• Fibers and Polymers
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• 제5권3호
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• pp.239-244
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• 2004

Solution-cast films of polymethylmethacrylate (PMMA) and polyurethane (PU) containing polymeric styryl dye up to 5 % by weight were prepared to investigate their acid-sensitivity and mechanical and thermal properties. Original red samples due to styryl dye turned out yellow very rapidly as they were exposed to acid vapor of hydrochloric acid or p-toluenesulfonic acid. According to UV/VIS spectroscopic measurements, characteristic peak intensities near 430 nm and 520 nm increased or decreased relatively with exposed amounts of acid, respectively. Both PMMA and PU samples showed uniform color distribution due to a good miscibility between polymer and dye which can be evidenced by measurements of glass transition temperature. No significant difference in acid-sensitivity was found between PU and PMMA except relative absorbance. However, dependence of their mechanical properties on dye content was somewhat different with PU or PMMA. In case of PMMA, modulus and breaking stress increased up to about 50 % with increasing dye content, whereas those of PU samples showed only slight increase. It was ascribed to whether the matrix polymer was in the glassy or rubbery state.

• Fibers and Polymers
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• 제5권3호
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• pp.245-251
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• 2004

Poly(trimethylene terephthalate-co-trimethylene 2,6-naphthalate)s (P(TT-co-TN)s) with various copolymer composition were synthesized, and their chain structure, thermal property and crystalline structure were investigated by using $^1$H-NMR spectroscopy, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), respectively. It was found from sequence analysis that all the P(TT-co-TN) copolymers synthesized have a statistical random distribution of TT and TN units. It was also observed from DSC thermograms that the glass transition temperature increases linearly with increasing the TN comonomer content, whereas the melting temperature of copolymer decreases with increasing the corresponding comonomer content in respective PTT- and PTN-based copolymer, showing pseudo-eutectic melting behavior. All the samples melt-crystallized isothermally except for P(TT-co-66 mol % TN) exhibit multiple melting endotherms and clear X-ray diffraction patterns. The multiple melting behavior originates from the dual lamellar population and/or the melting-recrystallization-remelting. The X-ray diffraction patterns are largely divided into two classes depending on the copolymer composition, i.e., PTT and PTN $\beta$-form diffraction patterns, without exhibiting cocrystallization.

• Korean Chemical Engineering Research
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• 제43권6호
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• pp.691-695
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• 2005

종이 필터, 면섬유, 유리섬유 필터 등과 같은 지지체 위에 이차성장 수열합성법에 의하여 제올라이트 박막을 제조하였다. 먼저, 제올라이트 종자로 사용하기 위하여 제올라이트 NaA(${\approx}0.5{\mu}m$)와 silicalite-1(${\approx}0.2{\mu}m$) 결정들을 합성하였고, 이 결정들을 지지체의 표면에 화학결합을 이용하여 부착시켰다. 종자 결정으로 덮힌 지지체 위에 NaA나 silicalite-1 제올라이트 박막이 생성되었으며, 제조된 박막은 주사형 전자현미경으로 관찰하였고, X-ray 회절로 분석하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.93-102
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• 2007

FRP바닥판은 경량이기 때문에 신속한 시공이 가능하고, 고정하중을 경감시킬 수 있다는 장점이 있어 전 세계적으로 시공 실적이 점차 증가하고 있다. 본 논문에서는 효과적인 FRP바닥판의 적용을 위하여 유한요소해석을 통하여 FRP바닥판을 구성하는 부재별 적정 형상비를 결정하였으며, 향후 FRP바닥판 설계시 기초자료로 활용할 수 있도록 하고자 하였다. 또한, FRP의 이방적 재료 특성과 복잡한 제약조건을 고려한 FRP바닥판의 최적설계를 수행하였으며, 그 결과를 토대로 제안된 FRP바닥판의 기본 단면 형상에 대한 검증을 수행하였다.

