Search results for: reinforced

Authors: A. Mir, C. Aribi, B. Bezzazi

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Work presented is interested in the characterization of the quasistatic mechanical properties and in fatigue of a composite laminated in jute/epoxy. The natural fibers offer promising prospects thanks to their interesting specific properties, because of their low density, but also with their bio deterioration. Several scientific studies highlighted the good mechanical resistance of the vegetable fiber composites reinforced, even after several recycling. Because of the environmental standards which become increasingly severe, one attends the emergence of eco-materials at the base of natural fibers such as flax, bamboo, hemp, sisal, jute. The fatigue tests on elementary vegetable fibers show an increase of about 60% of the rigidity of elementary fibers of hemp subjected to cyclic loading. In this study, the test-tubes manufactured by the method infusion have sequences of stacking of 0/90° and ± 45° for the shearing and tensile tests. The quasistatic tests reveal a variability of the mechanical properties of about 8%. The tensile fatigue tests were carried out for levels of constraints equivalent to half of the ultimate values of the composite. Once the fatigue tests carried out for well-defined values of cycles, a series of static tests of traction type highlights the influence of the number of cycles on the quasi static mechanical behavior of the laminate jute/epoxy.

Keywords: jute, epoxy resin, mechanical, static, dynamic behavior

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Authors: Yannick Willemin

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Carbon fibre-reinforced plastic (CFRP) offers outstanding value. However, like all materials, CFRP also has its challenges. Many forming processes are largely manual and hard to automate, making it challenging to control repeatability and reproducibility (R&R); they generate significant scrap and are too slow for high-series production; fibre costs are relatively high and subject to supply and cost fluctuations; the supply chain is fragmented; many forms of CFRP are not recyclable, and many materials have yet to be fully characterized for accurate simulation; shelf life and outlife limitations add cost; continuous-fibre forms have design limitations; many materials are brittle; and small and/or thick parts are costly to produce and difficult to automate. A majority of small structural parts are metal due to high CFRP fabrication costs for the small-size class. The fact that CFRP manufacturing processes that produce the highest performance parts also tend to be the slowest and least automated is another reason CFRP parts are generally higher in cost than comparably performing metal parts, which are easier to produce. Fortunately, business is in the midst of a major manufacturing evolution—Industry 4.0— one technology seeing rapid growth is additive manufacturing/3D printing, thanks to new processes and materials, plus an ability to harness Industry 4.0 tools. No longer limited to just prototype parts, metal-additive technologies are used to produce tooling and mold components for high-volume manufacturing, and polymer-additive technologies can incorporate fibres to produce true composites and be used to produce end-use parts with high aesthetics, unmatched complexity, mass customization opportunities, and high mechanical performance. A new hybrid manufacturing process combines the best capabilities of additive—high complexity, low energy usage and waste, 100% traceability, faster to market—and post-consolidation—tight tolerances, high R&R, established materials, and supply chains—technologies. The platform was developed by Zürich-based 9T Labs AG and is called Additive Fusion Technology (AFT). It consists of a design software offering the possibility to determine optimal fibre layup, then exports files back to check predicted performance—plus two pieces of equipment: a 3d-printer—which lays up (near)-net-shape preforms using neat thermoplastic filaments and slit, roll-formed unidirectional carbon fibre-reinforced thermoplastic tapes—and a post-consolidation module—which consolidates then shapes preforms into final parts using a compact compression press fitted with a heating unit and matched metal molds. Matrices—currently including PEKK, PEEK, PA12, and PPS, although nearly any high-quality commercial thermoplastic tapes and filaments can be used—are matched between filaments and tapes to assure excellent bonding. Since thermoplastics are used exclusively, larger assemblies can be produced by bonding or welding together smaller components, and end-of-life parts can be recycled. By combining compression molding with 3D printing, higher part quality with very-low voids and excellent surface finish on A and B sides can be produced. Tight tolerances (min. section thickness=1.5mm, min. section height=0.6mm, min. fibre radius=1.5mm) with high R&R can be cost-competitively held in production volumes of 100 to 10,000 parts/year on a single set of machines.

Keywords: additive manufacturing, composites, thermoplastic, hybrid manufacturing

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Authors: Yadgar Tayfur, Antony Darby, Tim Ibell, Mark Evernden, John Orr

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Fabric form-work is a technique to cast concrete structures with a great advantage of saving concrete material of up to 40%. This technique is particularly associated with the optimized concrete structures that usually have smaller cross-section dimensions than equivalent prismatic members. However, this can make the structural system produced from these members prone to smaller serviceability safety margins. Therefore, it is very important to understand the serviceability issue of non-prismatic concrete structures. In this paper, an analytical computer-based model to optimize concrete beams and to predict load-deflection behaviour of both prismatic and non-prismatic concrete beams is presented. The model was developed based on the method of sectional analysis and integration of curvatures. Results from the analytical model were compared to load-deflection behaviour of a number of beams with different geometric and material properties from other researchers. The results of the comparison show that the analytical program can accurately predict the load-deflection response of concrete beams with medium reinforcement ratios. However, it over-estimates deflection values for lightly reinforced specimens. Finally, the analytical program acceptably predicted load-deflection behaviour of on-prismatic concrete beams.

