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Design of Radar Absorbing Structures Utilizing Carbon-Based Polymer Composites
Kim, Sang-Young,Kim, Sung-Soo RAPRA 2018 POLYMERS AND POLYMER COMPOSITES Vol.26 No.1
<P>Radar absorbing structure (RAS) is a composite laminate with a low reflection coefficient for the electromagnetic illumination in microwave frequency range, and thereby can be used in the stealth technology and electromagnetic compatibility (EMC). In this study, microwave absorbing properties of a two-layer composite laminate (carbon black impregnated rubber sheet attached to the carbon fiber epoxy composite panel) has been investigated. Complex permittivity and permeability of the composite materials were measured in C- and X-band frequencies (4-12 GHz) by reflection/transmission technique using a coaxial waveguide and network analyzer. Complex permittivity can be controlled with the amount of carbon black in the rubber composite. High values of dielectric constant and dielectric loss are observed in the carbon fiber composite. Optimization of microwave absorption is conducted for the two-layer RAS on the basis of transmission line theory. It is found that microwave absorption is strongly sensitive to carbon black content in the rubber composite and its layer thickness. For the rubber sheet containing 10% carbon black (with dielectric constant the maximum microwave absorption (30 dB) is predicted at 10 GHz.</P>
Evaluation of Pp/Clay Composites as Soundproofing Material
Yan, Jun,Kim, Myung-Sub,Kang, Kyung-Min,Joo, Kyung-Hoon,Kang, Yeon-June,Ahn, Sung-Hoon RAPRA 2014 POLYMERS AND POLYMER COMPOSITES Vol.22 No.1
Noise should be disappeared or reduced by using soundproofing materials in our daily life. Polypropylene (PP)/Clay composites are interesting because of their physical and mechanical properties dramatically increased by small quantity of clay filled in PP matrix. In this paper, different types of specimens were made at 0.9, 2.9, 4.8, 6.5, 8.2 and 9.9 wt.% of organically modified clay reinforced PP (100 gram) by solvent based techniques. A heating press and laser cutting process were used to create specimens with thickness 3 mm, diameter 29 mm and 100 mm for high and low sound frequency test, respectively. The soundproofing property was measured by sound transmission loss (TL) through impedance tube method. The measured results showed that about 7 similar to 14.8 dB sound TL was increased for 29 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 3200 similar to 6400Hz. And about 3.3 similar to 5.3 dB sound TL was increased for 100 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 520 similar to 640Hz. In addition, mechanical properties of this composite were measured, and TEM images were taken in order to observe the micro-structure for research on relationship between soundproofing property and micromechanism.
Park, J.S.,Kim, S.B.,Kim, H.R.,Nam, B.U. RAPRA 2014 POLYMERS AND POLYMER COMPOSITES Vol.22 No.2
Poly(ethylene-co-isosorbide terephthalate)(PEIT)/multi-walled carbon nanotube (MWCNT)/ethylene terpolymer composites were prepared by a melt mixing process. The effects of MWCNT and the ethylene terpolymer of nanocomposites on the mechanical, thermal and electrical properties were investigated. MWCNT and ethylene terpolymer from 1 to 5 phr and 5 wt.% and 10 wt.% were added to the PEIT matrix, respectively. The thermal properties were evaluated by DSC and TGA. The morphology, mechanical properties and electrical characteristics were assessed by FE-SEM, a notched Izod impact strength tester and a surface resistance meter. As a result, we found that the PEIT/MWCNT/ethylene terpolymer composites have higher conductivity and better mechanical properties than neat PEIT resin.
Chung, Yong-Chan,Kim, Ho-Sung,Chun, Byoung Chul RAPRA 2018 POLYMERS AND POLYMER COMPOSITES Vol.26 No.2
<P>Reduced graphene oxide (RGO) or graphite is functionalized with hydroxyl groups for linking to the sides of polyurethane (PU) chains. Blended PU with RGO or graphite is prepared as a control for comparison. The PU composites are compared with respect to their spectroscopic, thermal, mechanical, shape memory, and sheet resistance properties. Scanning electron microscopy images demonstrate the good distribution of functionalized graphene oxide (FGO) or functionalized graphite (FG) particles on the inner surface of the PU. The linking of FGO or FG onto PU does not significantly affect the thermal behavior or shape memory properties but sharply improves the tensile strength of the PU composites without a noticeable decrease in tensile strain. The shape recovery of PU composites remains at approximately 90%, regardless of the FGO or FG content. The FG-linked PU composites exhibit a sharp decrease in sheet resistance as the FG content increases, whereas the sheet resistance of the FGO-linked PU composites does not decrease with increasing FGO content. The control PU composites with blended RGO or graphite show significant reductions in their sheet resistance. Considering the ease of functionalization of the graphite surface and the significant improvement in tensile strength, linking FG onto PU is advantageous for the development of PU composites with low sheet resistance.</P>