• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.36-42
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• 2019

In this study, the pre-treatment of lyocell fabrics was performed using phosphoric acid (PA) as a phosphorus flame retardant and melamine resin (MR) as a cross-linking agent to fabricate carbon fabrics using lyocell fibers. The physical and chemical changes were investigated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and weight analysis. We confirmed that the weight yield of the carbon fabrics compared to the untreated fabrics increased by 14.7%, and width and length yield of the fabrics increased by 15% and 15.5%, respectively. This may be due to the effect of promoting the dehydration reaction of cellulose, forming char on the fiber surface, which induces a crosslinking reaction in the cellulose molecule and stabilizes the structure upon pyrolysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.497-505
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• 1992

본 연구에서는 최근에 개발된 직물 탄소섬유강화 복합재료의 파괴인성치를 정 량적으로 결정하고 파괴거동을 조사하고자 한다. 본 연구의 목적은 이 재료에 선형 탄성파괴역학의 적용여부를 알아보고, R곡선을 이용하여 균열의 생성점 및 불안정 파 괴점의 파괴인성치를 정확히 구하며, 주사형 전자현미경을 통해 파단면 및 균열 성장 시점을 관찰하여 파괴거동을 조사하는데 있다.

• Journal of Adhesion and Interface
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• v.14 no.3
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• pp.146-159
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• 2013

In the present study, stabilized rayon fabrics were prepared from fast isothermal stabilization processes, which were carried out within four minutes at $350^{\circ}C$. The effects of ultrasonic cleaning and chemical pre-treatment on the chemical composition, physical characteristics, X-ray diffraction pattern, thermal stability and shape of the stabilized rayon fabrics were investigated extensively. In order to reduce the weight loss and thermal shrinkage of rayon fabrics occurring during the stabilization process, ultrasonic cleaning was first conducted and then chemical pre-treatments using $NH_4Cl$, $Na_3PO_4$, $H_3PO_4$, and $ZnCl_2$ were performed, respectively. The results indicated that both ultrasonic cleaning and chemical pre-treatment influenced the weight loss, thermal shrinkage, microstructure, carbon content, thermal stability and fabric shape of stabilized rayon fabrics. Also the results depended on the fast-stabilization time and the type of chemical pre-treatment agents used.

• Composites Research
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• v.19 no.3
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• pp.1-6
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• 2006

As the structures of the high performance electronic equipments and devices recently become more complex, the electromagnetic interference (EMI) and compatibility (EMC) have been very essential for commercial and military purposes. Thus, sensitive electrical devices and densely packed systems need to be protected from electromagnetic wave. In this research, glass fabric/epoxy composites containing conductive multi-walled carbon nanotube (MWNT) and carbon fiber/epoxy composites as electrical shielding materials were fabricated and electrical properties of the composites were measured. The concerning frequency band is from 300 MHz to 1 GHz. The performances of composite shielding enclosures were predicted using electromagnetic wave 3-D simulation tool, CST Microwave Studio. The shielding enclosure made of carbon fiber/epoxy composites were fabricated and the shielding effectiveness (SE) was measured in the anechoic chamber.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.375-382
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• 2016

The mechanical property of a carbon-fiber-reinforced plastic (CFRP) is subjected to two elements, carbon fiber and polymer resin, in a first step and the selection of multi-layered structure is second one. Many combination of fabric layers, i.e. plainweave, twillweave, can be derived for candidates of test specimen used for a basic mechanical components so that a reliable identification of dynamic nature of possible multi-layered structures are essential during the development of CFRP based component system. In this paper, three kinds of multi-layered structure specimens were prepared and the dynamic characteristics of service specimens were conducted through classical modal test process with impact hammer. In addition, the design sensitivity analysis based on transmissibility function was applied for the measured response data so that the response sensitivity for each resonance frequency were compared for three CFRP test specimens. Finally, the evaluation of CFRP specimen over different multi-layered fabric structures are commented from the experimental consequences.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.920-928
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• 2006

Fiber-reinforced composites transmitting microwaves of certain frequencies or bands were proposed. These frequency selective fabric composites(FSFCs) are fabricated by weaving carbon fibers and dielectric fibers that build periodic patterns. Design parameters affecting the electromagnetic characteristics of FSFCs were widely discussed, Then the electromagnetic characteristics of a fabricated plain-weave FSEC were investigated with regard to the electrical conductivities of carbon roving, the fiber undulation, and the aperture-to-cell ratio, for the electrical conductivities, its dependence on frequency as well as on the fiber volume fraction of carbon roving was taken into account. Constituent material properties and the fiber undulation had little effect on the EM properties of the fabricated FSFC, while the aperture-to-cell ratio made a profound effect on them.

