• Composites Research
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• v.31 no.6
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• pp.299-303
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• 2018

In order to improve the interfacial bonding force and reaction polymerization degree of the carbon fiber reinforced nylon 6 composite material, the surface of the existing epoxy-sizing carbon fiber was desized to remove the epoxy and treated with urethane, nylon and phenoxy sizing agent, was observed. The interfacial bond strength of the resized carbon fiber was confirmed by IFSS (Interfacial Shear Strength) and the fracture surface was observed by scanning electron microscope. The results showed that the interfacial bonding strength of the carbon fiber treated with nylon and phenoxy sizing agents was higher than that of urethane - based sizing. It has been found that the urethane - type resizing carbon fiber has lower interfacial bonding strength than the conventional epoxy - sizing carbon fiber. This result shows that the interfacial bonding between carbon fiber and nylon 6 is improved by removing low activity and smoothness of existing carbon fiber.

• Korean Journal of Metals and Materials
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• v.46 no.1
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• pp.33-38
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• 2008

The interfacial reactions and shear strength of pure Sn solder bump were investigated with different under bump metallizations (UBMs) and reflow numbers. Two different UBMs were employed in this study: Cu and Ni. Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) were formed at the bump/Cu UBM interface, whereas only a Ni3Sn4 IMC was formed at the bump/Ni UBM interface. These IMCs grew with increasing reflow number. The growth of the Cu-Sn IMCs was faster than that of the Ni-Sn IMC. These interfacial reactions greatly affected the shear properties of the bumps.

• Composites Research
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• v.19 no.4
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• pp.7-14
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• 2006

Interfacial shear strength between epoxy and carbon fiber has been analyzed utilizing the microbond specimen with an epoxy micro-droplet adhered onto single carbon fiber. The interfacial shear stress distributions along the fiber/matrix interface were calculated by finite element analysis using three kinds of finite element models such as droplet model, circular-crosssection model and pull-out model. Conclusions were obtained as follows. (1) Interfacial shear stress distribution showed that larger stresses were concentrated in the fiber/matrix interface for microbond test than for pull-out test. Thus, debonding at the fiber/matrix interface during microbond test was liable to occur at low load level. (2) Microbond test showed higher interfacial strength which was caused by various effects of micro-droplet geometry and size as well as stress concentration in the region contacting with the micro-vise tip.

• Steel and Composite Structures
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• v.20 no.6
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• pp.1275-1303
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• 2016

Steel plates and carbon-fiber-reinforced polymer (CFRP) laminates or plates bonded to concrete substrates have been widely used for concrete strengthening. However, this technique cause plate debonding, which makes the strengthening system inefficient. The main objective of this study is to enhance the bond strength of externally bonded steel plates and CFRP laminates to the concrete surface by proposing new embedded adhesive and steel connectors. The effects of these new embedded connectors were investigated through the tests on 36 prism specimens. Parameters such as interfacial shear stress, fracture energy and the maximum strains in plates were also determined in this study and compared with the maximum value of debonding stresses using a relevant failure criterion by means of pullout test. The study indicates that the interfacial bond strength between the externally bonded plates and concrete can be increased remarkably by using these connectors. The investigation verifies that steel connectors increase the shear bond strength by 48% compared to 38% for the adhesive connectors. Thus, steel connectors are more effective than adhesive connectors in increasing shear bond strength. Results also show that the use of double connectors significantly increases interfacial shear stress and decrease debonding failure. Finally, a new proposed formula is modified to predict the maximum bond strength of steel plates and CFRP laminates adhesively glued to concrete in the presence of the embedded connectors.

• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.637-646
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• 2016

In this study, slant shear tests for the prism specimens strengthened with ultra-high performance fiber reinforced concrete (UHPFRC), normal- and high-strength concrete were performed to evaluate the interfacial shear strength between old and new concrete substrate. Test parameters are the roughness of surface, concrete strength, and fiber volume fraction of UHPFRC. The surface of the concrete was roughened by shot blasting. Test results showed that the adhesion bond resistance of the specimen with a roughened surface was very large compared to that of the specimen with a smooth surface. In addition, the interfacial shear strength appeared to be affected by the concrete strength rather than the fiber volume fraction. For the roughened surface by shot-blasting method, interfacial shear resistance exceeded the upper limit which is presented in current design codes even if the shear-friction reinforcements are not provided. Based on the test results, it is applicable to use the current concrete design codes to achieve the shear-friction design for the interface between conventional concrete and UHPFRC. However, for the surface which is not processed, it would be appropriate to provide additional shear-friction reinforcement.