Keywords: fabric-formed concrete, continuous beams, optimisation, serviceability

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Authors: Violeta Damjanovic-Behrendt

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This paper presents an approach for optimal cyber security decisions to protect instances of a federated Internet of Things (IoT) platform in the cloud. The presented solution implements the repeated Stackelberg Security Game (SSG) and a model called Stochastic Human behaviour model with AttRactiveness and Probability weighting (SHARP). SHARP employs the Subjective Utility Quantal Response (SUQR) for formulating a subjective utility function, which is based on the evaluations of alternative solutions during decision-making. We augment the repeated SSG (including SHARP and SUQR) with a reinforced learning algorithm called Naïve Q-Learning. Naïve Q-Learning belongs to the category of active and model-free Machine Learning (ML) techniques in which the agent (either the defender or the attacker) attempts to find an optimal security solution. In this way, we combine GT and ML algorithms for discovering optimal cyber security policies. The proposed security optimization components will be validated in a collaborative cloud platform that is based on the Industrial Internet Reference Architecture (IIRA) and its recently published security model.

Keywords: security, internet of things, cloud computing, stackelberg game, machine learning, naive q-learning

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Authors: Ehsan Sadie

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The use of steel braces in concrete structures has been considered by researchers in recent decades due to its easy implementation, economics and the ability to create skylights in braced openings compared to shear wall openings as well as strengthening weak concrete structures to earthquakes. The purpose of this article is to improve and strengthen concrete structures with steel bracing. In addition, cases such as different numbers of steel braces in different openings of concrete structures and interaction between concrete frames and metal braces have been studied. In this paper, by performing static nonlinear analysis and examining ductility, the relative displacement of floors, examining the performance of samples, and determining the coefficient of behavior of composite frames (concrete frames with metal bracing), the behavior of reinforced concrete frames is compared with frame without bracing. The results of analyzes and studies show that the addition of metal bracing increases the strength and stiffness of the frame and reduces the ductility and lateral displacement of the structure. In general, the behavior of the structure against earthquakes will be improved.

Keywords: behavior coefficient, bracing, concrete structure, convergent bracing, earthquake, linear static analysis, nonlinear analysis, pushover curve

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Authors: Hani Mekdash, Lina Jaber, Yehia Temsah

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Underground space is becoming a necessity nowadays, especially in highly congested urban areas. Retaining underground excavations using shoring systems is essential in order to protect adjoining structures from potential damage or collapse. Reinforced Concrete Piles (RCP) supported by multiple rows of tie-back anchors are commonly used type of shoring systems in deep excavations. However, executing anchors can sometimes be challenging because they might illegally trespass neighboring properties or get obstructed by infrastructure and other underground facilities. A technique is proposed in this paper, and it involves the addition of eccentric high-strength steel strands to the RCP section through ducts without providing the pile with lateral supports. The strands are then vertically stressed externally on the pile cap using a hydraulic jack, creating a compressive strengthening force in the concrete section. An experimental study about the behavior of the shoring wall by pre-stressed piles is presented during the execution of an open excavation in an urban area (Beirut city) followed by numerical analysis using finite element software. Based on the experimental results, this technique is proven to be cost-effective and provides flexible and sustainable construction of shoring works.

Keywords: deep excavation, prestressing, pre-stressed piles, shoring system

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Authors: Minjung Kim, Hyunkoo Kang, Jinkoo Kim

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In this study, a seismic retrofit scheme for a reinforced concrete shear wall structure using steel slit dampers was presented. The stiffness and the strength of the slit damper used in the retrofit were verified by cyclic loading test. A genetic algorithm was applied to find out the optimum location of the slit dampers. The effects of the slit dampers on the seismic retrofit of the model were compared with those of jacketing shear walls. The seismic performance of the model structure with optimally positioned slit dampers was evaluated by nonlinear static and dynamic analyses. Based on the analysis results, the simple procedure for determining required damping ratio using capacity spectrum method along with the damper distribution pattern proportional to the inter-story drifts was validated. The analysis results showed that the seismic retrofit of the model structure using the slit dampers was more economical than the jacketing of the shear walls and that the capacity spectrum method combined with the simple damper distribution pattern led to satisfactory damper distribution pattern compatible with the solution obtained from the genetic algorithm.

