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Masonry structures are economical, easy to construct and has important advantages such as the use of natural materials. In Turkey, these structures have been heavily built especially with traditional construction methods and nowadays they are popular as well. Therefore, the reinforcement of masonry structures and seismic safety are of paramount importance. Masonry walls are not naturally stable and cannot be considered as homogeneous structures so it is difficult to predict their behavior under load by using numerical methods. Supportive framework of the mathematical model and the data of the experimental studies are required. In this study, 36 wall blocks were prepared in 900 × 900 × 200 mm using hollow masonry brick, blend brick and aerated concrete and these blocks are reinforced with Carbon Fiber Reinforced Polymer in both directions by using three different methods. For the analysis of retrofit brick walls produced and reinforced with different materials, ASTM E591 test method was used. At the end of the experiment period; shear strength performances of the reinforcement methods of the elements, their deformation and energy dissipation capacities were evaluated. According to results, maximum shear strength performance was observed at the masonry panel strengthened by two face. Maximum load value was 172.63 Kn. Also maximum dissipation capacity was observed at the masonry wall reinforced with CFRP covered diagonally. Maximum energy dissipation capacity was 317.1 J. © 2018 Elsevier Ltd

Materials play a fundamental role in defining the vibrational and acoustic characteristics of structures and their importance is even increasing because of the continuing demand for lightweight products. Carbon Fibre Reinforced Plastics (CRFP) components are becoming more and more popular because of their excellent mechanical properties but are unfortunately almost unable to dissipate energy. This is one of the reasons why their usage is limited to structural components and does not directly affect acoustic and vibrational response, which are among the factors responsible for harshness and comfort. In vehicles, for example, large panels of CFRP are as noisy as metallic panels so that this kind of lightweight structures is only used when a limited mass is of paramount importance, e.g. in racing cars. The chance of incorporating a damping material in the stacking sequence of CF layers that define a composite seems to be a viable solution to ameliorate the vibrational behaviour of composite materials. This configuration permits to cure the damping layers together with the resins, in order to obtain both free and constrained layer solutions. In this paper, the Oberst beam method has been chosen to determine the elastic modulus and loss factor of such materials, as a function of both frequency and temperature. Three nominally identical samples for each configuration have been tested in a temperature controlled environment, according to the Oberst beam test method. The effects of aging have been simulated by an accelerated standard procedure, with cyclically varying temperature and humidity for a total of 792 h (3 cycles x 264 h). The analysis of experimental data has been performed in the frequency domain by a least square fitting procedure, aimed at outperforming the simple half-power point method. An open source version of the fitting technique has also been implemented and can be obtained from the authors under the CC-by license.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2017-02-23, 資料番号: PA1710071000

In practical application, carbon fiber reinforced plastics (CFRP) structures are easy to appear all sorts of invisible damages. So the damages should be timely located and detected for the safety of CFPR structures. In this paper, an acoustic emission (AE) localization system based on fiber Bragg grating (FBG) sensing network and support vector regression (SVR) is proposed for damage localization. AE signals, which are caused by damage, are acquired by high speed FBG interrogation. According to the Shannon wavelet transform, time differences between AE signals are extracted for localization algorithm based on SVR. According to the SVR model, the coordinate of AE source can be accurately predicted without wave velocity. The FBG system and localization algorithm are verified on a 500 mm×500 mm×2 mm CFRP plate. The experimental results show that the average error of localization system is 2.8 mm and the training time is 0.07 s.

The influence of porosity on the ultrasonic wave propagation in unidirectional carbon-fiber-reinforced composite laminates is investigated based on the two-dimensional finite element analysis and measurements. Random distributions of pores with different contents and size are considered in the analysis, together with the effects of viscoelastic plies and interlaminar resin-rich regions. The transient reflection waveforms are calculated from the frequency-domain finite-element solutions by the inverse Fourier transform. As the measures for porosity characterization, the ultrasonic wave velocity, attenuation coefficient, and interlaminar interface echo characteristics are examined for 24-ply unidirectional composite laminates. As a result, the wave velocity decreases with the porosity content in a manner insensitive to the pore size. On the other hand, the attenuation coefficient increases both with the porosity content and with the pore size. The time–frequency analysis of the reflection waveforms shows that the temporal decay rate of interlaminar interface echoes at the stop-band frequency is a good indicator of the porosity content. The measured porosity-content dependence of the wave velocity is better reproduced by the numerical simulations when the interlayer interfacial stiffnesses are adjusted according to the porosity content, indicating that not only the porosity features but also the interlaminar interfacial properties vary with curing conditions.

