Copper-coated carbon fibers have excellent conductivity and mechanical properties, making them a promising new lightweight functional material. One of the main challenges to their development is the poor affinity between carbon fiber and metals. This paper selects different carbon fibers for copper electroplating experiments to study the effect of carbon fiber properties on the interface bonding performance between the copper plating layer and carbon fibers. It has been found that the interfacial bonding performance between copper and carbon fiber is related to the degree of graphitization of carbon fiber. The lower the degree of graphitization of carbon fiber, the smaller the proportion of carbon atoms with sp2 hybrid structure in carbon fiber, the stronger the interfacial bonding ability between carbon fiber and copper coating. Therefore, carbon fiber with lower graphitization degree is conducive to reducing the falling off rate of copper coating and improving the quality of copper coating, and the conductivity of copper-plated carbon fibers increases with the decrease of graphitization degree of carbon fibers. The conductivity of copper-plated carbon fibers increases by more than six times when the graphitization degree of carbon fibers decreases by 23.9%. This work provides some benchmark importance for the preparation of highquality copper-plated carbon fibers.

The adhesive design of a fast steering mirror transmitting a high power laser is one of the important design elements that affect optical aberration of the mirror surface. In this paper, we designed the adhesive part to avoid the high power laser beam of the FSM system. Stiffness and wavefront error are trade-off relationships and an optical design was derived to maintain the wavefront error of the mirror surface at high temperatures while satisfying the bandwidth of the FSM system. For the optimal design of the mirror bonding position, structural analysis was conducted using ANSYS and wavefront error analysis was performed using Zernike polynomial code. Through those analysis, FSM most effective at an angle 60 degrees and a distance of 46mm.

Composite laminates are used in a wide range of applications including defense, automotive, aviation and aerospace, marine, wind energy, and recreational sporting goods. These composite beams still exhibit problems such as buckling, local deformations, and interlaminar delamination. To overcome these drawbacks, a novel viscoelastic autoclave bonding with tapered epoxy reinforcement polyurethane films is proposed. In existing laminates, compression face wrinkling and interlaminar delamination is caused in the sandwich beam. The unique viscoelastic autoclave spunbond interlayer bonding is designed to prevent face wrinkling and absorb and distribute stresses induced by external loads, thereby eliminating interlaminar delamination in the sandwich beam. Also, the existing special reinforcement causes stress concentrations, and the core is not effectively connected, which directly affects the stiffness of the beam. To address this, a novel tapered epoxy polyurethane reinforcement adhesive film is proposed, whose reinforcement thickness gradually tapers as it enters the core material. This minimizes stress concentrations at the interface, preventing excessive adhesive squeeze-out during the bonding process, and improves the stiffness of the beam. Results indicate the proposed model avoids the formation of micro cracks, interlaminar delamination, buckling, and local deformations, and effectively improves the stiffness of the beam.

In this study, we report the microstructural evolution and shear strength of an Sn-Sb alloy, used for die attach process as a solder layer of backside metal (BSM). The Sb content in the binary system was less than 1 at%. A chip with the Sn-Sb BSM was attached to a Ag plated Cu lead frame. The microstructure evolution was investigated after die bonding at 330 °C, die bonding and isothermal heat treatment at 330 °C for 5 min and wire bonding at 260 °C, respectively. At the interface between the chip and lead frame, Ni3Sn4 and Ag3Sn intermetallic compounds (IMCs) layers and pure Sn regions were confirmed after die bonding. When the isothermal heat treatment is conducted, pure Sn regions disappear at the interface because the Sn is consumed to form Ni3Sn4 and Ag3Sn IMCs. After the wire bonding process, the interface is composed of Ni3Sn4, Ag3Sn and (Ag,Cu)3Sn IMCs. The Sn-Sb BSM had a high maximum shear strength of 78.2 MPa, which is higher than the required specification of 6.2 MPa. In addition, it showed good wetting flow.

