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Volume 26 (2000)
- Issue 6 Pages 203-
- Issue 5 Pages 163-
- Issue 4 Pages 121-
- Issue 3 Pages 83-
- Issue 2 Pages 37-
- Issue 1 Pages 1-
Volume 26, Issue 4
Displaying 1-3 of 3 articles from this issue
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Hiroshi TSUDA, Shin-ichi TAKEDA, Kei URABE, Jun TAKAHASHI, Teruo KISHI2000 Volume 26 Issue 4 Pages 121-129
Published: July 15, 2000
Released on J-STAGE: August 11, 2009
JOURNAL FREE ACCESSResponse of a Michelson Interferometric fiber-optic sensor to impact loading was investigated. A Michelson Interferometric fiber-optic sensor was mounted on the surface of unidirectionally aligned carbon fiber-reinforced epoxy composites. Using a Charpy tester, the load was applied to the specimen at two impact energy levels. One was the case where the specimen sustained no damage; another was the case where localized damage occurred in the specimen. Both the optical interference signal and the strain were measured during the impact loadings. The spectrum analysis of the interference signal was performed by the Fast Fourier Transforms. The analytical results were compared with the predicted frequency characteristics from the strain rate. In the case where damage occurred in the specimen, the interference signal recorded before and after the peak in load and during unloading had relatively high intensity in wider frequency range than that predicted from the strain rate. This discrepancy in frequency characteristics is attributed to the vibration induced by fiber breaking or crack closure. The Michelson interferometric fiber-optic sensor proved to be effective for detecting the impact damage of the material studied.View full abstractDownload PDF (7910K) -
Kazumasa MORIYA, Shinichiro NISHIYAMA, Hiroyuki MOTOYAMA2000 Volume 26 Issue 4 Pages 130-140
Published: July 15, 2000
Released on J-STAGE: August 11, 2009
JOURNAL FREE ACCESSExperimental tests have been conducted on the mechanical behavior of a CFRP 1×7 strand cable with a central core subjected to torsional loading. The failure process of each helical string and the core has been probed independently by means of an electrical resistance method. Unloadingreloading torsion test has also been done to investigate the effects of cyclic loading. It has been found that the torsional failure of the CFRP strand cable has two stages. The first is a compressive failure of core, which does not immediately result in a loss of load-carrying capacity, but it later induces a tensile fracture of all spiral strings, i.e. the final failure of the cable. Although the tensile strength of the CFRP strand cable is almost the same as that of the steel strand cable of the same diameter, its torsional properties are far lower than those of the steel cable. Cyclic loading causes more damage to the core than to the spiral strings and it reduces the torsional strength significantly. The electrical resistance method, which requires no external sensor, works successfully for the sensitive detection of the fiber breakage in core and spiral strings and hence, the present CFRP strand cable can be regarded as a smart structural element with health-monitoring capability.View full abstractDownload PDF (3004K) -
Takashi ISHIKAWA, Masamichi MATSUSHIMA, Yoichi HAYASHI2000 Volume 26 Issue 4 Pages 141-151
Published: July 15, 2000
Released on J-STAGE: August 11, 2009
JOURNAL FREE ACCESSExtensive experimental research was conducted to pursue mechanical behavior occurred in the actual Compression-after-Impact (CAI) tests for conventional (brittle) CF/Epoxy composite plates. Two test methods, SACMA and NASA were used and examined for future possible improvements. Comparison of experimental results obtained by the two methods is another key issue in the present paper. Focuses are placed on the pursuit of mechanism of behavior during the tests. By examining the mechanics, an appropriate parameter was discovered for unified data reduction obtained by the two methods. It is based on a ratio of a virtual cylinder with an effective diameter of delamination excluding the “brim” region to a total sectional area of the specimen. CAI strengths and initial local buckling in delaminated area were universally explained by this parameter.View full abstractDownload PDF (8297K)
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