• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.4
• /
• pp.328-338
• /
• 2007

One of main advantages of composite using smart material as reinforcement can be controlled cracks behavior inside the composite. If the smart composite is applied as part of the structure, the use of the shape memory effect of the smart material is the best way to protect the propagation of cracks generated in the structure while use. In this study, the optical manufacturing conditions for the smart composite were derived. In order to evaluate the shape memory effect by shape memory alloy, the tensile load was applied to the smart composite and stress distribution was inspected. And then, the smart composite was heated to a certain temperature and the shape memory alloy would shrink to the original shape. Finally, at this point the recovering status of stress using photoelastic instrument was discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.11a
• /
• pp.130-132
• /
• 2018

등부표는 항로를 가리키는 표지의 한 가지로써 암초나 얕은 곳 따위를 알리는 중요한 역할을 한다. 본 연구에서는 LED 등부표의 경량화, 내부식성, 높은 기계적 물성확보를 위해 탄소섬유/에폭시 복합재료를 적용하였다. 더불어, 자가발전이 가능한 스마트 LED 등부표 개발을 위해 전기활성고분자 필름을 적용하여 가능성을 확인하였다.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.04a
• /
• pp.209-212
• /
• 1999

• Composites Research
• /
• v.34 no.6
• /
• pp.400-405
• /
• 2021

In this study, a composite material frame was designed to increase the energy harvesting efficiency of polyvinylidene fluoride (PVDF) ribbon harvesters which are installed inside smart shoes. In order to minimize the amount of deformation in the load direction of the frame, it was designed using carbon continuous fiber composites and its complex shaped structure was manufactured using a 3D printer. In order to calculate the amount of deformation of the insole and midsole of the shoes under the condition of the load generated during walking, the insole and midsole were modeled using the distributed spring elements. Using finite element analysis, the elongation of ribbon-type harvesters mounted on smart shoes was calculated during walking. It is expected that the predicted elongation of the harvester can be utilized to increase the energy harvesting efficiency of smart shoes.

• Composites Research
• /
• v.29 no.6
• /
• pp.379-387
• /
• 2016

Structural model of laminated composite plate based on the first order shear deformation theory and subjected to a combination of piezoelectric, electromagnetic and thermal fields is established. Coupled equations of motion are derived via Hamilton's principle on the basis of electromagnetic and piezoelectric equations which are involved in constitutive equations. Proportional control and velocity feedback control logics are applied via boundary control moments and forces. Variations of dynamic chasracteristics of composite plate with collocated piezoelectric sensor and actuators, electromagnetic field and temperature gradient are investigated and it reveals that dynamic characteristics of structure can be effectively controlled by utilizing the piezoelectric effect and ply angles of fiber reinforced composites.

• Composites Research
• /
• v.28 no.4
• /
• pp.155-161
• /
• 2015

A composite structure was fabricated with embedded impact detection capabilities for applications in Structural Health Monitoring (SHM). By embedding sensor functionality in the composite, the structure can successfully perform impact localization in real time. Smart resin, composed of $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,\;Ti)O_2$ (PNN-PZT) powder and epoxy resin with 1:30 wt%, was used instead of conventional epoxy resin in order to activate the sensor function in the composite structure. The embedded impact sensor in the composite was fabricated using Hand Lay-up and Vacuum Assisted Resin Transfer Molding(VARTM) methods to inject the smart resin into the glass-fiber fabric. The electrodes were fabricated using silver paste on both the upper and bottom sides of the specimen, then poling treatment was conducted to activate the sensor function using a high voltage amplifier at 4 kV/mm for 30 min at room temperature. The composite's piezoelectric sensitivity was measured to be 35.13 mV/N by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. Because impact sensor functionality was successfully embedded in the composite structure, various applications of this technique in the SHM industry are anticipated. In particular, impact localization on large-scale composite structures with complex geometries is feasible using this composite embedded impact sensor.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.316-317
• /
• 2015

무전해 도금은 금속이온을 수용액 상태에서 석출시키는 방법으로서 전기를 사용하지 않고 환원제의 자기촉매 방법에 의해 금속을 도금하는 방법이다. 두께를 확보하기 위한 화학적 무전해 도금에서는 환원제를 사용하지만 선택적 도금에서는 환원제를 사용하지 않는 치환도금법이 주로 사용되고 있다. 최근 전자파 차폐, 포장기술의 응용이 확대되면서 정보 통신 스마트폰, 전자기술과 자동차 산업에 많은 고분자 복합도금이 널리 확대되고 있다. 최근 해외에서도 고분자와 비금속재료의 복합도금 기술이 관심을 끌고 있다. 2013년 중국의 J. B. Fei 등은 Ag나노체인 합성물에 필요한 비대칭형의 공유결합으로써 나선형의 자기배열 $AgNO_3$와 멜라민 특성을 보고하였다. 무전해 니켈 복합도금은 내마모성, 내식성과 비금속재료의 선택적인 첨가로 다양한 고분자 첨가물을 적용할 수 있다. 유전상수가 낮고 열적 안정성이 우수하여 노트북 컴퓨터나 스마트폰 표면에 니켈-폴리이미드 복합도금도 개발되고 있다.

• Composites Research
• /
• v.20 no.3
• /
• pp.37-42
• /
• 2007

Tensile residual stress is occurred by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite with occurring of compressive residual stress in the matrix by its shape memory effect. A hot press method was used to create the optimal fabrication condition for a Shape Memory Alloy(SMA) composite. The bonding effect of the matrix and the reinforcement within the SMA composite by the hot press method was strengthened by cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/A16061 shape memory alloy composite at low temperature. The damage degree for the specimen that underwent thermal shock cycles was also discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.2
• /
• pp.59-66
• /
• 2002

In this paper, we present the simulataneous monitoring of the strain and temperature during cures f various composite laminates using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors. Three types of graphite/epoxy composite were used : a undirectional laminate, a symmetric cross-ply laminate, and a fabric laminate. Two FBG/EFPI hybrid sensors were embedded in each laminate at different directions and different locations. We performed the real time monitoring of fabrication strains and temperatures at two points within the composite laminates during cure process in an autoclave. Throuhg these experiments, FBG/EFPI sensors proved to be an efficient choice for smart cure monitoring of composite structures.

• Composites Research
• /
• v.16 no.1
• /
• pp.34-41
• /
• 2003

A cure process control model was proposed to optimize the curing process of thick filament wound structure. There are two types of smart cure, one is that the boundary conditions of the hollow cylinder are same between inner surface and outer surface, and the other is that inner surface temperature is slightly higher than outer surface to initiate cure reaction from the inner side to the outer side to reduce residual stress.