• Smart Structures and Systems
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• v.20 no.4
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• pp.441-450
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• 2017

The objective of this work is to present a conceptual design and the modelling of a distributed sensor system based on fiber optic devices (Fiber Bragg Grating, FBG), aimed at measuring span-wise and chord-wise variations of an adaptive (morphing) trailing edge. The network is made of two different integrated solutions for revealing deformations of the reference morphing structure. Strains are confined to typical values along the span (length) but they are expected to overcome standard ranges along the chord (width), up to almost 10%. In this case, suitable architectures may introduce proper modulations to keep the measured deformation low while preserving the information content. In the current paper, the designed monitoring system combines the use of a span-wise fiber reinforced patch with a chord-wise sliding beam. The two elements make up a closed grid, allowing the reconstruction of the complete deformed shape under the acceptable assumption that the transformation refers to regular geometry variations. Herein, the design logic and some integration issues are reported. Preliminary experimental test results are finally presented.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.295-322
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• 2013

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.296-302
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• 2010

If the fiber reinforced plastic is exposed to the moisture for a long period of time, most of moisture absorption occurs on the resin place, thus dropping cohesiveness between the molecules as the water molecules permeated between high molecular chains grant high molecular mobility and flexibility. Also as the micro crack occurs due to the permeation of moisture on the interface of glass fiber and epoxy resin, it is developed to the overall damage of interface place. Hence, the study on absorption is essential as the mechanical and physical properties of fiber reinforced composites are reduced. However, the study on absorption has the inconvenience needing to expose composite materials to fresh water or seawater for 1 month or up to 1 year. Therefore, this study has exposed fiber reinforced composites to fresh water and has developed a model with an accuracy of 98% after comparing the analysis value obtained by using ANSYS while basing on the experimental value of property decline by absorption and the basic properties of glass fiber and epoxy resin used in the experiment.

• Journal of Radiation Industry
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• v.4 no.3
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• pp.259-263
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• 2010

Carbon fibers are used as a reinforcement material in an epoxy matrix in advanced composites due to their high mechanical strength, rigidity and low specific density. An important aspect of the mechanical properties of composites is associated to the adhesion between the surface of the carbon fiber and the epoxy matrix. This paper aimed to evaluate the effects of electron beam irradiation on the physicochemical properties of carbon fibers to obtain better adhesion properties in resultant composite. Chemical structure and surface elements of carbon fiber were determined by FT-IR, elemental analysis and X-ray photoelectron spectroscopy, which indicated that the oxygen content increased significantly with increasing the radiation dose. Thermal stability of the carbon fibers was studied via the thermalgravimetric analysis. Surface morphology of carbon fiber was analyzed by scanning electron microscope. It was found that the degree of surface roughness was increased by electron beam irradiation.

• Advances in Computational Design
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• v.9 no.3
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• pp.167-186
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• 2024

Implementing isogeometric methodology in micromechanical analysis of composite materials has been recently investigated in some research studies. These research studies are based on multi-patch modeling which requires coupling constraints among the NURBS patches, and the domain decomposition effort in model preparation stage. This approach has been employed for small representative volume elements (RVE). However, small RVE neglects some characteristics of microstructure and larger one increases the number of required NURBS patches in multi-patch framework. As a step forward, this research presents a framework which simulates the RVE using a single NURBS patch. the presented framework has been used to include the effects of fiber distribution and porosities in simulated RVEs. In this regard, heterogeneity and 2D/3D voids within RVE are modeled only by inserting knots and modifying the control points. In addition to beneficial advantages of isogeometric methodology for RVE-based models, this framework simplifies isogeometric modeling of more complicated RVEs by eliminating the domain decomposition stage and avoiding coupling constraints between non-matching patches. The performance of the presented model has been verified by performing micromechanical damage analysis on several generated RVEs of unidirectional fiber-reinforced composites, in which matrix and fiber/matrix interfaces experience damage. The predicted damage evolutions under different loading conditions are in excellent agreement with prior experimental and numerical studies that demonstrate the veracity of the presented model.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.836-843
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• 2003

The polymer composites contain numerous internal boundaries and its structural elements have different responses and different resistances under the same service environment. Fatigue phenomenon is much more complex in composites than homogeneous materials. An understanding of the fracture behavior of polymer composite materials subjected to constant and cyclic loading is necessary for predicting the life time of structures fabricated with polymers. There is a need to acquire a better understanding of the fatigue performance and failure mechanisms of composites under such conditions. Therefore, in this study the analyses of fiber orientation and fracture mechanism for low cycle fatigue crack have been studied by SEM and LM for observing the ultrathin sections.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.727-732
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• 2002

Steel Fiber Reinforced Shotcrete(SFRS) has been prevalently used in lining to stabilize tunnel structures as temporary or permanent support. In recent, it is one of the major elements of tunnel construction, and so the quality control of SFRC should be clarified to guarantee the safety. The experimental study has been performed to verify the possible correlations in several chracteristics related to quality of SFRC and examine the applicability of round panel test for in field. The test variables were the type and dosage of accelerator, aspect ratio of fiber, and fiber content. The test results such as compressive strength, flexural strength, flexural toughness, and energy absorption capacity, were exmained and analyzed scrutinizingly.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.151-158
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• 2002

In the present design concept, the nonlinear behaviour of bridges is at lowed under large earthquake. The nonlinearity is, however, localized like pier, bearing, etc. Especially, pier columns are most important members for seismic performance. It is, however, difficult to solve the problem how the nonlinearity of columns should be modelled. In this study, the fiber element is used for modelling pier column. The element is a kind of structural elements like frame element, and it can model the distributed plasticity of plastic hinge. A 3 span continous bridge is taken for seismic analysis. First, the nonlinear static analysis the column at fixed support are performed so that the characteristics of column is analyzed. Second, Linear and nonlinear dynamic analysises using simplified model for longitudinal direction are carried out and the results are analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1220-1228
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• 1999

In this paper, we deal with an important network design problem in providing multimedia telecommunication services. The problem is to find an optimal gateway location and fiber routing, while minimizing the total cost. The cost elements are the installation cost of add-drop multiplexer and fiber cables. We have developed effective heuristic procedures for the problem. The performance of the developed heuristic shows promising computational results.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.125-142
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• 2016

An overall review of the structural behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC) elements subjected to various loading conditions needs to be conducted to prevent duplicate research and to promote its practical applications. Thus, in this study, the behavior of various UHPFRC structures under different loading conditions, such as flexure, shear, torsion, and high-rate loads (impacts and blasts), were synthetically reviewed. In addition, the bond performance between UHPFRC and reinforcements, which is fundamental information for the structural performance of reinforced concrete structures, was investigated. The most widely used international recommendations for structural design with UHPFRC throughout the world (AFGC-SETRA and JSCE) were specifically introduced in terms of material models and flexural and shear design. Lastly, examples of practical applications of UHPFRC for both architectural and civil structures were examined.