• Steel and Composite Structures
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• 제11권6호
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• pp.435-454
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• 2011

Bonding composite materials to structural members for strengthening purpose has received a considerable attention in recent years. The major problem when using bonded FRP or steel plates to strengthen existing structures is the high interfacial stresses that may be built up near the plate ends which lead to premature failure of the structure. As a result, many researchers have developed several analytical methods to predict the interface performance of bonded repairs. In this paper, a numerical solution using finite - difference method is used to calculate the interfacial stress distribution in beams strengthened with FRP plate having a tapered ends with different thinning profiles. These latter, can significantly reduce the stress concentration. In the present theoretical analysis, the adherend shear deformations are taken into account by assuming a parabolic shear stress through the thickness of both beam and bonded plate. Numerical results from the present analysis are presented to demonstrate the advantages of use the tapers in design of strengthened beams.

• 한국안전학회지
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• 제34권4호
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• pp.76-84
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• 2019

The precast pannels are used as formwork in Half-depth precast deck systems. Therefore, it has many advantages, including safe and convenient construction and reduced construction period compared to cast-in-place construction method. In half-depth precast deck systems, the bonding of precast pannels to cast-in place concrete is very important. To enhance the performance of half-depth precast deck system, it is necessary to improve the composite efficiency of the interface or increase the stiffness of the precast pannel to reduce deformation or stress on the interface. In this study, a flexural test of half-depth precast deck system was performed, in which the shear connecting reinforcement was applied to increase the bonding performance at the interface, and the rib shape precast panels were applied to improve stiffness. In addition, the safety and serviceability of these systems were evaluated. Test results show that all of specimens have the required flexural strength under the ultimate strength limit design. It was also evaluated to have sufficient safety for the serviceability of deflection and crack under the serviceability limit design.

• ETRI Journal
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• 제36권3호
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• pp.343-351
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• 2014

For the fine-pitch application of flip-chip bonding with semiconductor packaging, fluxing and hybrid underfills were developed. A micro-encapsulated catalyst was adopted to control the chemical reaction at room and processing temperatures. From the experiments with a differential scanning calorimetry and viscometer, the chemical reaction and viscosity changes were quantitatively characterized, and the optimum type and amount of micro-encapsulated catalyst were determined to obtain the best pot life from a commercial viewpoint. It is expected that fluxing and hybrid underfills will be applied to fine-pitch flip-chip bonding processes and be highly reliable.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.144-148
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• 2001

A proper estimation of the mechanical properties for composites has been required for better design/selection of constituents for composite materials. Present investigation shows the simulation results for ceramic reinforced metal matrix composite under uniaxial transverse tensile loading. The resulting transverse mean stress with the transverse mean strain was described for composites as a function of the volume fraction with two different types of interfacial bonding: (1)strongly bonded interface, and (2)no bonded interface. A two-dimensional finite element modeling and analysis were conducted based on the unit-cell concept with an assumption of a regular square arrangement of the reinforcement within the composite. The mean stress was generally increased with the ceramic volume fraction for composite with strong interface bonding. The micromechanics concept combined with finite element modeling for composite can be used in order to predict the transverse properties of composites with a priori known properties of constituents.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.304-309
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• 2004

As it is difficult to construct a micro-fluidic system composed of micro-mixers, micro-channels and/or micro-chambers in a single process, an assembly process is typically used. The assembling and bonding of micro-parts, however, introduces other problems. In this work, a virtual assembly process was developed that can be used to design various micro-fluidic systems before actual fabrication commences. In the process, the information required for the micro-stereolithography process is generated automatically. Consequently, complex micro-fluidic systems can be fabricated in a single process, thereby avoiding the need for additional assembly or bonding processes. Using the developed process, several examples were fabricated.

• 한국정밀공학회지
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• 제19권11호
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• pp.211-220
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• 2002

Optical disk drives read information by replacing a laser beam on the disk track. As information has become larger, the more accurate position control of a laser beam is necessary. In this paper, we report the analysis and fabrication of the micro mirror for optical disk drivers. A coupled simulation of gas flow and structural displacement of the micro mirror using the Finite-Element-Method is applied to this. The mirror was fabricated by using MEMS technology. Especially, the process using the lapping and polishing step after the bonding of the mirror and electrode plates was employed for the Process reliability. The mirror size was 2.5mm${\times}$3mm and it needed about 35V for displacement of 3.2 ${\mu}$.

• Journal of Welding and Joining
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• 제24권5호
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• pp.43-48
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• 2006

This paper is concerned with a fracture strength study of composite adhesive lap joints. The tests were carried out on specimen joints manufactured hybrid stacked composites such as the polyester and bamboo natural fiber layer. The main objective of the work was to test the fracture strength using hybrid stacked composites with a polyester and bamboo natural fiber layer. Tensile and peel strength of hybrid stacked composites are tested before appling adhesive bonding. From results, Natural fiber reinforced composites have lower tensile strength than the original polyester. and The load directional orientation and small amount and low thickness of bamboo natural fiber layer have a good effect on the tensile and peel strength of natural fiber reinforced composites. The failure strength of these materials applied adhesive bonding is also affected by fiber orientation and thickness of bamboo natural fiber layer. There for, Fiber orientation of bamboo natural fiber layer have a great effect on the tensile-shear strength of natural fiber reinforced composites including adhesive bonded joints.

• Smart Structures and Systems
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• 제5권5호
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• pp.547-564
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• 2009

Based on the theory of piezoelasticity, an analytical solution for a typical multilayer piezoelectric composite cantilever is obtained by the Airy function method. The piezoelectric cantilever may consist of any number of layers. Moreover, the material and thickness for different layers may be different. The solution obtained in the present paper is concise and can be easily applied for the bending analysis of multilayer piezoelectric actuators considering the effect of bonding layers and electrodes. At last, a comprehensive parametric study is conducted to show the influence of electromechanical coupling (EMC), the number of piezoelectric layers, the elastic modulus of elastic layer and the thickness ratio on the bending behavior of actuators. Some interesting results for the design of multilayer piezoelectric actuators are presented.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.45-47
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• 2006

Lightweight design, safety, vibration, energy absorption capability can no longer achieve without adhesive bond joint. Base on those concepts and cost reduction, adhesive bond FEM model development has been done. The FEM analysis and experiments were conducted in this study. Crash condition is 143 Kg Hammer weight and unit meter Height. and then These test results were used to develop resonable FEM model. To estimate which FEM model is resonable, compare hybrid joint specimen experiment results with FEM analysis results. Conclusively this study achieves optimization bonding model related crash and adhesive bond jointed hat profile crash characters.

• 한국분무공학회지
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• 제13권4호
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• pp.193-199
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• 2008

Spray coating is a versatile surface modification technology in which coating is built-up based on the successive deposition of micron-scaled particles. Depending on the coating materials, the coatings can meet the required mechanical properties, corrosion resistance, and other properties of base materials. Spraying processes are mainly classified into thermal and kinetic spraying according to their bonding mechanism and deposition characteristics. Specifically, thermal spraying process can be further classified into many categories based on the design and mechanism of the process, such as frame spraying, arc spraying, atmospheric plasma spraying (APS), and high velocity oxygen-fuel (HVOF) spraying, etc. Kinetic spraying or cold gas dynamic spraying is a newly emerging coating technique which is low-temperature and high-pressure coating process. In this paper, overall view of thermal and kinetic spray coating technologies is discussed in terms of fundamentals and industrial applications. The technological characteristics and bonding mechanism of each process are introduced. Deposition behavior and properties of technologically remarkable materials are reviewed. Furthermore, industrial applications of spray coating technology and its potentials are prospected.