Linear robots, numerically controlled machines and articulated robots are some of the major components in automation. In various applications, these single systems are linked together to become advanced mechatronic systems since they can realize special and general tasks. Unfortunately, the degree of automation in carbon fiber reinforced plastic (CFRP) manufacturing is currently rather low. A lot of research still needs to be done in order to achieve the knowledge necessary to gain a consistent, robust and reliable production chain for CFRP. The most decisive criterion in automation is the tradeoff between speed in production and the attainable layup accuracy. One aspect that affects accuracy is vibration caused by rapid movement and interaction forces. In the case of advanced mechatronic systems, the effect of the dynamic coupling is one key factor in accuracy. Over the last few decades, the field of active vibration suppression has made use of its excellent capability to improve the accuracy of machines. Therefore, the paper presents a comprehensive review of active vibration suppression technology for the improvement of precision in manufacturing. The work is mainly focused on, but not limited to, the production of components made of CFRP. The paper concludes with a discussion of promising approaches to identify a trend for future work.

Fiber reinforced polymers (FRPs) show advantageous physical-mechanical, thermal, and dielectric characteristics, making them promising candidates for weight reduction in structural applications. However, machinability is often difficult because of the specificity of their structure. This paper highlights the latest advances in CFRP drilling. Key papers are analyzed with respect to workpiece materials, geometrical tool features, and input variables (such as variation in process parameters). The influence of tool geometry and process parameters on workpiece delamination and hole quality/integrity represents the primary focus of this review. In addition, some new data are presented and discussed.

The use of carbon fiber reinforced plastic (CFRP) has contributed in producing light-weighted and strong aircraft structures. However, the low impact resistance of CFRP makes it easier for internal damages to occur. By using thin-ply prepeg with thickness of less than 0.05 mm, laminates with smaller differences in fiber orientation angle and with the same thickness as the conventional laminates can be formed. This study investigates and compares the mechanical properties and damage behaviours between quasi-isotropic laminates with fiber orientation angle mismatch of 45 degrees (45QI) and laminates with small fiber orientation angle mismatch of 15 degrees (15QI). Both laminates are loaded in tension in 0, 7.5, 15 and 22.5 degrees. Low velocity impact tests are also conducted. From tensile testing, 15QI laminates shows more isotropic properties in strength than 45QI. Damages were observed by using microscopic and X-ray images. Crack propagation in width direction can be prevented in 15QI laminates. From low velocity impact testing, we understand that impact responses are not depending so much on the fiber orientation angle mismatch. In terms of internal damage, 15QI laminates has smaller delaminated area near the impact point compared to 45QI laminates.

For the development of a robot based laser cutting process of automotive 3D parts consisting of carbon fibre reinforced plastics (CFRP), investigations with a newly developed fibre guided nanosecond pulsed laser with an average power of P L = 1.5 kW were conducted. In order to investigate the best combination of quality and process time 2 different optical fibres were used, with diameters of d f = 400 μm and d f = 600 μm. The main differences between the two setups are the resulting focal diameter and the maximum available pulse energy up to E P = 80 mJ. In a first instance, a comparable investigation was performed with both fibres for a constant pulse overlap. For each fibre the minimum required line energy was investigated and cuts were performed, distributed over the complete parameter range of the laser source. The influences of the fibre diameter on the quality and efficiency of the cutting process are summarized and discussed.

Potentials of integrating new technologies, particularly carbon fiber reinforced plastics, are not fully considered conventional reengineering processes. This paper firstly addresses the benefit by integration of functions, reduction of weight and fuel consumption, substitution of rare materials and customer individuality. Consequently, these aspects have been evaluated in three case studies, comprising representative cultural goods (eg. pipe organs), components of sport-aircraft (eg. ultralight helicopters) and urban-transport (eg. multifunctional stroller-bicycle trailer). Therefore, the following methods have been applied: functional analysis, reverse engineering and measuring technologies.

