• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.619-628
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• 2011

Human soft tissues, including muscles, ligaments, skin, and blood vessels, are an interesting subject because damage to them can be observed in everyday life. Besides the lack of available experimental data and the large deformation upon loading, the anisotropic and compressible nature of annulus fibrosus makes it more difficult to find a simple material model. A fiber-reinforced hyperelastic material model is used to determine the stress-strain curves upon uniaxial loading. The energy potential function for annulus fibrosus is composed of three different parts: matrix, fibers, and matrix-fiber interaction, which accounts for the angles between two families of fibers. In this paper, two different types of energy potential function for the matrix are considered, and are inserted into the fiber-reinforced model. The calculated results are compared with the Neo-Hookean model and experimental data, and reasonable agreement is observed overall.

• Composites Research
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• v.23 no.2
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• pp.17-23
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• 2010

The stealth technology can increase the survivability of aircrafts or warships and enhance the capability of mission completion in hostile territory. The purpose of this paper is to present the low observable structure with curved surfaces made by fiber-reinforced composites and to show the possibility of developing omnidirectional stealth platforms for military applications. In this study, we developed a radar absorbing structures(RAS) based on a circuit analog absorber to reduce the radar cross section(RCS) of an object with curved surfaces. Firstly, the RAS with a periodic square patterned conducting polymer layer was designed and simulated using a commercial 3-D electromagnetic field analysis program. Secondly, the designed semi-cylindrical structure with low RCS was fabricated using fiber-reinforced composites and conducting polymer. To make the periodic pattern layer, acts as resistive sheet, the intrinsic conducting polymer paste containing PEDOT with a polyurethane binder was used. Finally, the radar cross section was measured to evaluate the radar absorbing performances of the fabricated RAS by the compact range facility in POSTECH.

• Composites Research
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• v.34 no.1
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• pp.1-7
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• 2021

Fiber-reinforced thermoplastic composites are applied to transport industries to lightweight of body, and applications will be expanded gradually. In this study, the impregnation and mechanical properties of continuous glass fiber (GF) reinforced polycarbonate (PC) composites were evaluated with different molecular weights of PC. The continuous GF reinforced PC composite were prepared by using GF fabric and PC film via continuous compression molding method. The melting flow index and tensile strength of PC matrix were evaluated with different molecular weights. Mechanical properties (tensile, flexural, and compressive) and pore rate of GF/PC composite were evaluated with different molecular weights of PC. The fracture behavior was analyzed to fracture surface of GF/PC composite using FE-SEM images. As these results, it was condition of representing the best mechanical property that the GF/PC composite was prepared by using PC of 20,000 g/mol as matrix.

• Fiber Technology and Industry
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• v.1 no.1
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• pp.37-63
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• 1997

• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.282-289
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• 2014

After being laminated with a combination of glass fiber reinforced plastic and plywood, the GFRP laminated plate was densificated for 1 hour at $150^{\circ}C$ with pressure of $1.96N/mm^2$. A partial reinforced beam was produced by attaching the 5 GFRP laminated plates to the joint of glulam and the column. In addition, the column to beam joint was produced by using reinforced laminated wooden pin which was made of GFRP sheet and plywood, fiber glass reinforced cylindrical-LVL column. The joint was made of round log, glulam and drift pin as the reference specimen, and its moment resistance was evaluated. As a result, the strength performance of specimens with partial reinforced beams were 1.8 times stronger than the reference specimen on average. Furthermore, rupture was neither occurred on partial reinforced beam nor column. Toughness and stiffness of joints were also fine. The GFRP sheet reinforced laminated plate showed better reinforcement effect than GFRP textile reinforced one. GFRP sheet was inserted into each layer of laminate, and it showed good condition in rotation-angle and strength, therefore it is the most appropriate to reinforce the part of the beam.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.103-109
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• 2005

Fiber reinforced plastic material should be inspected in fabrication process in order to enhance quality by prevent defects such as delamination and void. Generally, ultrasonic technique is widely used to evaluate FRP. In conventional ultrasonic techniques, transducer should be contacted on FRP. However, conventional contacting method could not be applied in fabrication process and novel non-contact evaluating technique was required. Laser-based ultrasonic technique was tried to evaluate CFRP plate. Laser-based ultrasonic waves propagated on CFRP were received with various transducers such as accelerometer and AE sensor in order to evaluate the properties of waves due to the variation of frequency. Velocities of laser-based ultrasonic waves were evaluated for various fiber orientation. In addition, laser interferometry was used to receive ultrasonic wave in CFRP and frequency was analysed.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.88-95
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• 1996

