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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Korean Society for Composite Materials
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Volume & Issues
Volume 20, Issue 6 - Dec 2007
Volume 20, Issue 5 - Oct 2007
Volume 20, Issue 4 - Aug 2007
Volume 20, Issue 3 - Jun 2007
Volume 20, Issue 2 - Apr 2007
Volume 20, Issue 1 - Feb 2007
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Study on Mechanical and Electrical Properties of Expanded Graphite/Carbon fiber hybrid Conductive Polymer Composites
Oh, Kyung-Seok ; Heo, Seong-Il ; Yun, Jin-Chul ; Han, Kyung-Seop ;
Composites Research, volume 20, issue 6, 2007, Pages 1~7
Expanded graphite/carbon fiber hybrid conductive polymer composites were fabricated by the preform molding technique. The conductive fillers were mechanically mixed with a phenol resin to provide an electrical property to composites. The conductive filler loading was fixed at 60wt.% to accomplish a high electrical conductivity. Expanded graphites were excellent in forming a conductive networking by direct contacts between them while it was hard to get the high flexural strength over 40MPa with using only expanded graphite and phenol resin. In this study, carbon fibers were added in composites to compensate the weakened flexural strength. The effect of carbon fibers on the mechanical and electrical properties was examined according to the weight ratio of carbon fiber. As the carbon fiber ratio increased, the flexural strength increased until the carbon fiber ratio of 24wt.%, and then decreased afterward. The electrical conductivity gradually decreased as the increase of the carbon fiber ratio. This was attributed to the non-conducting regions generated among the carbon fibers and the reduction of the direct contact areas between expanded graphites.
Experimental Debonding Failure Behaviors of Composite Skin-Stiffener Bonded Specimens
Kim, Kwang-Soo ; An, Jae-Mo ; Jang, Young-Soon ; Yi, Yeong-Moo ;
Composites Research, volume 20, issue 6, 2007, Pages 8~14
Debonding failure characteristics of the composite skin-stiffener specimens were experimentally investigated. The influences of bonding methods, types of stiffener shape and various secondary bonding parameters were evaluated. Present test results combined with the previous test results showed that the failure displacement of the skin-stiffener specimens well evaluates the skin-stiffener debonding failure strength of the composite stiffened panels. The specimens with an open type stiffener had lower bending stiffness and larger failure displacement than those with a closed type stiffener. Secondary bonding and co-curing with adhesive had better failure strength than co-curing without adhesive film. Secondary bonded specimens failed by adhesive failure and co-cured specimens failed by delamination failure. As the bondline thickness was thinner, the skin-stiffener specimens had higher failure strength. The fillets had no influence on failure strength of the specimens. The influence of the surface roughness was shown according to types of stiffener shape.
Structural Behavior of Thin-Walled, Pretwisted Composite Beams
Park, Il-Ju ; Hong, Dan-Bi ; Jung, Sung-Nam ;
Composites Research, volume 20, issue 6, 2007, Pages 15~20
In this work, the structural response of thin-walled, composite beams with built-in twist angles is analyzed using a mixed beam approach. The analytical model includes the effects of elastic couplings, shell wall thickness, and torsion warping. Reissner's semi-complimentary energy functional is used to describe the beam theory and also to deal with the mixed-nature in the beam kinematics. The bending and torsion related warpings introduced by the non-zero pretwist angles are derived in closed-form through the proposed beam formulation. The theory is validated with available literature and detailed finite element analysis results for rectangular solid section beams with elastic couplings. Very good correlation has been obtained for the cases considered.
Impact Damage Detection in a Composite Stiffened Panel Using Built-in Piezoelectric Active Sensor Arrays
Park, Chan-Yik ; Cho, Chang-Min ;
Composites Research, volume 20, issue 6, 2007, Pages 21~27
Low-velocity impact damage in a composite stiffened panel was detected using built-in piezoelectric active sensor arrays. Using these piezoelectric active sensors, various diagnostic signals were generated to propagate Lamb waves through the structure and the responses were picked up to detect changes in the structure's vibration signature due to the damage. Three algorithms - ADI(Active Damage Interrogation), TD RMS (Time Domain Root Mean Square) and STFT (Short Time Fourier Transform) - were examined to express the features of the signal changes as one damage index. From damage detecting tests, two impact induced delaminations were detected and the location was estimated with the algorithms and diagnostic signals.
Effects of Specimen Size and Testing Velocity on Puncture Properties of Short-fiber Reinforced Chloroprene Rubber
Ryu, Sang-Ryeoul ; Lee, Dong-Joo ;
Composites Research, volume 20, issue 6, 2007, Pages 28~33
The puncture properties of short-fiber reinforced rubber were investigated as functions of fiber aspect ratio(AR: length of fiber/diameter of fiber), fiber content, specimen size and testing velocity. The puncture stresses of the matrix and short-fiber reinforced rubber decreased with specimen size, and increased with testing velocity at same specimen size. As the fiber AR increased the puncture stress at given fiber content also increased. The problem of the specimen shape was investigated by the comparison of the tensile strength with puncture stress. The forces acting in the membrane wall of the matrix and the short-fiber reinforced rubber showed a similar data regardless of specimen size. And those increased with testing velocity at same specimen size. As the fiber AR increased the force acting in the wall at given fiber content also increased. Overall, it was found that the specimen size, testing velocity had an important effects on the puncture properties.