• Composites Research
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• v.35 no.6
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• pp.425-430
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• 2022

In this study, the mechanical properties of the pressure vessel composite exposed to the thermal environment were evaluated to establish the standard for high temperature static pressure test of the pressure vessel for hydrogen bus. As the tensile strength of the composite material approaches the glass transition temperature of the epoxy resin, the strength decreases due to the deterioration of the epoxy resin. In addition, it was confirmed that the tensile strength increased again due to the post-curing of the epoxy resin during long-term exposure. Therefore, the accelerated stress rupture test conditions of the pressure vessel for the hydrogen bus should be set based on the epoxy resin properties of the carbon fiber composite material.

• Composites Research
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• v.34 no.4
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• pp.241-248
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• 2021

As the electric vehicle market grows, there is an issue of light weight vehicles to increase battery efficiency. Therefore, it is going to replace the battery module cover that protects the battery module of electric vehicles with high strength/high heat-resistant polymer composite material which has lighter weight from existing aluminum materials. It also aims to respond to the early electric vehicle market where technology changes quickly by combining 3D printing technology that is advantageous for small production of multiple varieties without restrictions on complex shapes. Based on the composite material mechanics, the critical length of glass fibers in short glass fiber (GF)/polycarbonate (PC) composite materials manufactured through extruder was derived as 453.87 ㎛, and the side feeding method was adopted to improve the residual fiber length from 365.87 ㎛ and to increase a dispersibility. Thus, the optimal properties of tensile strength 135 MPa and Young's modulus 7.8 MPa were implemented as GF/PC composite materials containing 30 wt% of GF. In addition, the filament extrusion conditions (temperature, extrusion speed) were optimized to meet the commercial filament specification of 1.75 mm thickness and 0.05 mm standard deviation. Through manufactured filaments, 3D printing process conditions (temperature, printing speed) were optimized by multi-optimization that minimize porosity, maximize tensile strength, and printing speed to increase the productivity. Through this procedure, tensile strength and elastic modulus were improved 11%, 56% respectively. Also, by post-processing, tensile strength and Young's modulus were improved 5%, 18% respectively. Lastly, using the FEA (finite element analysis) technique, the structure of the battery module cover was optimized to meet the mechanical shock test criteria of the electric vehicle battery module cover (ISO-12405), and it is satisfied the battery cover mechanical shock test while achieving 37% lighter weight compared to aluminum battery module cover. Based on this research, it is expected that 3D printing technology of polymer composite materials can be used in various fields in the future.

• Composites Research
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• v.34 no.1
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• pp.8-15
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• 2021

In the shipbuilding and marine industry, as a technology for reducing the weight of parts to reduce energy and improve operational efficiency of ships is required, a method of applying fibers-reinforced composites which is high-strength lightweight materials, as part materials can be considered. In this study, the possibility of applying fibers-reinforced composites to the pipe support clamps was evaluated to reduce the weight of LNGC. The fibers-reinforced composites were manufactured using carbon fibers and glass fibers as reinforcing fibers. Through the computer simulation program, the properties of the reinforcing materials and the matrix materials of the composites were inversely calculated, and the performance prediction was performed according to the change in the properties of each fiber lamination pattern. In addition, the structural analysis of the clamps according to the thickness of the composites was performed through the finite element analysis program. As a result of the study, it was confirmed that attention is needed in selecting the thickness when applying the fibers-reinforced composites of the clamp for weight reduction. It is considered that it will be easy to change the shape of the structure and change the structure for weight reduction in future supplementary design.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.87-93
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• 2022

To analyze the interfacial property between the fiber and the matrix, work of adhesion was used generally that was calculated by surface energies. In this paper, it was determined what types of contact angle measurement methods were more accurate between static and dynamic contact angle measurements. 4 types of glass fiber and epoxy resin were used each other to measure the contact angle. The contact angle was measured using two types, static and dynamic contact angle methods, and work of adhesion, W_a was calculated to compare interfacial properties. The interfacial property was evaluated using microdroplet pull-out test. Generally, the interfacial property was proportional to work of adhesion. In the case of static contact angle, however, work of adhesion was not consistent with interfacial property. It is because that dynamic contact angle measurement comparing to static contact angle could delete the error due to microdroplet size to minimize the surface area as well as the meniscus measuring error.

• Journal of Adhesion and Interface
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• v.23 no.1
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• pp.1-7
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• 2022

As the wind blades become larger, they tend to be made by mixing glass fiber and carbon fiber, and it is important to increase the properties of the adhesive which adheres the two materials. The physical properties of the adhesive vary depending on the content of the additive and curing conditions. In this study, the change in adhesion strength with the difference between the CNT (Carbon Nanotube) content of the epoxy adhesive and the humidity during curing was evaluated. GFRP and CFRP specimens were prepared and adhered using an epoxy adhesive, and to examine changes in characteristics with carbon nanotube contents and with the humidity during curing of the epoxy adhesive, adhesion strength was evaluated by dividing the difference between carbon nanotube content and humidity. To find out the change with the CNT contents, the intelaminar shear strength (ILSS) test was performed by dividing the contents of the CNT into 0, 0.1, 0.3, 0.5, and 1 wt%, and to confirm the change with the humidity conditions, the adhesive was cured by dividing the humidity by 20, 50, and 80%. From the result of the experiment, the adhesive force decreased when the content was excessively large, although the adhesive property was enhanced by adding CNT to the epoxy adhesive. In addition, it was confirmed that the adhesion characteristics were not changed as the humidity increased.