Keywords: seismic retrofit, slit dampers, genetic algorithm, jacketing, capacity spectrum method

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Authors: Azza Taha Zaki

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The position Eugene O’Neill occupies in the history of American drama is undisputable. Critics have agreed that the American theatre was waiting for O’Neill to give it substance, character, and value. The American dramatist continues to be considered as a major influence on the body of dramatic repertoire across the globe. The American theatre before O’Neill knew playwrights who were mostly viewed as entertainers. The serious drama had to wait until O’Neill started his career with expressionistic and social drama. His breakthrough, however, came in 1925 when he published Desire Under the Elms, described as the first important tragedy to be written in America. Mourning Becomes Electra, published in 1931, further reinforced the reputation of Eugene O’Neill and was described as his 'magnum opus'. Aspiring to portray the essence of life and man’s innermost conflicts, O’Neill turned to the classical model, rather than to social realistic drama, to create modern tragedies with the aid of the then-new science of psychology. The present paper aims to undertake an in-depth study of how overtones from classical tragedies by the classical masters Aeschylus, Sophocles, and Euripides resonate through O’Neill’s two plays. The paper shows how leaning on classical themes and concepts interpreted in terms of psychological forces have added depth and tragic substance to a modern milieu and produced masterpieces of dramaturgy.

Keywords: classical, drama, O'Neill, modern, tragic

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Authors: Michael Sigruener, Dirk Muscat, Nicole Struebbe

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Fiber reinforcement is a state of the art to enhance mechanical properties in plastics. For concrete and civil engineering, steel reinforcements are commonly used. Steel reinforcements show disadvantages in their chemical resistance and weight, whereas polymer fibers' major problems are in fiber-matrix adhesion and mechanical properties. In spite of these facts, longevity and easy handling, as well as chemical resistance motivate researches to develop a polymeric material for fiber reinforced concrete. Adhesion and interfacial mechanism in fiber-polymer-composites are already studied thoroughly. For polymer fibers used as concrete reinforcement, the bonding behavior still requires a deeper investigation. Therefore, several differing polymers (e.g., polypropylene (PP), polyamide 6 (PA6) and polyetheretherketone (PEEK)) were spun into fibers via single screw extrusion and monoaxial stretching. Fibers then were embedded in a concrete matrix, and Single-Fiber-Pull-Out-Tests (SFPT) were conducted to investigate bonding characteristics and microstructural interface of the composite. Differences in maximum pull-out-force, displacement and slope of the linear part of force vs displacement-function, which depicts the adhesion strength and the ductility of the interfacial bond were studied. In SFPT fiber, debonding is an inhomogeneous process, where the combination of interfacial bonding and friction mechanisms add up to a resulting value. Therefore, correlations between polymeric properties and pull-out-mechanisms have to be emphasized. To investigate these correlations, all fibers were introduced to a series of analysis such as differential scanning calorimetry (DSC), contact angle measurement, surface roughness and hardness analysis, tensile testing and scanning electron microscope (SEM). Of each polymer, smooth and abraded fibers were tested, first to simulate the abrasion and damage caused by a concrete mixing process and secondly to estimate the influence of mechanical anchoring of rough surfaces. In general, abraded fibers showed a significant increase in maximum pull-out-force due to better mechanical anchoring. Friction processes therefore play a major role to increase the maximum pull-out-force. The polymer hardness affects the tribological behavior and polymers with high hardness lead to lower surface roughness verified by SEM and surface roughness measurements. This concludes into a decreased maximum pull-out-force for hard polymers. High surface energy polymers show better interfacial bonding strength in general, which coincides with the conducted SFPT investigation. Polymers such as PEEK or PA6 show higher bonding strength in smooth and roughened fibers, revealed through high pull-out-force and concrete particles bonded on the fiber surface pictured via SEM analysis. The surface energy divides into dispersive and polar part, at which the slope is correlating with the polar part. Only polar polymers increase their SFPT-function slope due to better wetting abilities when showing a higher bonding area through rough surfaces. Hence, the maximum force and the bonding strength of an embedded fiber is a function of polarity, hardness, and consequently surface roughness. Other properties such as crystallinity or tensile strength do not affect bonding behavior. Through the conducted analysis, it is now feasible to understand and resolve different effects in pull-out-behavior step-by-step based on the polymer properties itself. This investigation developed a roadmap on how to engineer high adhering polymeric materials for fiber reinforcement of concrete.

Keywords: fiber-matrix interface, polymeric fibers, fiber reinforced concrete, single fiber pull-out test

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Authors: Abdelmalk Brahma

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Drying is a phenomenon that accompanies the hardening of hydraulic materials. It can, if it is not prevented, lead to significant spontaneous dimensional variations, which the cracking is one of events. In this context, cracking promotes the transport of aggressive agents in the material, which can affect the durability of concrete structures. Drying shrinkage develops over a long period almost 30 years although most occurred during the first three years. Drying shrinkage stabilizes when the material is water balance with the external environment. The drying shrinkage of cementitious materials is due to the formation of capillary tensions in the pores of the material, which has the consequences of bringing the solid walls of each other. Knowledge of the shrinkage characteristics of concrete is a necessary starting point in the design of structures for crack control. Such knowledge will enable the designer to estimate the probable shrinkage movement in reinforced or prestressed concrete and the appropriate steps can be taken in design to accommodate this movement. This study is concerned the modelling of drying shrinkage of the hydraulic materials and the prediction of the rate of spontaneous deformations of hydraulic materials during hardening. The model developed takes in consideration the main factors affecting drying shrinkage. There was agreement between drying shrinkage predicted by the developed model and experimental results. In last we show that developed model describe the evolution of the drying shrinkage of high performances concretes correctly.