• 한국안전학회지
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• 제26권6호
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• Steel and Composite Structures
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• 제12권1호
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• pp.53-72
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• 2012

In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of $({\pm}45)_s$ model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.137-140
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• 2006

In this study, a seismic performance of reinforced concrete columns strengthened by a sprayed fiber reinforced polymer (SFRP) is investigated. For this purpose, six column specimens approximately scaled into 2/3, are designed and tested under a constant axial load, 10% of the nominal axial strength of column, and pseudo-static reversed cyclic lateral loading system. Four specimens are strengthened by Sprayed FRP using different combinations of short fibers (carbon or glass fiber) and resins (epoxy or vinyl esther). For comparison, the test investigated in this study also includes a specimen strengthened using carbon fiber reinforced polymer (CFRP), and also a control specimen without strengthening. The results revealed that specimens strengthened using SFRP showed a improved structure behavior, compared to control specimen, in terms of strength, ductility, lateral drift capacity, and energy-absorbtion capacity. In addition, compared to the specimen strengthened using CFRP, Sprayed FRP-strengthened specimens reasonably showed a equivalent seismic performance.

• 한국초전도ㆍ저온공학회논문지
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• 제24권1호
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• pp.8-12
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• 2022

Recently, research on applying composite materials to various industrial fields is being actively conducted. In particular, composite materials fabricated by Fused Deposition Modeling 3D printers have more advantages than existing materials as they have fewer restrictions on manufacturing shape, reduce the time required, weight. With these advantages, it is possible to consider utilizing composite materials in cryogenic environments such as the application of liquid oxygen and liquid hydrogen, which are mainly used in an aerospace and mobility. However, FDM composite materials are not verified in cryogenic environments less than 150K. This study evaluates the characteristics of composite materials such as tensile strength and strain using a UTM (Universal Testing Machine). The specimen is immersed in liquid nitrogen (77 K) to cool down during the test. The specimen is fabricated using 3D print, and can be manufactured by stacking reinforced fibers such as carbon fiber, fiber glass, and aramid fiber (Kevlar) with base material (Onyx). For the experimental method and specimen shape, international standards ASTM D638 and ASTM D3039 for tensile testing of composite materials were referenced.

• 한국산업융합학회 논문집
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• 제26권1호
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• pp.201-209
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• 2023

Recently, fiber-reinforced composites have been widely used in various industrials fields. In this study, the mechanical behavior, especially fracture behavior, of biomimetic fiber-reinforced composites subjected to pressure loading was analyzed using finite element analysis (FEA). The fiber alignments in the biomimetic composites formed a helicoidal structure, wherein a stacking sequence involved a gradual rotation of each ply in the multi-layered laminated composites. For comparison, cross-ply composite samples with fibers arranged at 0° and 90° were prepared and analyzed. In addition, the mechanical behavior was analyzed based on combinations of the stacking sequence of carbon-fiber composites and glass-fiber composites. The FEA results showed that, when compared with the cross-ply samples, the mechanical properties of the biomimetic composites were considerably improved under pressure loading, which was applied to one side of the composites. Thus, the biomimetic helicoidal structure significantly improved the mechanical properties of the composites. Placing materials having high elasticity and strength in the outermost layers (the layer of the side on which pressure was applied and the opposite side layer) of the composites also significantly contributed to improving the mechanical properties of the composites.

• Steel and Composite Structures
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• 제47권3호
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• pp.395-403
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• 2023

The main objective of this article is to investigate the response of different fiber metal laminates subjected to low velocity impact experimentally and numerically via finite element method (FEM). Hence, two different fiber metal laminate (FML) samples (GLARE/CARALL) are made of 7075-T6 aluminum sheets and polymeric composites reinforced by E-glass/carbon fibers. In order to study the responses to the low velocity impacts, samples are tested by drop weight machine. The projectiles are released from 1- and 1.5-meters height were the speed reaches to 4.42 and5.42 meter per second and the impact energies are measured as 6.7 and 10 Joules. In addition to experimental study, finite element simulation is done and results are compared. Finally, a detailed study on the maximum deflection, delamination and damages in laminates and geometry's effect of projectiles on the laminate response is done. Results show that maximum deflection caused by spherical projectile for GLARE samples is more apparent in comparison with the CARALL samples. Moreover, the maximum deflection of GLARE samples subjected to spherical projectile with 6.7 Joules impact energy, 127% increases in comparison with the CARALL samples in spite of different total thickness.