• Elastomers and Composites
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• v.46 no.3
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• pp.195-203
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• 2011

Eco-friendly materials or bio-composites were made with poly(lactic acid) (PLA) as matrix polymer and kenaf fibers as filler. Also, acetylated kenaf fibers and compatibilizer were adopted in order to improve the interfacial adhesion between fiber and polymer. In this study, the effect of chemical modification and compatibilizer on the mechanical-viscoelastic and morphology properties of the bio-composites was discussed. The hydrophobic fibers by acetylation were known to show better interfacial bonding with the matrix polymer and resulted in improved performance and morphology. Viscoelastic property and glass transition temperature, however, were not nearly enhanced.

• KSBB Journal
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• v.13 no.5
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• pp.502-510
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• 1998

Stabilization of antibody, which is specific to Salmonella typhimurium antigens, present in dry states on membranes was accomplished, and its shelf-life, i.e., duration for maintaining minimum 90% of the initial activity, under optimal conditions was determined. To prepare two major components of an immuno-strip, the antibody was not only immobilized on nitrocellulose membrane surfaces but also placed within the pores of glass fiber membrane after conjugating it with old colloids as signal generator. Among potential stabilizers of the immuno-components, a disaccharide, trehalose, showed a significant protection effect of immunoglobulin structure from thermal energy. Optimal concentrations of trehalose for the respective component were significantly different (8-fold higher for the antibody-gold conjugate than for the immobilized antibody), which probably resulted from distinct densities and configurations of antibody present on the membranes. An additional requirement for the gold conjugate was freeze-drying of this substance such that the conjugate can be readily resolubilized upon contact with aqueous medium. By using the components prepared under optimal conditions, immuno-strips were constructed and exposed to thermal energy. Signals with less than 10% decrease in the intensity were maintained for approximately 21 days at 60$^{\circ}C$. Compared to previous reports, this result represented a 2-year shelf-life at room temperature. it was, however, two times longer if determined from thermal acceleration tests based on the theory of inactivation rate of protein. Such discrepancy between the two estimates could be mainly attributed to errors in accurately controlling temperatures and also to changes in the physical properties of membranes due to a high thermal energy.

• Structural Engineering and Mechanics
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• v.43 no.6
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• pp.823-833
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• 2012

An experimental method was suggested for obtaining fracture toughness ($K_{Ic}$) and the tensile strength (${\sigma}_t$) of chopped strand glass fiber reinforced polymer concretes (PC). Semi-circular bend (SCB) specimens subjected to three-point bending were used for conducting the experiments on the PC material. While the edge cracked SCB specimen could be used to evaluate fracture toughness, the tensile strength was obtained from the un-cracked SCB specimen. The experiments showed the practical applicability of both cracked and un-cracked SCB specimens for using as suitable techniques for measuring $K_{Ic}$ and ${\sigma}_t$ in polymer concretes. In comparison with the conventional rectangular bend beam specimen, the suggested SCB samples need significantly less material due to its smaller size. Furthermore, the average values of ${\sigma}_t$ and $K_{Ic}$ of tested PC were approximately 3.5 to 4.5 times the corresponding values obtained for conventional concrete showing the improved strength properties of PC relative to the conventional concretes.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.1
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• pp.1-8
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• 2014

Pultruded glass fiber reinforced polymeric plastic (PFRP) and FRP member manufactured by sheet molding compound (SMC) have superior mechanical and physical properties compared with those of conventional structural materials. Since FRP has an excellent corrosion-resistance and high specific strength and stiffness, the FRP material may be highly appreciated for the development of floating-type photovoltaic (PV) power generation system. In this paper, advanced floating PV generation system made of PFRP and SMC is designed. In the design, it includes tracking solar altitude by tilting photovoltaic arrays and tracking solar azimuth by spinning structures. Moreover, the results of the finite element analysis (FEA) are presented to confirm stability of entire structure under the external loads. Additionally, installation procedure and mooring systems in the Hap-Cheon Dam are discussed and the measurement of strain under the actual circumstances is conducted for assuring stability of actually installed structures. Finally, by comparison with allowable stress, appropriate safety of structure is confirmed to operate the system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1337-1347
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• 2013

The parametric analysis on ultimate behavior of buried cylindrical GFRP(Glass Fiber Reinforced Polymer) septic tank was presented. Two kinds of F.E. analysis model(soil-spring model and 3D full model) was constructed. The ultimate behavior of septic tank was investigated according to the size of stiffened steel ring and properties of underground soil. Ramberg-Osgood model and Druker-Prager model were used for material nonlinear characteristics of GFRP septic tank and soil, respectively. The diameter and thickness of stiffened steel ring inside septic tank, elastic modulus and internal friction angle of soil were selected for parametric variables. The ultimate behavior of septic tank, load-displacement, axial and hoop strain, were calculated and investigated.