Keywords: drying, hydraulic concretes, shrinkage, modeling, prediction

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Authors: Ali Raza, Rūta Rimašauskienė

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In the current work, the fused deposition modelling (FDM) technique is used to manufacture PLA reinforced with carbon fibre composite structures with two unique layer patterns, 0°\0° and 0°\90°. The purpose of the study is to investigate the dynamic characteristics of each fabricated composite structure. The Macro Fiber Composite (MFC) is embedded with 0°/0° and 0°/90° structures to investigate the effect of an MFC (M8507-P2 type) patch on vibration amplitude suppression under dynamic loading circumstances. First, modal analysis testing was performed using a Polytec 3D laser vibrometer to identify bending mode shapes, natural frequencies, and vibration amplitudes at the corresponding natural frequencies. To determine the stiffness of each structure, several loads were applied at the free end of the structure, and the deformation was recorded using a laser displacement sensor. The findings confirm that a structure with 0°\0° layers pattern was found to have more stiffness compared to a 0°\90° structure. The maximum amplitude suppression in each structure was measured using a laser displacement sensor at the first resonant frequency when the control voltage signal with optimal phase was applied to the MFC. The results confirm that the 0°/0° pattern's structure exhibits a higher displacement reduction than the 0°/90° pattern. Moreover, stiffer structures have been found to perform amplitude suppression more effectively.

Keywords: carbon fibre composite, MFC, modal analysis stiffness, stiffness

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Authors: Ambuj Srivastava, Narender Singh

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This paper presents the effect of installation of cylindrical external store on the performance, stability, control and handling qualities of light transport category aircraft. A pair of long cylindrical store was installed symmetrically on either side of the fuselage (port and starboard) ahead of the wing and below the fuselage bottom surface running below pilot and co-pilot window. The cylindrical store was installed as hanging from aircraft surface through specially designed brackets. The adjoining structure was sufficiently reinforced for bearing aerodynamic loads. The length to diameter ratio of long cylindrical store was ~20. Based on academic studies and flow simulation analysis, a considerable detrimental effect on single engine second segment climb performance was found which was later validated through extensive flight testing exercise. The methodology of progressive flight envelope opening was adopted. The certification was sought from Regional airworthiness authorities and for according approval.

Keywords: second segment climb, maximum operating speed, cruise performance (single engine and twin engine), minimum control speed, and additional trim required

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Authors: M. S. Belashov, A. V. Benin, Lin Hong, Sh. Sh. Nazarova, O. B. Sabirova, A. M. Uzdin, Lin Hong

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The features of calculating structures for the action of weak earthquakes are analyzed. Earthquakes with a recurrence of 30 years and 50 years are considered. In the first case, the structure is to operate normally without damage after the earthquake. In the second case, damages are allowed that do not affect the possibility of the structure operation. Three issues are emphasized: setting elastic and damping characteristics of reinforced concrete, formalization of limit states, and combinations of loads. The dependence of damping on the reinforcement coefficient is estimated. When evaluating limit states, in addition to calculations for crack resistance and strength, a human factor, i.e., the possibility of panic among people, was considered. To avoid it, it is proposed to limit a floor-by-floor speed level in certain octave ranges. Proposals have been developed for estimating the coefficients of the combination of various loads with the seismic one. As an example, coefficients of combinations of seismic and ice loads are estimated. It is shown that for strong actions, the combination coefficients for different regions turn out to be close, while for weak actions, they may differ.

Keywords: weak earthquake, frequent earthquake, damage, limit state, reinforcement, crack resistance, strength resistance, a floor-by-floor velocity, combination coefficients

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Authors: Yunus Dere

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Minarets are tower like structures where the call to prayer of Muslims is performed. They have a symbolic meaning and sacred place among Muslims. Being tall and slender, they are prone to damage under earthquakes and strong winds. Kursuncular stone minaret was built around thirty years ago in Konya/TURKEY. Its core and helical stairs are made of reinforced concrete. Its stone spire was damaged during a light earthquake. Its spire is later replaced with a light material covered with lead sheets. In this study, the natural frequencies and mode shapes of Kursuncular minaret is obtained experimentally and analytically. First an ambient vibration test is carried out using a data acquisition system with accelerometers located at four locations along the height of the minaret. The collected vibration data is evaluated by operational modal analysis techniques. For the analytical part of the study, the dimensions of the minaret are accurately measured and a detailed 3D solid finite element model of the minaret is generated. The moduli of elasticity of the stone and concrete are approximated using the compressive strengths obtained by Windsor Pin tests. Finite element modal analysis of the minaret is carried out to get the modal parameters. Experimental and analytical results are then compared and found in good agreement.