The production rates of carbon fiber reinforced plastic (CFRP) parts are rising constantly which in turn drives research to bring a higher level of automation to the manufacturing processes of CFRP. Resin transfer molding (RTM), which is seen as a production method for high volumes, has been accelerated to a high degree. However, complex net-shape preforms are necessary for this process, which are widely manually manufactured. To face these challenges a new concept for the manufacturing of carbon fiber preforms with a form-flexible gripping, draping and joining end-effector is presented and discussed. Furthermore, this paper investigates the application of this concept, describes the initial build-up of a demonstrator, focusing on material selection and heating technology, and discusses test results with the prototype. This prototype already validates the feasibility of the proposed concept on the basis of a generic preform geometry. After a summary, this paper discusses future in-depth research concerning the concept and its application in more complex geometries.

With the intention to develop a robot based laser cutting process for automotive 3D parts with varying thickness consisting of carbon fibre reinforced plastics (CFRP), strategies of 2D investigations were adapted. The used setup consist of a fibre guided nanosecond pulsed laser with an average power of PL = 1.5 kW, a 6-axis robot and a 3D programmable focusing optic (I-PFO). In a first instance strategies for the remote cutting of material with a thickness of d = 5 mm were developed and optimized concerning cutting efficiency and quality. In a second step the results were transferred to a robot based 3D cutting process. Main challenges are the consideration of the correct angle of incidence, the geometric constancy and the accessibility of the cutting geometry by the I-PFO for complex shaped 3D parts. Therewith, “cutting-on-the-fly” strategies were realized for automated trimming and drilling of large automotive structures.

The accuracy of reliability analysis of structures made up of CFRP composites rely on the quantification of the uncertainties associated with composite material properties. This study focuses on the experimental characterisation of random field models for the material uncertainties. As a first step, a number of experimental tests on identical samples have been conducted as per ASTM standards. Assuming second order random fields to be appropriate for modelling the uncertain variations along the spatial extent in the macro-scale, statistical tests have been carried out to examine the suitability of some commonly used models for the probability density function for the various mechanical properties of the material. The spatial correlations observed from experimental tests have been compared with some of the commonly used correlation functions and suitable empirical models have been proposed. Finally, the importance of appropriate modelling of the parameters has been highlighted through a numerical example. � 2014 Elsevier Ltd.

Carbon fiber reinforced plastics (CFRP) show high potential for use in lightweight applications not only in aircraft design, but also in the automotive or wind energy industry. However, processing of CFRP is complex and expensive due to their outstanding mechanical properties. One possibility to manufacture CFRP structures flexibly at acceptable process speeds is high-power laser cutting. Though showing various advantages such as contactless energy transfer, this process is connected to potentially hazardous emission of respirable dust and organic gases. Moreover, the emitted particles may be fibrous, thus requiring particular attention. Here, a systematic analysis of the hazardous substances emitted during laser cutting of CFRP with thermoplastic and thermosetting matrix is presented. The objective is to evaluate emission rates for the total particulate and gaseous fractions as well as for different organic key components. Furthermore, the influence of the laser process conditions shall be assessed, and first proposals to handle the emissions adequately are made.

The present work intends to provide a numerical tool for the efficient design of the multidirectional carbon fiber reinforced plastic (CFRP) material using finite element simulation software ABAQUS ® . A 3D model has been established for simulation of the tensile test composite specimen which enables to understand the mechanical strength and strain at failure of the composite materials. 15 ply CFRP specimens with various stacking sequences were analyzed for their strength and displacement. Exhaustive parametric studies reveal the dependency of reinforcing material and ply orientation on the strength and stiffness of composite materials. Carbon fibers with cross ply lamination were found to be stiffer than angle ply glass fiber lamination. A fairly good comparison was obtained between the predicted results with available experimental and theoretical data in open literature

A hybrid structural health monitoring (SHM) system, consisting of a piezoelectric transducer and fiber optic sensors (FOS) for generating and monitoring Lamb waves, was investigated to determine their potential for damage detection and localization in composite aerospace structures. As part of this study, the proposed hybrid SHM system, together with an in-house developed algorithm, was evaluated to detect and localize two types of damage: a through thickness damage (hole of 2 mm in diameter) and a surface damage (2 mm diameter bore hole with a depth of 0.65 mm) located on the backside of the plate. The experiments were performed using an aircraft representative composite plate skin, manufactured from carbon fiber reinforced polymer (CFRP).

