• Composites Research
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• v.22 no.5
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• pp.30-36
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• 2009

The failure strengths and modes in carbon fiber reinforced polymeric composites, with two serial bolt-fastened composite joints, were investigated to evaluate the typical joint configurations of composite components. The parametric studies were performed experimentally at room temperature dry and elevated temperature wet, $82.2^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, two basic load-displacements curves are observed. Each failure mode has the characteristic curve. It is showed that the bearing failure mode occurs in elevated temperature wet condition. It is analysed that the strength of bearing failure mode is not highly depending on the effective modulus of specimen. The failure strength at elevated temperature wet is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.503-510
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• 2009

Latex modified concrete (LMC) is a successful polymer-portland cement concretes, which have been developed and used for many years, in overlaying bridge decks and resurfacing industrial floors. The excellent bond strength to substrate, easy application and high resistance to impact, abrasion, wear, aggressive chemicals and freeze-thaw deterioration have made this material used widely. The objective of this study was to determine experimentally the load-deflection response and ultimate strength of reinforced RC beams. The cracking patterns and the mode of failure were observed. Because of excellent bond strength and repairing effects, the RC beams repaired by LMC at compression or tension zone showed over 100% recovery from damaged structures. The RC beams overlaid by LMC showed significant improvement at load carrying capacity as overlay thickness increases. However, the beams repaired of tension zone without shear stirrups almost showed no strengthen effect, and indicated an interfacial failures. The interfacial behavior was estimated by numerical method adopting the concept of shear flow.

• Composites Research
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• v.36 no.1
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• pp.37-41
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• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Composites Research
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• v.22 no.3
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• pp.82-88
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• 2009

The effect of open and filled holes on the strength behavior of carbon fiber reinforced polymeric (CFRP) composites was investigated. The strength was measured at room temperature dry, cold temperature dry, $-55^{\circ}C$, and elevated temperature wet, $108.3^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, it is shown that the filled hole tensile strength is larger than that of open hole by reducing damage around the hole due to the constraint imposed by the fastener. The tensile strength at cold temperature dry, $-55^{\circ}C$ is increased with the brittleness by the thermal expansion coefficient of fiber and matrix. The compressive strength at elevated temperature wet, $108.3^{\circ}C$ is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• Composites Research
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• v.21 no.2
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• pp.1-7
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• 2008

Composite materials are currently used in aero-space industry, sport and leisure industry but it has many problems such as mechanical properties deterioration by moisture absorption. In this study, we appraised interlaminar shear strength with specimen that immersed/ immersed-dried in water environment(distilled/sea) during $100{\sim}200$days. In the result, properties degradation of resin part and silan part by moisture absorption is judged early on main cause of interlaminar shear strength, and later destruction of mechanical bonding between silan part and fiber by moisture absorption is Judged later main cause of interlaminar shear strength. In conclusion, the recovery of interlaminar shear strength is judged to difficult due to interfacial destruction by moisture when pass over irreversible by moisture in composite material.

• Composites Research
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• v.22 no.3
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• pp.60-65
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• 2009

The mechanical behavior of carbon fiber reinforced polymeric (CFRP) composites was investigated. Both strength and modulus were measured at room temperature dry, cold temperature dry, $-55^{\circ}C$, and elevated temperature wet, $82.2^{\circ}C$ on seven different laminate configurations consisting of $[0_6]_T$, $[90_{12}]_T$, $[0_{16}]_T$ and $[90_{16}]_T$ unidirectional laminates, $[{\pm}45]_{5S}$ angle-ply laminate, $[0/90_{12}/0]_T$ cross-ply laminate, a 36-ply laminate $[0/45/-45/45/-45/0]_{3S}$. Based on the experimental data presented, it is shown that the strength at cold temperature dry, $-55^{\circ}C$ is increased with the brittleness of fiber or matrix. Moreover, it is shown that both shear strength and modulus at elevated temperature wet, $82.2^{\circ}C$ are decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• Journal of Adhesion and Interface
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• v.10 no.3
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• pp.134-140
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• 2009

The acrylic copolymers with variation in side chain were synthesized based on molecular design. Wettability and adhesion properties on the wafer surface were investigated for these acrylic copolymer pressure sensitive adhesives. Three-dimensional networks of linear acrylic copolymers were produced with epoxy-type Tetra-DX cross-linking agent. The effect of cross-linking on adhesion characteristics was investigated. The side chain of acrylic copolymer played more important role in wettability than the interfacial interaction. As the degree of cross-linking increased, both probe tack and peel strength decreased. Also, heat resistance measured by SAFT increased with cross-linking; however, it showed the deterioration when excess cross-linking agent was added.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.348-351
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• 2006

Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below $19m{\Omega}cm^2$ under the compress force of $150N/cm^2$. It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. $9{\mu}A/cm^2$ to ca. $0.5{\mu}A/cm^2$ in the mixed solution of $0.1N\;N_2SO_4$ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and $0.75V_{SCE}$ for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than $1{\mu}A/cm^2$ for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.

• Composites Research
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• v.35 no.4
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• pp.248-254
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• 2022

In this study, TiB₂-steel composite with high-fractional TiB₂ reinforcement was fabricated by gas pressure infiltration process and the microstructure analysis and compressive strength and hardness were evaluated. To elucidate the correlation between microstructure and mechanical properties for fabricated composite, after the compression test of TiB₂-steel composite, the fracture surface was analyzed and the fracture behavior on compression test was predicted. As a result of the compression fracture surface analysis, interfacial failure trace between the steel matrix and the reinforcement was observed, and the interface between the steel matrix and the reinforcement was analyzed using TEM. From the result of microstructure analysis on the fabricated composite, it was confirmed that, in addition to TiB₂ reinforcement and steel matrix, TiC phase and coarse (Fe,M)₂B (M=Cr,Mn) phase were formed. Throughout the thermodynamic calculation, it was confirmed that TiC and (Fe,M)₂B can be formed as a stable phase under the process condition. The fabricated TiB₂-steel composite had a significantly increased hardness, and the compressive strength and Young's modulus were improved by 3.07 times and 1.95 times, respectively, compared to steel matrix. It seems that the coarse (Fe,M)₂B (M=Cr,Mn) phase formed throughout the composite causes the deterioration of mechanical properties, and by controlling the formation of the (Fe,M)₂B (M=Cr,Mn) phase, it is judged that the mechanical properties of the TiB₂-steel composite can be further improved.