Keywords: experimental modal analysis, stone minaret, finite element modal analysis, minarets

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Authors: Faci Youcef

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In the present work, an experimental study is carried out using the digital image correlation (DIC) technique to analyze the damage and behavior of woven composite carbon/epoxy under tensile loading. The tension mechanisms associated with failure modes of bolted joints in advanced composites are studied, as well as displacement distribution and strain distribution. The evolution value of bolt angle inclination during tensile tests was studied. In order to compare the distribution of displacements and strains along the surface, figures of image mapping are made. Several factors that are responsible for the failure of fiber-reinforced polymer composite materials are observed. It was found that strain concentrations observed in the specimens can be used to identify full-field damage onset and to monitor damage progression during loading. Moreover, there is an interaction between laminate pattern, laminate thickness, fastener size and type, surface strain concentrations, and out-of-plane displacement. Conclusions include a failure analysis associated with bolt angle inclinations and supported by microscopic visualizations of the composite specimen. The DIC results can be used to develop and accurately validate numerical models.

Keywords: Carbone, woven, damage, digital image, bolted joint, the inclination of angle

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Authors: Naser Alenezi, Ibrahim Alsakkaf, Osama Eid

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The main objective of this study is to develop an independent reliability based code for reinforced concrete (R/C) structural components and elements solely for the State of Kuwait and its neighboring countries. The proposed code will take into account the harsh Kuwait’s harsh environment, loading conditions and material strengths. The method for developing such a code is based on structural reliability theory that takes into accounts the specific geographical and the various prescribed societal environment of the Kuwait region. These methods were developed according to the following four components: (1) loads, (2) structural strength, (3) reliability analysis, and (4) achieving target reliability levels (reliability index ’s ). The final product from this study will be a design code for R/C structural elements that include beams and columns, and some other structural members. This reliability-based LRFD design code will provide appropriate, easy, fast, and economical approach for designing R/C structural elements such as, beams and columns, for both houses and bridges, and other concrete structures. In addition, this reliability-based codified design of R/C beams, columns, and, possibly, concrete slabs will improve the design and serviceability of R/C bridge and building systems in Kuwait and neighboring GCC countries. Also, it has the potential to reduce the cost of new concrete structures, as fewer materials are used with more design efficiency.

Keywords: live laod, design, evaluation, structural building

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Authors: Zohaib Ellahi, Guolong Zhao

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Ceramic matrix composite (CMC) material possesses high strength, wear resistance and anisotropy thus machining of this material is very difficult and demands high cost. In this research, FEM simulations and physical experiments have been carried out to assess the machinability of carbon fiber reinforced silicon carbide (C/SiC) using polycrystalline diamond (PCD) tool in slot milling process. Finite element model has been generated in Abaqus/CAE software and milling operation performed by using user defined material subroutine. Effect of different milling parameters on cutting forces and stresses has been calculated through FEM simulations and compared with experimental results to validate the finite element model. Cutting forces in x and y-direction were calculated through both experiments and finite element model and found a good agreement between them. With increase in cutting speed resultant cutting forces are decreased. Resultant cutting forces are increased with increased feed per tooth and depth of cut. When machining performed along the fiber direction stresses generated near the tool edge were minimum and increases with fiber cutting angle.

Keywords: experimental & numerical investigation, C/SiC cutting performance analysis, milling of CMCs, CMC composite stress analysis

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Authors: Ederaldo Godoy Junior, Ricardo O. Jesus, Pedro H. Jesus, José R. Camargo, Jorge Y. Oliveira, Nicoly Milhardo Lourenço

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This work aimed at the comparative study of the quality and quantity of biogas produced by archaea strain Methanothrix soehngenii operating in different versions of anaerobic digesters upflow sludge bed in the brewery wastewater treatment in Brazil in the tropical region. Four types of UASB digesters were studied made of different geometries and materials which are: a UASB IC steel 20 meters high; a circular UASB steel 6 meters high; an UASB reinforced concrete lined with geomembrane PEAB with 6 meters high; and finally a UASB plug flow comprising two UASB in serious rotomolded HDPE 6 meters high.Observed clearly that the biogas produced in the digester UASB steel H2S concentrations had values lower than the HDPE. With respect to efficiency in short time, the UASB IC showed the best results to absorb overloads, as the UASB circular steel showed an efficiency of 90% removal of the organic load. The UASB system plug flow in HDPE showed the lowest cost of deployment, and its efficiency in removing the organic load was 80%.

Keywords: biogas, achaeas, UASB, Brewery effluent

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Authors: Bachir Kacimi, Fatiha Teklal, Arezki Djebbar

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Forming processes induce residual deformations on the reinforcement and sometimes lead to mesoscopic defects, which are more recurrent than macroscopic defects during the manufacture of complex structural parts. This study deals with the influence of the fabric shear and buckles defects, which appear during draping processes of composite, on the impact behavior of a glass fiber reinforced polymer. To achieve this aim, we produced several specimens with different amplitude of deformations (shear) and defects on the fabric using a specific bench. The specimens were manufactured using the contact molding and tested with several impact energies. The results and measurements made on tested specimens were compared to those of the healthy material. The results showed that the buckle defects have a negative effect on elastic parameters and revealed a larger damage with significant out-of-plane mode relatively to the healthy composite material. This effect is the consequence of a local fiber impoverishment and a disorganization of the fibrous network, with a reorientation of the fibers following the out-of-plane buckling of the yarns, in the area where the defects are located. For the material with calibrated shear of the reinforcement, the increased local fiber rate due to the shear deformations and the contribution to stiffness of the transverse yarns led to an increase in mechanical properties.