• Science of Emotion and Sensibility
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• v.24 no.4
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• pp.129-138
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• 2021

This study aimed to determine the effects of the shape and attachment position of stretchable textile sensors coated with carbon nanotube on their performance when used to measure children's joint movements. Moreover, the child-safe requirements for fabric motion sensors are established. The child participants were advised to wear integrated clothing equipped with the sensors of various shapes (rectangular and boat-shaped) and attachment positions (at the knee and elbow joints or 4 cm below the joints). The voltage change induced by the elongation and contraction of the fabric sensors was determined for arm and leg flexion-extension motions at 60 deg/s (three measurements of 10 repeats each for 60°and 90°angles, for a total of 60 repetitions). Their dependability was determined by comparing the fabric motion sensors to the associated acceleration sensors. The experimental results indicate that the rectangular-shaped sensor affixed 4 cm below the joint is the most effective fabric motion sensor for measuring children's arm and leg motions. In this study, we designed a textile sensor capable of tracking children's joint motion and analyzed the sensor shape and attachment position on motion sensing clothing. We demonstrated that flexible fabric sensors integrated into garments may be used to detect the joint motions of the human body.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.185-188
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• 2007

The main objective of this research effort was to develope the performance of C/SiC composites manufactured by LSI (Liquid Silicon Infiltration) method for solid and liquid rocket propulsion system and ensure the performance analysis technique. The various carbon preform were manufactured by filament winding, tape rolling, involute layup and stack molding process. For the best performance of thermal and mechanical properties, many process conditions were tested and selected by varying preform, the content of SiC, temperature, impregnation resin and chemical vapour reaction. In conclusion, the high performance and reliability of C/SiC composite were proved for solid and liquid rocket propulsion system. And the performance analysis technique related to mathematical ablation model was originated.

• Science of Emotion and Sensibility
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• v.18 no.4
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• pp.25-34
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• 2015

TThis study explored the requirement of fabric sensor that can measure the motion of the joint effectively by measuring and analyzing the variation in electric resistance of a sensor in accordance with bending and stretching motion of the arm by the implementation of a motion sensor utilizing conductive fabric. For this purpose, on both sides of two kinds of knitted fabric, namely 'L' fabric and 'W' fabric Single Wall Carbon Nano-Tube(SWCNT) was coated, fabric sensor was developed by finishing them in a variety of ways, and the sensor was attached to the arm band. The fabric sensor consisted of total 48 cases, namely background fabric for coating, the method of sensor attachment, the number of layer of sensors, the length of sensor, and the width of sensor. The performance of fabric motion sensors in terms of a dummy arm, that is, a Con-Trex MJ with 48 arm bands around it was evaluated. For each arm band, a total of 48, fastened around the dummy arm, it was adjusted to repeat the bending and stretching at the frequency : 0.5Hz, ROM : $20^{\circ}{\sim}120^{\circ}$, the voltage was recorded for each case after conducting three sets of repeat measurement for a total of 48 cases. As a result of the experiment, and as a consequences of the evaluation and analysis of the voltage based on the uniformity of the base line of the peak-to-peak voltage(Vp-p), the uniformity of Vp-p within the same set, and the uniformity of the Vp-p among three sets, the fabric sensors that have been configured in SWCNT coated 'L' fabric / welding / two layers / $50{\times}5mm$, $50{\times}10mm$, $100{\times}10mm$, and SWCNT coated 'W' fabric / welding / two layers / $50{\times}10mm$ exhibited the most uniform and stable signal value within 5% of the total variation rate. Through all these results of the experiment, it was confirmed that SWCNT coated fabric was suitable for a sensor that can measure the human limb operation when it was implemented as a fabric sensor in a variety of forms, and the optimal sensor types were identified.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.719-724
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• 2009

In this study, DCB(double cantilever beam) specimens of woven fabric carbon/epoxy and glass/epoxy were manufactured and mode I fracture toughness of specimen was measured according to ASTM 5528-01. And FE analysis was conducted in the same condition and evaluated the behavior of delamination analytically. Mode I fracture toughness measured by test was $845.7\;J/m^2$ in the case carbon/epoxy and that of glass/epoxy was $1,042\;J/m^2$. FE analysis was conducted using cohesive elements for adhesive layer and applied measured fracture toughness. To verify the result of analysis, the reaction force measured at the end of specimen and that calculated by Timoshenko beam theory were compared. The numerical results show good agreements with the measured one.