AA1050/AA6061/AA1050 layered sheet was fabricated by cold roll-bonding process and subsequently T4 and T6 aging-treated. Two commercial AA1050 sheets of 1 mm thickness and one AA6061 sheet of 2 mm thickness were stacked up so that an AA6061 sheet was located between two AA1050 sheets. After surface treatments such as degreasing and wire brushing, they were then roll-bonded to a thickness of 2 mm by cold rolling. The roll-bonded Al sheets were then processed by natural aging (T4) and artificial aging (T6) treatments. The as roll-bonded Al sheets showed a typical deformation structure, where the grains are elongated in the rolling direction. However, after the T4 and T6 aging treatments, the Al sheets had a recrystallized structure consisting of coarse grains in both the AA5052 and AA6061 regions with different grain sizes in each. In addition, the sheets showed an inhomogeneous hardness distribution in the thickness direction, with higher hardness in AA6061 than in AA1050 after the T4 and T6 age treatments. The tensile strength of the T6-treated specimen was higher than that of the T4-treated one. However, the strength-ductility balance was much better in the T4-treated specimen than the T6-treated one. The tensile properties of the Al sheets fabricated in the present study were compared with those in a previous study.

Changes in the microstructure and mechanical properties of as-roll-bonded AA6061/AA5052/AA1050 threelayered sheet with increasing annealing temperature were investigated in detail. The commercial AA6061, AA5052 and AA1050 sheets with 2 mm thickness were roll-bonded by multi-pass rolling at ambient temperature. The roll-bonded Al sheets were then annealed for 1 h at various temperatures from 200 to 400 °C. The specimens annealed up to 250 °C showed a typical deformation structure where the grains are elongated in the rolling direction in all regions. However, after annealing at 300 °C, while AA6061 and AA1050 regions still retained the deformation structure, but AA5052 region changed into complete recrystallization. For all the annealed materials, the fraction of high angle grain boundaries was lower than that of low angle grain boundaries. In addition, while the rolling texture of the {110}<112> and {123}<634> components strongly developed in the AA6061 and AA1050 regions, in the AA5052 region the recrystallization texture of the {100}<001> component developed. After annealing at 350 °C the recrystallization texture developed in all regions. The as-rolled material exhibited a relatively high tensile strength of 282 MPa and elongation of 18 %. However, the tensile strength decreased and the elongation increased gradually with the increase in annealing temperature. The changes in mechanical properties with increasing annealing temperature were compared with those of other three-layered Al sheets fabricated in previous studies.

본 연구에서는 GFRP(Glass Fiber Reinforced Polymer)를 주 보강근으로 사용하였으며, 정착길이가 없는 시험체를 제작 하여 4점 재하 휨시험을 수행하였다. 각 변수는 공칭지름이며 공칭지름 D13, D16, D19, 총 3가지의 변수로 이루어져있다. 휨 모 멘트는 공칭지름이 커질수록 약24.17%, 45.92% 강도가 증가하였으나 공칭 휨 강도를 고려하였을 때, 인장 강도와는 달리 공칭 지름에 비례하여 유사한 성능을 나타냄을 알 수 있었다. LVDT로 보강근과 콘크리트와의 부착성능을 확인하였고, 그 값은 매우 미미하며 거의 발생 되지 않은 것으로 판단된다. 또한 DIC로 시험체의 처짐을 확인하였으며, 실세 처짐 값과 유사함을 알 수 있었다.

As a filler metal for lowering the melting point of Ag, many alloy metal candidates have emerged, such as cadmium, with zinc, manganese, nickel, and titanium as active metals. However, since cadmium is known to be harmful to the human body, Cd-free filler metals are now mainly used. Still, no study has been conducted comparing the characteristics of joints prepared with and without cadmium. In addition, studies have yet to be conducted comparing the typical characteristics of brazing filler metals with special structures, and the joint characteristics of brazing filler metals with available frames. In this study, the characteristics of junctions of silver-based intercalation metals were compared based on the type of filler metal additives, using a special structure, a filler metal sandwich structure, to protect the internal base metal. The general filler metal was compared using the structure, and the thickness of the filler metal according to the thickness was reached. A comparison of the characteristics of the junction was conducted to identify the characteristics of an intersection of silver-based brazing filler metal and the effect on joint strength. Each filler metal’s collective tensile strength was measured, and the relationship between joint characteristics and tensile joint strength was explored. The junction was estimated through micro strength measurement, contact angle measurement with the base metal when the filler metal was melted, XRD image observation, composition analysis for each phase through SEM-EDS, and microstructure phase acquisition.