Keywords: Defects, Forming, Impact, Induced properties, Textiles

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Authors: Sumaira Mukhtar

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The present research aims at the discussion of the subversion of the hegemony of the feminine self in the text Moth Smoke by a Pakistani novelist Mohsin Hamid. It presents the notion of the subversion of the grand narratives of the ‘positioning’ of feminine identity in Pakistani patriarchal society by presenting a de-stereotyped personality of Mumtaz, the protagonist in Moth Smoke. The dominant masculine traits in Mumtaz’s personality have been negotiated since she is an untraditional female character in the novel. In this regard, the researcher has taken a feministic stance in this study by presenting the proposition that subaltern can also speak. Mumtaz’s character reminds one of Hedda from Henrik Ibsen’s play Hedda Gabler. So, the masculine traits in Mumtaz’s personality have also been compared with Hedda’s. Besides, the research study will also bring into notice that how that in the postmodern scenario, marginalization of the women have been responded back by women and hereby Mumtaz by uplifting her social status and class. Her de-stereotyped feminine self has been reinforced by the dialogues and incidents in the text. This research is qualitative in design and is based on the textual analysis. An interpretive research method has also been utilized since the researcher has tried to decode the text in supporting the notion of de-stereotyping of feminine self. This research would add to the body of Pakistani literature and Feministic theory.

Keywords: de-stereotyped, feminine identity, marginalization, masculine traits

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Authors: F. Sangiorgio, J. Silfwerbrand, G. Mancini

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Geometric and mechanical properties all influence the resistance of RC structures and may, in certain combination of property values, increase the risk of a brittle failure of the whole system. This paper presents a statistical and probabilistic investigation on the resistance of RC beams designed according to Eurocodes 2 and 8, and subjected to multiple failure modes, under both the natural variation of material properties and the uncertainty associated with cross-section and transverse reinforcement geometry. A full probabilistic model based on JCSS Probabilistic Model Code is derived. Different beams are studied through material nonlinear analysis via Monte Carlo simulations. The resistance model is consistent with Eurocode 2. Both a multivariate statistical evaluation and the data clustering analysis of outcomes are then performed. Results show that the ultimate load behaviour of RC beams subjected to flexural and shear failure modes seems to be mainly influenced by the combination of the mechanical properties of both longitudinal reinforcement and stirrups, and the tensile strength of concrete, of which the latter appears to affect the overall response of the system in a nonlinear way. The model uncertainty of the resistance model used in the analysis plays undoubtedly an important role in interpreting results.

Keywords: modelling, Monte Carlo simulations, probabilistic models, data clustering, reinforced concrete members, structural design

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Authors: Olha Yarova

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This study is a collaborative project between the American University of Central Asia and parent association of children with Down syndrome ‘Sunterra’ that took place in Bishkek, Kyrgyzstan. The purpose of the study was to explore whether principles and techniques of applied behavior analysis (ABA) could be used to teach children with Down syndrome socially significant behaviors. ABA is considered to be one of the most effective treatment for children with autism, but little research is done on the particularity of using ABA to children with Down syndrome. The data for the study was received during clinical observations; work with children with Down syndrome and interviews with their mothers. The results show that many ABA principles make the work with children with Down syndrome more effective. Although such children very rarely demonstrate aggressive behavior, they show a lot of escape-driven and attention seeking behaviors that are reinforced by their parents and educators. Thus functional assessment can be done to assess the function of problem behavior and to determine appropriate treatment. Prompting and prompting fading should be used to develop receptive and expressive language skills, and enhance motor development. Even though many children with Down syndrome work for praise, it is still relevant to use tangible reinforcement and to know how to remove them. Based on the results of the study, the training for parents of children with Down syndrome will be developed in Kyrgyzstan, country, where children with Down syndrome are not accepted to regular kindergartens and where doctors in maternity hospitals tell parents that their child will never talk, walk and recognize them

Keywords: down syndrome, applied behavior analysis, functional assessment, problem behavior, reinforcement

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Authors: M. Fette, J. P. Wulfsberg, A. Herrmann, R. H. Ladstaetter

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Present and future lightweight design represents an important key to successful implementation of energy-saving, fuel-efficient and environmentally friendly means of transport in the aerospace and automotive industry. In this context the use of carbon fibre reinforced plastics (CFRP) which are distinguished by their outstanding mechanical properties at relatively low weight, promise significant improvements. Due to the reduction of the total mass, with the resulting lowered fuel or energy consumption and CO2 emissions during the operational phase, commercial aircraft and future vehicles will increasingly be made of CFRP. An auspicious technology for the efficient and economic production of high performance thermoset composites and hybrid structures for future lightweight applications is the combination of carbon fibre sheet moulding compound (SMC), tailored continuous carbon fibre reinforcements and metallic components in a one-shot pressing and curing process. This paper deals with a new hybrid composite technology for aerospace industries, which was developed with the help of a universal innovation and development system. This system supports the management of idea generation, the methodical development of innovative technologies and the achievement of the industrial readiness of these technologies.