• Advances in concrete construction
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• v.15 no.6
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• pp.359-376
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• 2023

Ultra-high-performance concrete (UHPC) has become an attractive cast-in-place repairing material for existing engineering structures. The present study aims to investigate age-dependent high-early-strength UHPC (HESUHPC) material properties (i.e., compressive strength, elastic modulus, flexural strength, and tensile strength) as well as interfacial shear properties of HESUHPC-normal strength concrete (NSC) composites cured at different season temperatures (i.e., summer, autumn, and winter). The typical temperatures were kept for at least seven days in different seasons from weather forecasting to guarantee an approximately consistent curing and testing condition (i.e., temperature and relative humidity) for specimens at different ages. The HESUHPC material properties are tested through standardized testing methods, and the interfacial bond performance is tested through a bi-surface shear testing method. The test results quantify the positive development of HESUHPC material properties at the early age, and the increasing amplitude decreases from summer to winter. Three-day mechanical properties in winter (with the lowest curing temperature) still gain more than 60% of the 28-day mechanical properties, and the impact of season temperatures becomes small at the later age. The HESUHPC shrinkage mainly occurs at the early age, and the final shrinkage value is not significant. The HESUHPC-NSC interface exhibits sound shear performance, the interface in most specimens does not fail, and most interfacial shear strengths are higher than the NSC-NSC composite. The HESUHPC-NSC composites at the shear failure do not exhibit a large relative slip and present a significant brittleness at the failure. The typical failures are characterized by thin-layer NSC debonding near the interface, and NSC pure shear failure. Two load-slip development patterns, and two types of main crack location are identified for the HESUHPC-NSC composites tested in different ages and seasons. In addition, shear capacity of the HESUHPC-NSC composite develops rapidly at the early age, and the increasing amplitude decreases as the season temperature decreases. This study will promote the HESUHPC application in practical engineering as a cast-in-place repairing material subjected to different natural environments.

• Membrane and Water Treatment
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• v.12 no.1
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• pp.37-41
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• 2021

This paper presents the multiscale calculation results of the very fast volume transport in micro/nano cylindrical tubes with the wall slippage. There simultaneously occurs the adsorbed layer flow and the intermediate continuum fluid flow which are respectively on different scales. The modeled fluid is water and the tube wall is somewhat hydrophobic. The calculation shows that the power loss on the tube no more than 1.0 Watt/m can generate the wall slippage even if the fluid-tube wall interfacial shear strength is 1 MPa; The power loss on the scale 104 Watt/m produces the volume flow rate through the tube more than one hundred times higher than the classical hydrodynamic theory calculation even if the fluid-tube wall interfacial shear strength is 1 MPa. When the wall slippage occurs, the volume flow rate through the tube is in direct proportion to the power loss on the tube but in inverse proportion to the fluid-tube wall interfacial shear strength. For low interfacial shear strengths such as no more than 1 kPa, the transport in the tube appears very fast with the magnitude more than 4 orders higher than the classical calculation if the power loss on the tube is on the scale 104 Watt/m.

• Macromolecular Research
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• v.10 no.1
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• pp.24-33
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• 2002

Interfacial and microfailure properties of carbon fiber/epoxy composites were evaluated using both tensile fragmentation and compressive Broutman tests. A monomeric and two polymeric coupling agents were applied via the electrodeposition (ED) and the dipping applications. A monomeric and a polymeric coupling agent showed significant and comparable improvements in interfacial shear strength (IFSS) compared to the untreated case under both tensile and compressive tests. Typical microfailure modes including cone-shaped fiber break, matrix cracking, and partial interlayer failure were observed under tension, whereas the diagonal slipped failure at both ends of the fractured fiber appeared under compression. Adsorption and shear displacement mechanisms at the interface were described in terms of electrical attraction and primary and secondary bonding forces.

• Macromolecular Research
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• v.13 no.5
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• pp.453-459
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• 2005

Natural fiber henequen/unsaturated polyester (UPE) composites were fabricated by means of a compression molding technique using chopped henequen fibers treated at various electron beam (EB) dosages. The interfacial shear strength (IFSS), dynamic mechanical properties, and thermal expansion behavior were investigated through a single fiber microbonding test, fractographic observation, dynamic mechanical analysis, and thermomechanical analysis, respectively. The results indicated that the interfacial and dynamic mechanical properties significantly depended on the level of the EB treatment irradiated onto the henequen fiber surfaces. The effect of EB treatment on the IFSS, storage modulus and fracture surface of the henequen/UPE composites agreed with each other. The results of this study also suggested that the modification of henequen fiber surfaces at 10 kGy EB is the most effective for improving the interfacial properties of the henequen/UPE composites.

• Journal of Adhesion and Interface
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• v.5 no.1
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• pp.21-28
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• 2004

In this work, glass fiber/nylon 6 and woven glass fiber/nylon 6 composites have been fabricated using glass fiber reinforcements sized with 3-chloropropyltrimethoxysilane(CTMS) having a chloropropyl organo-functional group in the molecular chain end. The interfacial shear strength of glass fiber/nylon 6 composite was measured using a single fiber microbonding test and the interlaminar shear strength and the storage modulus of woven glass fabric/nylon 6 composites were measured using a short-warn shear test and a dynamic mechanical analysis, respectively, informing the effect of the concentration of CTMS on the properties. With increasing CTMS concentration, the interfacial properties of the composites were improved. The results on the interfacial shear strength, interlaminar shear strength, interlaminar failure pattern, and storage modulus with varying the CTMS concentration agree with each other.