This paper presents the results of 15 experimental tests on rectangular slender reinforced concrete (RC) beams. The results reveal limitations in existing theoretical formulations to estimate the failure moment capacity and mode of failure. An improved theoretical formulation is proposed here to predict the critical buckling moment including effects related to nonlinearity and cracking of concrete. Also, following the trends in steel design, an improved measure of slenderness ratio is proposed. Based on a study of 72 test results, it is shown that there is an interaction between flexural tension and instability modes of failure in moderately slender beams. To avoid lateral instability failure, it is suggested that the slenderness ratio be limited to unity. A 'moment reduction factor' is also proposed to account for slenderness effects in RC beams. � 2011 Elsevier Ltd.

The steel caging technique is used to strengthen RC columns all over the world, as it has been shown to be effective, economical and easy to apply. Most studies carried out to date on this strengthening technique have focussed on isolated sections of columns subjected to axial loads. This paper deals with an experimental study on the behaviour of RC columns strengthened by steel caging under combined bending and axial loads. Full-size specimens were laboratory tested and the beam-column joint was also simulated. Two different types of element were used to solve the strengthening in the zone nearest to the joint. These were: (1) capitals welded to the steel cage in contact with the beam and (2) steel tubes joining the cage on both sides of the joint. The results obtained show that the technique described considerably increases the resistance and ductility of columns strengthened in this way. The results are compared with those that could be obtained with the proposal of Eurocode No. 4 and also with the results of two other similar studies. © 2010 Elsevier Ltd. All rights reserved., The authors wish to express their gratitude for the financial support received from the Spanish Ministry of Science and Technology under Research Project MAT 2003-08075. Also to the Generalitat Valenciana for its financial support within the GVPRE/2008/153 Project. Mr. Garzon-Roca is grateful to the Generalitat Valenciana for the scholarship awarded to him to complete his doctorate studies. Thanks are also due to Ester Gimenez, Salvador Ivorra, and Francisco J. Pallares for their invaluable assistance from the beginning of the Project.

Masonry is one of the conventional materials that is being used throughout the world due to its accessibility, functionality and cost but they fail in earthquakes mainly due to their low tensile and shear resistance. The objective of this investigation is to study the effectiveness of GFRP composite retrofitting on the behaviour of masonry wallettes and shear triplets that are cast with low stiffness table moulded bricks and high stiffness cement mortar through experimental and finite element study. Experiments were conducted on masonry wallettes under compression in different orientations and triplets under shear. Finite element models for the analysis of wallettes and shear triplets is developed using the FE software ABAQUS and validated with the experimental data. The concepts of macromodeling with smeared crack concrete model for masonry wallettes and micromodeling with the elastic properties of brick and mortar for shear triplets are used for the analysis. The changes in deformational capacity and ultimate load resistance are calculated for varying thickness and fiber orientations of GFRP composites. Based on this study, it is concluded that the strength and axial stiffness of the wallettes under compression and strength of shear triplets is increased due to external bonding of GFRP composites. The comparison of finite element and experimental results proved that macromodeling can be used to study behaviour of masonry wallettes retrofitted with GFRP composites and micromodeling is feasible for the analysis of small scale specimens such as triplets. � 2007 Elsevier Ltd. All rights reserved.

Force is considered to be one of the indicators that best describe the machining process. Measured force can be used to evaluate the quality and geometric profile of the machined part. In this paper, a combinatorial optimization approach is used to characterize the effect of force on the quality of a machined part made of Carbon Fiber Reinforced Polymers (CFRP) material. The approach is called Logical Analysis of Data (LAD) and is based on machine learning and pattern recognition. LAD is used in order to map the machining conditions, in terms of force and torque that lead to conforming products and those which lead to nonconforming products. In this paper, the LAD technique is applied to the drilling of CFRP plates, and the results, based on data obtained experimentally, are reported. A discussion of the potential use of LAD in manufacturing concludes the paper., 5th International Conference on Industrial Engineering and Operations Management, IEOM 2015, 3 March 2015 through 5 March 2015