Cracks are an inevitable problem during the use of materials, and flexible sensors with self-healing capability are of great importance for applications in wearable devices and skin-like electronic devices. This paper prepared self-healing flexible strain sensors by compounding self-healing polyurethane with carbon nanotubes. First, by changing the ratio of disulfide bonds, a good balance between mechanical properties and self-healing efficiency was achieved in the prepared self-healing polyurethane. The most balanced sample reached 12.28 MPa in tensile strength, after 24 h of self-repair at 30 °C, the tensile strength was 7.75 MPa, and the self-repair efficiency was 63.11%; after 24 h of self-repair at 80 °C, the tensile strength was 11.64 MPa, and the self-repair efficiency reached 94.79%. Then the sensors prepared by compounding with carbon nanotubes showed a good electrochemical response, and both slow and fast repeated bending of the finger wearing the sensors yielded significantly different electrical signal changes, and the sensors were cut off and still had the same function after self-repair at 30 °C, demonstrating their excellent potential for applications in soft robots, wearable devices, etc.

As the time and cost of body repair can be greatly incurred due to differences in individual technologies, body repair technology should be discussed based on data on general working standards and costs, and as new material technology is applied to the body, continuous learning and experiment on vehicle body repair technology is essential. Since the left and right apron and side members with SPR bonding technology are made of different materials, aluminum and high-strength steel, the restoration of the left and right apron side members should be considered technically, as well as safety and environmental pollution. In this study, we experiment with heterogeneous apron and side members applied with SPR bonding and analyze the results.

This study investigated variables for improving adhesive strength using laser surface treatment when bonding dissimilar materials using adhesives. adhesive strength analysis was performed for CFRP and Al6061 by laser irradiation intensity, and surface roughness was measured to analyze the related results. In the case of CFRP, the adhesive strength was good when the surface was not treated. In the case of Al6061, the adhesive strength was 25 MPa when the surface was treated with 20W, the maximum output of the laser surface treatment equipment, and the adhesive strength was improved by 125% compared to the untreated specimen. In addition, by measuring the surface roughness in the experiment, it was confirmed that the higher the surface roughness, the better the adhesive strength.

To cope with automobile exhaust gas regulations, ISG (Idling Stop & Go) and charging control systems are applied to HEVs (Hybrid Electric Vehicle) for the purpose of improving fuel economy. These systems require quick charge/discharge performance at high current. To satisfy this characteristic, improvement of the positive electrode plate is studied to improve the charge/discharge process and performance of AGM(Absorbent Glass Mat) lead-acid batteries applied to ISG automotive systems. The bonding between grid and A.M (Active Material) can be improved by applying the Sand-Blasting method to provide roughness to the surface of the positive grid. When the Sand-Blasting method is applied with conditions of ball speed 1,000 rpm and conveyor speed 5 M/min, ideal bonding is achieved between grid and A.M. The positive plate of each condition is applied to the AGM LAB (Absorbent Glass Mat Lead Acid Battery); then, the performance and ISG life characteristics are tested by the vehicle battery test method. In CCA, which evaluates the starting performance at -18 oC and 30 oC with high current, the advanced AGM LAB improves about 25 %. At 0 oC CA (Charge Acceptance), the initial charging current of the advanced AGM LAB increases about 25 %. Improving the bonding between the grid and A.M. by roughening the grid surface improves the flow of current and lowers the resistance, which is considered to have a significant effect on the high current charging/discharging area. In a Standard of Battery Association of Japan (SBA) S0101 test, after 300 A discharge, the voltage of the advanced AGM LAB with the Sand-Blasting method grid was 0.059 V higher than that of untreated grid. As the cycle progresses, the gap widens to 0.13 V at the point of 10,800 cycles. As the bonding between grid and A.M. increases through the Sand Blasting method, the slope of the discharge voltage declines gradually as the cycle progresses, showing excellent battery life characteristics. It is believed that system will exhibit excellent characteristics in the vehicle environment of the ISG system, in which charge/discharge occurs over a short time.

