provide a deep understanding of the wear mechanism of SLS glass but also helpful for operation process of functional and engineering glasses.

Keywords: soda lime silicate glass, wear, water, SO₂

Procedia PDF Downloads 139