Carbon fiber-reinforced polymer structures are being increasingly used in aerospace applications. In this work, analytical, numerical, and experimental investigations are carried out to understand the structural response of debonded carbon fiber-reinforced polymer splice joint subjected to compression load. It is found that debonds are of major importance for the behavior of carbon fiber-reinforced polymer splice-joint structures. A series of carbon fiber-reinforced polymer splice-joint specimens are subjected to compressive loading by introducing an artificial debond at one of the interfaces in the splice joint and compared with specimens without debond. Although the compressive behavior is similar to that of nominal splice joint, the stiffness is considerably decreased in the presence of debond, and also the load-carrying capacity is reduced by 17% approximately. The experimental results are compared with the analytical predictions and numerical simulations using (a) the Rayleigh-Ritz method and (b) the finite element method, respectively, and are in good correlation. � The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Carbon fiber reinforced polymer (CFRP) is an important composite material. It has many applications in aerospace and automotive fields. The little information available about the machining process of this material, specifically when routing process is considered, makes the process control quite difficult. In this paper, we propose a new process control technique and we apply it to the routing process for that important material. The measured machining conditions are used to evaluate the quality and the geometric profile of the machined part. The machining conditions, whether controllable or uncontrollable are used to control part accuracy and its quality. We present a pattern-based machine learning approach in order to detect the characteristic patterns, and use them to control the quality of a machined part at specific range. The approach is called logical analysis of data (LAD). LAD finds the characteristic patterns which lead to conforming products and those that lead to nonconforming products. As an example, LAD is used for online control of a simulated routing process of CFRP. We introduce the LAD technique, we apply it to the high speed routing of woven carbon fiber reinforced epoxy, and we compare the accuracy of LAD to that of an artificial neural network, since the latter is the most known machine learning technique. By using experimental results, we show how LAD is used to control the routing process by tuning autonomously the routing conditions. We conclude with a discussion of the potential use of LAD in manufacturing.

A finite element study is carried out for assessing the elastic displacement response of a typical CFRP payload fairing due to separation impulse. Different stacking sequences for the CFRP laminates are considered and their influence on the displacement response studied. Lanczos method is used for eigenvalue analysis and mode superposition method for the response study. The effect of the elastic response on the radial gap is also studied.A finite element study is carried out for assessing the elastic displacement response of a typical CFRP payload fairing due to separation impulse. Different stacking sequences for the CFRP laminates are considered and their influence on the displacement response studied. Lanczos method is used for eigenvalue analysis and mode superposition method for the response study. The effect of the elastic response on the radial gap is also studied.

Cyclostationarity is an inherent characteristic of many communication signals, which can be exploited for performing various signal processing tasks. Determining the cyclic statistics of a signal of interest is often necessary in the design of signal processing systems exploiting this cyclostationary behaviour. This work investigates the second order cyclic statistics of various signalling schemes employed in ultra wideband impulse radio systems. Analytical expressions are derived for the cyclic autocorrelation and spectral correlation density functions. Publisher's Version Q2 WOS:000260000200004

For the spent upper-stage rocket and defunct spacecraft bodies reentering the Earth's atmosphere, the extent of aerothermal degradation depends on the rate of energy dissipated during flight and on the thermal characteristics of the material. It is well known that the reentry trajectory and the aerodynamic heating are significantly influenced by the aerodynamic drag. In this paper, a study involving the measurement of rarefied drag and of material degradation under simulated reentry heating is reported. The rarefied drag coefficient was experimentally determined by direct pressure measurements in a rarefied wind tunnel. From the ensuing reentry trajectory, the aerodynamic heating was estimated. The material thermal response and the physical nature of degradation were studied experimentally through transient heat flux simulations. Results of the experiments are compared with numerical results of transient heat flux simulations. Various space faring materials were considered for study and the sensitivity of the thickness on degradation was brought out. It was found that aluminum alloys and carbon fiber reinforced plastics have the potential for early degradation, whereas columbium and similar high-temperature alloys would possibly survive the reentry heating environments. � 2012 AIAA.

Cataloged from PDF version of article. Carbon fiber reinforced polymers (CFRP) have emerged as the material of choice to satisfy increasing demand for lighter aircrafts. Machinability characteristics of CFRPs are quite different than those of metals; therefore, special tool designs have been developed for CFRP machining. The double helix end mill design compresses the upper and lower sides of the laminate using opposite helix angles that eliminate delamination. A mechanistic force model for double helix tools is developed based on milling force data obtained on flat end mills. The proposed model can be used to improve double helix tool designs and to optimize milling process parameters. 2013 CIRP.

