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Volume 38 (2012)
- Issue 6 Pages 228-
- Issue 5 Pages 183-
- Issue 4 Pages 137-
- Issue 3 Pages 93-
- Issue 2 Pages 41-
- Issue 1 Pages 8-
Volume 38, Issue 2
Displaying 1-3 of 3 articles from this issue
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Research paper
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Masahito UEDA, Tomoyuki YAMAGUCHI, Teppei OHNO, Yasuyuki KATO, Tetsu N ...2012 Volume 38 Issue 2 Pages 41-50
Published: 2012
Released on J-STAGE: December 10, 2012
JOURNAL FREE ACCESSCarbon fiber reinforced plastic (CFRP) has electrical conductivity both in parallel and transverse direction of fiber. Since the electrical network may be changed with applied strain, the electrical conductivity of the CFRP would also be changed for the piezoresistivity. Strain monitoring of CFRP, therefore, can be performed without any additional sensor but by measuring the electrical resistance change. There has been many studies on the gage factors of unidirectional CFRPs, although significant mutual differences were found out in the results reported. It is considered that the differences may be caused by the strong electrical anisotropy and inhomogenity of the unidirectional CFRP. In this study, a new concept was introduced to measure the gage factors of a unidirectional CFRP precisely. Finite element analysis was utilized to take into considered non-uniform electrical potential field in the unidirectional CFRP. The gage factors were obtained as a result of minimizing the error sum of squares of electrical potentials between experimental and analytical results. Gage factor in fiber direction was affected by that in thickness direction depending on the specimen configuration. FEM analysis showed the possibility that the unidirectional CFRP may show both positive and negative gage factor in fiber direction.View full abstractDownload PDF (2480K) -
Satoshi KOBAYASHI, Atsushi TANAKA2012 Volume 38 Issue 2 Pages 51-57
Published: 2012
Released on J-STAGE: December 10, 2012
JOURNAL FREE ACCESSIn order to fabricate composite components rapidly, a micro-braiding technique have been proposed and investigated. In the present study, a simple model is proposed to predict the resin impregnation process based on the Darcy's law and the continuity equation. Bending modulus was also modeled considering the difference between tensile and compressive moduli of a carbon fiber and resin impregnation. To confirm validity of the models, carbon fiber reinforced polypropylene composites were molded under various molding conditions. Cross-sectional observation results indicated the model proposed was possible to predict resin impregnation. Four-points bending tests were also conducted on the composites. It is confirmed that bending moduli were well-predicted based on the proposed model.View full abstractDownload PDF (1996K) -
—Dynamic Detection of Impact Damages and Recovery of Mechanical Properties—Yoji OKABE2012 Volume 38 Issue 2 Pages 58-66
Published: 2012
Released on J-STAGE: December 10, 2012
JOURNAL FREE ACCESSIn this research, fiber Bragg grating (FBG) sensors that were a kind of optical fiber sensors and shape memory alloys (SMA) were incorporated into honeycomb sandwich structures for development of smart panels with damage detection and shape recovery functions. Especially, in this paper, impact damages in honeycomb sandwich panels with CFRP skins were targeted. A MEMS optical spectrum analyzer that can measure the reflection spectrum of an FBG sensor at high speed was introduced. Then, the difference in the size and location of impact damage in the sandwich panel was detected from the difference of deformation process in the reflection spectrum during the impact loading. On the other hand, the impact damage was attempted to be repaired by manufacturing of the honeycomb core from SMA foils. As a result, the typical mechanical properties, such as the bending stiffness and the in-plane compressive strength, were confirmed to be recovered along with the shape recovery of the sandwich panel by heating.View full abstractDownload PDF (2974K)
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