Keywords: development system, hybrid composite, innovation system, prepreg, sheet moulding compound

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Authors: Amine Rezzoug, Said Abdi, Nadjet Bouhelal, Ismail Daoud

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This paper investigates the application of metallic coatings on high fiber volume fraction carbon/epoxy polymer matrix composites. For the grip of the metallic layer, a method of modifying the surface of the composite by introducing a mixture of copper and steel powder (filler powders) which can reduce the impact of thermal spray particles. The powder was introduced to the surface at the time of the forming. Arc spray was used to project the zinc coating layer. The substrate was grit blasted to avoid poor adherence. The porosity, microstructure, and morphology of layers are characterized by optical microscopy, SEM and image analysis. The samples were studied also in terms of hardness and erosion resistance. This investigation did not reveal any visible evidence damage to the substrates. The hardness of zinc layer was about 25.94 MPa and the porosity was around (∼6.70%). The erosion test showed that the zinc coating improves the resistance to erosion. Based on the results obtained, we can conclude that thermal spraying allows the production of protective coating on PMC. Zinc coating has been identified as a compatible material with the substrate. The filler powders layer protects the substrate from the impact of hot particles and allows avoiding the rupture of brittle carbon fibers.

Keywords: arc spray, coating, composite, erosion

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Authors: Suresh Vidyasagar Chevuri, D. B. Karunakar Chevuri

Abstract:

The main advantages of 'Metal Matrix Nano Composites (MMNCs)' include excellent mechanical performance, good wear resistance, low creep rate, etc. The method of fabrication of MMNCs is quite a challenge, which includes processing techniques like Spark Plasma Sintering (SPS), etc. The objective of the present work is to fabricate aluminum based MMNCs with the addition of small amounts of yttrium using Spark Plasma Sintering and to evaluate their mechanical and microstructure properties. Samples of 2024 AA with yttrium ranging from 0.1% to 0.5 wt% keeping 1 wt% TiB2 constant are fabricated by Spark Plasma Sintering (SPS). The mechanical property like hardness is determined using Vickers hardness testing machine. The metallurgical characterization of the samples is evaluated by Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FE-SEM) and X-Ray Diffraction (XRD). Unreinforced 2024 AA sample is also fabricated as a benchmark to compare its properties with that of the composite developed. It is found that the yttrium addition increases the above-mentioned properties to some extent and then decreases gradually when yttrium wt% increases beyond a point between 0.3 and 0.4 wt%. High density is achieved in the samples fabricated by spark plasma sintering when compared to any other fabrication route, and uniform distribution of yttrium is observed.

Keywords: spark plasma sintering, 2024 AA, yttrium addition, microstructure characterization, mechanical properties

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Authors: Muhammad Tariq A. Chaudhary

Abstract:

Soil-structure interaction (SSI) in bridges under seismic excitation is a complex phenomenon which involves coupling between the non-linear behavior of bridge pier columns and SSI in the soil-foundation part. It is a common practice in the study of SSI to model the bridge piers as linear elastic while treating the soil and foundation with a non-linear or an equivalent linear modeling approach. Consequently, the contribution of soil and foundation to the SSI phenomenon is disproportionately highlighted. The present study considered non-linear behavior of bridge piers in FEM model of a 4-span, pile-supported bridge that was designed for five different soil conditions in a moderate seismic zone. The FEM model of the bridge system was subjected to a suite of 21 actual ground motions representative of three levels of earthquake hazard (i.e. Design Basis Earthquake, Functional Evaluation Earthquake and Maximum Considered Earthquake). Results of the FEM analysis were used to delineate the influence of pier column non-linearity and SSI on critical design parameters of the bridge system. It was found that pier column non-linearity influenced the bridge lateral displacement and base shear more than SSI for majority of the analysis cases for the class of bridge investigated in the study.

Keywords: bridge, FEM model, reinforced concrete pier, pile foundation, seismic loading, soil-structure interaction

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Authors: Abdul Qader Melhem, Hacene Badache

Abstract:

This paper deals with the theoretical and experimental study of shear connection via simple steel reinforcement shear connectors, which are steel reinforcing bars bent into L-shapes, instead of commonly used headed studs. This suggested L-shape connectors are readily available construction material in steel reinforcement. The composite section, therefore, consists of steel inverted T-section being embedded within a lightly reinforced concrete flange at the top slab as a unit. It should be noted that the cross section of these composite models involves steel inverted T-beam, replacing the steel top flange of a standard commonly employed I-beam section. The paper concentrates on the elastic and elastic-plastic behavior of these composite models. Failure modes either by cracking of concrete or shear connection be investigated in details. Elastic and elastoplastic formulas of the composite model have been computed for different locations of NA. Deflection formula has been derived, its value was close to the test value. With a supportive designing curve, this curve is valuable for both designing engineers and researchers. Finally, suggested designing curves and valuable equations will be presented. A check is made between theoretical and experimental outcomes.