Cataloged from PDF version of article. Carbon fiber reinforced plastics (CFRPs) have many desirable properties, including high strength-toweight ratio, high stiffness-to-weight ratio, high corrosion resistance, and low thermal expansion. These properties make CFRP suitable for use in structural components for aerospace applications. Drilling is the most common machining process applied to CFRP laminates, and it is difficult due to the extremely abrasive nature of the carbon fibers and low thermal conductivity of CFRP. It is a challenge for manufacturers to drill CFRP materials without causing any delamination on the work part while also considering the economics of the process. The subject of this study is the drilling of fabric woven type CFRP laminates which are known to be more resistant to delamination than unidirectional type CFRP laminates. The objective of this study is to investigate the influence of double point angle drill geometry on drilling performance through an experimental approach. An uncoated carbide and two diamond coated carbide drills with different drill tip angles are employed in drilling experiments of aerospace quality thick fabric woven CFRP laminates. Force and torque measurements are used to investigate appropriate drilling conditions based on drill geometry and ideal drilling parameters are determined. Tool life tests of the drills were conducted and the condition of the diamond coating is examined as a function of drilling operational parameters. High feed rate drilling experiments are observed to be favorable in terms of drill wear. Feed is observed to be more important than speed, and the upper limit of feed is dictated by the drill design and the rigidity of the machine drill. Hole diameter variation due to drill wear is monitored to determine drill life. At high feeds, hole diameter tolerance is observed to be more critical than hole exit delamination during drilling of fabric woven CFRP laminates. © 2012 Elsevier B.V. All rights reserved.

The results of a study of the magnetic, NGR and other parameters of EuO:Fe composites, which really meet the requirements imposed on the use of them as spin injectors in the developed semiconductor spin-electronic structures capable of operating under normal conditions at room temperatures, are reported. The manifestation of superparamagnetism in these composites is established. Copyright © 2008 American Scientific Publishers. All rights reserved.

Lamb-wave tomography (LWT) offers a powerful nondestructive technique for the health assessment of large structures as their propagation properties depend on the thickness and the mechanical properties of the material. Development of a fast and accurate algorithm for defect detection is of paramount importance in any structural-health-monitoring (SHM) system. The present study explores the prospects of LWT as a SHM technique with an accent on developing a suitable algorithm for real-time inspection. Projection data is collected by electronically scanning an array of ultrasonic sensors arranged in a modified cross-hole geometry. The data thus collected is investigated to extract energy profile of the traveling waves. Multiplicative algebraic reconstruction technique (MART) algorithms are used as a tool for tomographic reconstruction from a set of multiple independent measurements. The performance of algorithms is evaluated from the point of view of the cost of algorithm, achievable resolution, and accuracy of results. Experimental results show that MART is capable of characterizing defects in thin isotropic and composite plates within a reasonable error band (�26% normalized, �2.6 RMS) and is suitable for application to LWT of large structures such as aircraft skins.

Stitching is used to reduce dry-core (incomplete infusion of T-joint core) and reinforce T-joint structure. However, it may cause new types of flaws, especially submillimeter flaws. Microscopic inspection, ultrasonic c-scan, pulsed thermography, vibrothermography, and laser spot thermography are used to investigate the internal flaws in a stitched T-joint carbon fiber-reinforced polymer (CFRP) matrix composites. Then, a new microlaser line thermography is proposed. Microcomputed tomography (microCT) is used to validate the infrared results. A comparison between microlaser line thermography and microCT is performed. It was concluded that microlaser line thermography can detect the internal submillimeter defects. However, the depth and size of the defects can affect the detection results. The microporosities with a diameter of less than 54 mu m are not detected in the microlaser line thermography results. Microlaser line thermography can detect the microporosity (a diameter of 0.162 mm) from a depth of 90 mu m. However, it cannot detect the internal microporosity (a diameter of 0.216 mm) from a depth of 0.18 mm. The potential causes are given. Finally, a comparative study is conducted.

Near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminate strips are used to increase the load-carrying capacity of concrete structures by inserting them into slits made in the concrete cover of the elements to be strengthened and gluing them to the concrete with an epoxy adhesive. In several cases the NSM technique has substantial advantages when compared with externally bonded laminates. In order to assess the bond behavior between the CFRP and concrete under monotonic and cyclic loading, an experimental program, based on a series of pullout bending tests, was carried out. The influence of the bond length and loading history on the bond behavior was investigated. In this work the details of the tests are described, and the obtained results are discussed. Using the experimental data and an analytical-numerical strategy, a local bond stress-slip relationship was determined. A finite element analysis was performed to evaluate the influence of the adhesive on the global response observed in the pullout bending tests., The first author wishes to acknowledge the grant SFRH/BD/3259/2000 provided by FCT (Portuguese Foundation for Science and Technology) and FSE (European Social Fund). The tests were performed at the Structural Technology Laboratory of the Technical University of Catalonia, Spain, with the help of Miguel Angel Martín and Ernesto Diaz. The authors wish to acknowledge the support provided by S&P and Bettor MBT who supplied the material used in the study.