유리섬유가 강화된 열가소성 복합재료 판재의 성형성에 대한 이해를 돕기 위해 이론적 고찰과 실험적 고찰이 행해졌다. 성형시험에서 사용된 형상은 임의의 방향으로 위치한 유리섬유를 중량비로 30% 함유한 폴리프로필렌 재료가 사용되었고, 시험된 형상은 판재의 굽힘성이나 인장성을 측정하는데 널리 사용되는 스위프트컵(Swift flat-bottomed cup)모양이다. 성형시험과 재료시험은 플리프로필렌 Matrix의 유리성 천이온도(Glass transition temperature)와 용융온도 사이에서 행해졌다. 본 연구의 이론과 고찰을 위해서 재료의 평면 방향으로는 동질성을 그리고 그 직각 방향으로는 이질성을 가진 연속체 물질로 가정하여 유도하였다. 이러한 이론적 결과는 실험 결과와 비교되어졌고,이를 통해 시험된 재료의 최적의 성형조건을 제시하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.202-205
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• 2003

Investigated whether fiber orientation situation of fiber reinforcement macromolecule composition board and the fiber inclusion rate are perpendicular and horizontal direction tensile strength and some correlation. Fiber orientation situation of tensile strength of 0 direction of composition board increased changelessly by aeolotropy in isotropy. Tensile strength of 90 direction that is isotropy and tensile strength of 0 direction that is aeolotropy agreed almost. Get into aeolotropy, the reinforcement rate of fiber decreased. When load interacts for width direction of reinforcement.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.311-315
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• 1998

고분자 재료의 섬유 배향 상태는 각종 물성치의 지표가 되는 가장 기본적인 인자이므로 섬유 배향각 분포의 측진법을 확립하여 섬유 배향 상태를 밝혀두는 것은 재료 설계, 성형조건의 결정, 성형품의 역학적 특성 둥을 예측하는데 있어서 매우 중요하다. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.115-119
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• 1992

산업의 발전과 더불어 새로운 재료의 개발에 대한 요구가 날로 증가하고 있으며 이와 같은 요구에 부응하기위하여 각종의 신소재가 개발되고있다. 이들 신소재 중에서 섬유강화 복합재료는 높은 비탄성과 비강도특성 때문에 구조물의 경량화가 요구되는 우주선, 항공기 등에 주로 이용 되어 왔으며 최근에는 복합재료의 가격이 저렴해 지면서 이 재료의 높은 비탄성과 감쇠특성을 이용하고자 스포츠용품 및 기계 부품에도 섬유강화 복합재료의 이용이 증가 되고 있다. 항공기나 고속회전체의 부품을 복합재료로 제작하였을 경우 복합재료를 다른 금속이나 다른 복합재료부품에 접합(joining)시켜야 하는데 이 때문에구조물의 효율은 Joint에서 주로 죄우된다. Joint를 제작하기 위해서는 복합재료의 표면을 가공한 수 Adhesive를 이용하거나 Bolt로 체결하기 위해 구멍 뚫기 작업이 필요하여 드릴링을 하였을때 이 재료가 매우 연마성이 강하여 심한 공구마멸을 일으키며, 드릴의 입구와 출구쪽에서 각 ply들의 박리 현상이 발생하고, 드릴가공된 벽면으로부터 섬유 또는 레진의 탈락현상등이 발생하는 결점을 가지고 있다. 따라서 본 연구에서는 이러한 결점을 최소화하여 고정밀도의 높은 생산성을 얻기위한 가공기술에 대한 자료를 만들고 최적 절삭조건 및 복합재료가공용 드릴의 설계를 위한 지침을 제시하고자 고속도강 표준드릴을 사용하여 유리섬유 에폭시 복합재료및 탄소섬유 에폭시 복합재료의 드릴링 실험에서 절삭조건이 가공면 생성, 공구마멸, 절삭력에 미치는 영향에 대하여 조사하였다.