To investigate the effect of gas dispersing carbon nanotubes (CNTs) and hot pressing method on the transparency and the conductivity of thin films, the free arc was used to disperse the CNTs in a high dispersion rate, and the dispersed CNTs were rapidly pressed into the surface of the PET film by hot pressing to obtain electrical conductivity. The relationship between the light transmission and sheet resistance of the film was studied by changing the deposition time and the presence or absence of electrostatic adsorption. It was found that the CNTs modified film still retains good electrical conductivity (sheet resistance up to 6 × 104 Ω, light transmittance 69%) through the cleaning of surfactants and ultrasonic waves, which proves that hot pressing is a simple physical method to achieve effective combination of CNTs and films.

In this study, an experimental study was carried out to evaluate the bond shear performance according to the shear connector between the glue-laminated timber and steel interface. Ten block shear specimens were fabricated according to the configuration of the adhesive surface of wood and steel. In addition, four test specimens were produced according to the main variable shape of the wood-concrete shear connector. As a result of the block shear test, the shear strength of the steel-wood adhesive is shown to have a shear performance greater than the wood-wood shear strength. As a result of the push-out test according to the shape of the shear connector, the shear strength increased linearly with the attachment area. The complete composite behavior between the glued-laminated timber and the steel can be secured.

Mechanically enhanced supramolecular carbon nanotube (CNT) films were prepared in water by employing the π-electronrich phenyl, naphthalenyl, and pyrenyl end-functionalized polyethylene oxides (PEOs) as supramolecular linkers, followed by vacuum filtration. Among them, the supramolecular CNT film produced by the pyrenyl end-functionalized PEO (PEOPy) exhibited the highest mechanical strength, which was ~ 1.5–2 times higher than that of the CNT films produced using the typical dispersant, Triton X-100, although the functionality of PEO-Py was lower than that prepared using other linkers, and the content of PEO-Py in the CNT films was lower than that obtained using Triton X-100. Fluorescence and UV–Vis spectroscopy demonstrated that the improved mechanical properties of the supramolecular CNT film result from the formation of π–π interactions between the CNT and the pyrene moieties of the PEO-Py linker. Finally, the supramolecular CNT film exhibited a 40–50 dB electromagnetic shielding efficiency through hybridization with silver nanowires.

최근에 국내에는 다양한 원인에 의한 구조물의 안정성을 우려하는 사회적인 관심이 생겼으며 이에 따른 구조물의 보수·보강에 다양한 연구가 진행되고 있다. 우리나라는 4계절이 뚜렷하며 특히 겨울과 봄에는 일교차가 심하게 발생하는 특징이 있다. 이러한 날씨는 철근콘크리트 구조물에게 동결융해작용을 발생시켜 성능저하의 원인이 되며 구조물의 안정성을 위협할 수 있다. 현재 구조물 보수·보강 방법으로는 탄소섬유나 유리섬유로 FRP(Fiber Reinforced Polymer)를 활용하여 Plate나 Sheet 형태의 부착 보강하는 방법이 일반화 되어있다. 하지만 다소 고가이며 유리섬유는 인체에 유해하다는 연구결과가 있다. 때문에 본 연구에서는 친환경적이고 내열성이 우수한 현무암섬유(Basalt Fiber)를 활용하여 동결융해 작용에 의한 콘크리트의 성능저하를 조건으로 BFRP-콘크리트의 부착성능 및 파괴패턴을 비교 분석하였다. 동결융해시험에 따른 부착강도평가는 동일한 섬유와 수지가 함침된 BFRP를 활용하여 동결융해Cycle(0, 100, 200, 300)과 콘크리트 압축강도(24MPa, 30MPa)를 변수로 부착성능을 평가하였으 며 Case1(선 부착 후 동결융해)과 Case2(선 동결융해 후 부착)로 나누어 진행하였다. Case1과 2 모두 콘크리트 파괴의 형태를 보 였으며 Case2의 경우 Case1에 비하여 부착강도가 감소됨을 나타내었고 동결융해 Cycle이 진행될수록 콘크리트 계면의 성능은 저하되고 부착강도는 평균 약 25%정도 감소하는 것을 확인하였다.