A new design methodology is developed to mold the polymer spur gears with high strength fiber reinforcement only in the highly stressed region. High performance high cost short carbon fiber reinforced Nylon 66 is used in the highly stressed tooth region and low cost unreinforced Nylon 66 is used in the hub region. Two different geometries, circular and spline shaped hubs were used for developing the selective reinforced gears by multi-shot injection-molding process. Joint strength of the selectively reinforced gear was estimated using shear tests. Clear hub and tooth region separation without any distortion was observed in joint shear tests. A molten material due to fusion bonding was observed at the interfaces. The joint strength was also evaluated by conducting gear fatigue tests using a power absorption test rig at various torque levels and at a constant gear rotational speed. Monolithic reinforced gear and selective reinforced gears with spline hub exhibited similar fatigue behavior. The failure mode depends upon the test torque level. The selective reinforced gears with circular hub showed joint failures at high-test torque levels. Absence of mechanical interlocking feature in the circular hub geometry contributes to the joint failure. Thermal bond, part interference and mechanical interlocking feature provide sufficient joint strength to the selective reinforced gear with spline hub. � Springer 2006.

This paper deals with the formulation of a nine-noded piezolaminated degenerated shell finite element for modeling and analysis of multilayer composite general shell structures with bonded/embedded distributed piezoelectric sensors and actuators. The distributed PZT sensors and actuators used in the composite smart structures are relatively thin and could have arbitrary variation of curvatures and thicknesses. They cannot be modeled with shell elements based on curvilinear shell theories which would need the specification of constant shell curvatures and thicknesses. Modeling them with piezo finite elements available in popular commercial codes like ABAQUS, ANSYS, MARC, etc, would need relatively greater computational effort as they are based on solid element formulation. In view of these, the present proposed degenerated piezoelectric shell element would be a better choice giving good computational accuracy and efficiency. The main advantage of a degenerate shell element is that it is not based on any shell theories and is applicable over a wide range of curvatures and thicknesses. This element is developed by using the degenerate solid approach based on Reissner-Mindlin assumptions which allow the shear deformation and rotary inertia effect to be considered and the 3D field is reduced to a 2D field in terms of mid-surface nodal variables. Uniformly reduced integration is carried out to overcome membrane locking and shear locking and the numerical integration is carried out in all three directions to obtain accurate results. The present element has 45 elastic degrees of freedom and 10 electric degrees of freedom per piezoelectric layer in the element. The potential induced due to bending deformation is more accurately represented by assuming quadratic variation of the electric potential through the thickness of each piezoelectric layer. This is achieved by interpolating using nodal mid-plane electric potentials and one electric degree of freedom representing the potential difference between the top and bottom surfaces of the piezoelectric layer. Few case studies of composite general shells with piezoelectric sensors and actuators have been considered by modeling them with the above elements and the active vibration control performance has been studied using linear quadratic Gaussian (LQG) control. � 2008 IOP Publishing Ltd.

Within the aircraft industry, the use of composite materials such as carbon fiber reinforced plastics (CFRPs) is steadily increasing, especially in structural parts. Manufacturability needs to be considered in aircraft design to ensure a cost-effective manufacturing process. The aim of this paper is to describe the development of a new strategy for how SAAB Aerostructures addressing manufacturability issues during the development of airframe composite structures. Through literature review, benchmarking and company interviews, a design for manufacturing (DFM) strategy was developed. The strategy ensures that the important factors for successful DFM management are implemented on strategic, tactical and operational levels that contribute to a more cost-efficient product development process and aircraft design.

Pin-connected precast concrete structures are widely used in some European countries of moderate seismicity. However, this structural system is not earthquake resistant because it does not have enough lateral stiffness or lateral-load resistance. Lack of a rigid diaphragm at the roof level imposes severe forces to connections., It is difficult to strengthen such buildings with conventional strengthening techniques because buildings must be unoccupied before retrofitting, which building owners do not like. To overcome this difficulty, employment of external shear walls and a diaphragm roof level are proposed in this study., A typical pin-connected precast concrete frame and a strengthened structure with the proposed method were tested under-imposed, reversed, cyclic drift of constant rate. The experimental study showed that the proposed method increased lateral stiffness, lateral-load resistance, and seismic energy dissipation and provided a diaphragm effect for the structure.