• Proceedings of the KSME Conference
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• 2004.04a
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• pp.192-197
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• 2004

The anisotropy in coefficient of thermal expansion (CTE) between the in-plane and out-of-plane of 3-dimensional thick composite structures induces residual stresses and the large void content due to insufficient compaction of fabric composites, which results in low interlaminar strengths. In order to reduce the through thickness CTE and the void content, in this work, carbon fabric phenolic laminates were compacted by pressure generated by autoclave and a compressive jig, from which the through-thickness CTEs and the void contents were measured. From the measurement, it was found that the through-thickness CTE and the void content had different characteristics from ordinary composites due to gas produced during the cure reaction of phenolic resin.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.74-78
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• 2001

In this study, out-of-plane properties and CTEs were predicted for 8-harness satin weave textile composites. The properties were calculated by unit cell analysis for configurations with varied waviness ratio and phase shifts. Macro elements were employed to reduce the computer resource requirement. It was found that the out-of-plane properties and CTEs were varied as the phase shift changed. However the dependency was much weaker than the in-plane properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2407-2414
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• 2015

This paper presents analytical expressions for the determination of out of plane thermo-elastic properties for conventional laminated composite plates. The approach follows that commonly accepted for in-plane properties. Results over a variety of lay-ups reveals that it is poor assumption to use transverse tape lamina properties to represent out of plane laminate properties for laminates with more than 10% plies oriented off-axis($90^{\circ}$) from uniaxial or for laminates with angle plies of $15^{\circ}$ or greater.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.263-267
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• 2006

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a significant deflection with relatively small temperature rise. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. Additionally, we can achieve response time of 14.6 ms, resonance frequency of 12 Hz, and reliability ability of $10^5$ cycles. The proposed actuator can find applications where a large vertical displacement is needed while maintaining compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1286-1289
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• 2004

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene(PVDF-TrFE). The large difference of coefficient of thermal expansion(CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a large deflection with relatively small temperature rising. Compared to the most conventional micro actuators based on MEMS(micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. The proposed actuator can find applications where a large vertical displacement is needed while keeping compact overall device size, such as a micro zooming lens.

• Carbon letters
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• v.22
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• pp.25-35
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• 2017

The aim of the work was to investigate the thermo-electrical properties of low cost and rapidly produced randomly oriented carbon/carbon (C/C) composite. The composite body was fabricated by combining the high-pressure hot-pressing (HP) method with the low-pressure impregnation thermosetting carbonization (ITC) method. After the ITC method step selected samples were graphitized at $3000^{\circ}C$. Detailed characterization of the samples' physical properties and thermal properties, including thermal diffusivity, thermal conductivity, specific heat and coefficient of thermal expansion, was carried out. Additionally, direct current (DC) electrical conductivity in both the in-plane and through-plane directions was evaluated. The results indicated that after graphitization the specimens had excellent carbon purity (99.9 %) as compared to that after carbonization (98.1). The results further showed an increasing trend in thermal conductivity with temperature for the carbonized samples and a decreasing trend in thermal conductivity with temperature for graphitized samples. The influence of the thickness of the test specimen on the thermal conductivity was found to be negligible. Further, all of the specimens after graphitization displayed an enormous increase in electrical conductivity (from 190 to 565 and 595 to 1180 S/cm in the through-plane and in-plane directions, respectively).