Keywords: composite, elastic-plastic, failure, inverted T-section, L-Shape connectors

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Authors: Min Yu, Olivier T. Picot, Theo Graves Saunders, Ivo Dlouhy, Amit Mahajan, Michael J. Reece

Abstract:

Graphene was successfully introduced into a polymer-derived silicon oxycarbide (SiOC) matrix by phase transfer of graphene oxide (GO) from an aqueous (GO dispersed in water) to an organic phase (copolymer as SiOC precursor in diethyl ether). With GO concentrations increasing up to 2 vol%, graphene-containing flakes self-assembled into a lamellar structure in the matrix leading to composite with the anisotropic property. Spark plasma sintering (SPS) was applied to densify the composites with four different GO concentrations (0, 0.5, 1 and 2 vol%) up to ~2.3 g/cm3. The fracture toughness of SiOC-2 vol% GO composites was significantly increased by ~91% (from 0.70 to 1.34 MPa·m¹/²), at the expense of a decrease in the flexural strength (from 85MPa to 55MPa), compared to SiOC-0 vol% GO composites. Moreover, the electrical conductivity in the perpendicular direction (σ┴=3×10⁻¹ S/cm) in SiOC-2 vol% GO composite was two orders of magnitude higher than the parallel direction (σ║=4.7×10⁻³ S/cm) owing to the self-assembled lamellar structure of graphene in the SiOC matrix. The composites exhibited increased electrical conductivity (σ┴) from 8.4×10⁻³ to 3×10⁻¹ S/cm, with the increasing GO content from 0.5 to 2 vol%. The SiOC-2 vol% GO composites further showed the better electrochemical performance of oxygen reduction reaction (ORR) than pure graphene, exhibiting a similar onset potential (~0.75V vs. RHE) and more positive half-wave potential (~0.6V vs. RHE).

Keywords: composite, fracture toughness, flexural strength, electrical conductivity, electrochemical performance

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Authors: Masood Ahmed

Abstract:

There is a plethora of literature (including judicial and extra-judicial comments) concerning the virtues of alternative dispute resolution processes within the English civil justice system. Lord Woolf in his Access to Justice Report ushered in a new pro-ADR philosophy and this was reinforced by Sir Rupert Jackson in his review of civil litigation costs. More recently, Briggs LJ, in his review of the Chancery Court, reiterated the significant role played by ADR and the need for better integration of ADR processes within the Chancery Court. His Lordship also noted that ADR which had failed to produce a settlement (i.e. a failed-ADR) continued to play a significant role in contributing to a ‘substantial narrowing of the issues or increased focus on the key issues’ which were ‘capable of assisting both the parties and the court in the economical determination of the dispute at trial.’ With the assistance of empirical data, this paper investigates the nature of failed-ADR and, in particular, assesses the effectiveness of failed-ADR processes as a tool in: (a) narrowing the legal and/or factual issues which may assist the courts in more effective and efficient case management of the dispute; (b) assisting the parties in the future settlement of the matter. This paper will also measure the effectiveness of failed-ADR by considering the views and experiences of legal practitioners who have engaged in failed-ADR.

Keywords: English civil justice system, alternative dispute resolution processes, civil court process, empirical data from legal profession regarding failed ADR

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Authors: Jain Jyoti, Jain Shorab, Sinha Shishir

Abstract:

In the current scenario, development of new biodegradable composites with the reinforcement of some plant derived natural fibers are in major research concern. Abundant quantity of these natural plant derived fibers including sisal, ramp, jute, wheat straw, pine, pineapple, bagasse, etc. can be used exclusively or in combination with other natural or synthetic fibers to augment their specific properties like chemical, mechanical or thermal properties. Among all natural fibers, wheat straw, bagasse, kenaf, pineapple leaf, banana, coir, ramie, flax, etc. pineapple leaf fibers have very good mechanical properties. Being hydrophilic in nature, pineapple leaf fibers have very less affinity towards all types of polymer matrixes. Not much work has been carried out in this area. Surface treatments like alkaline treatment in different concentrations were conducted to improve its compatibility towards hydrophobic polymer matrix. Pineapple leaf fiber epoxy composites have been prepared using hand layup method. Effect of variation in fiber loading up to 20% in epoxy composites has been studied for mechanical properties like tensile strength and flexural strength. Analysis of fiber morphology has also been studied using FTIR, XRD. SEM micrographs have also been studied for fracture surface.

Keywords: composite, mechanical, natural fiber, pineapple leaf fiber

Procedia PDF Downloads 239