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1,087 results on '"Takeda, Nobuo"'

156. Evaluation of the influence of cooling rate on residual strain development in unidirectional carbon fibre/polyphenylenesulfide laminates using embedded fibre Bragg grating sensors.

Author

Tsukada, Takuhei, Takeda, Shin-ichi, Minakuchi, Shu, Iwahori, Yutaka, and Takeda, Nobuo

Subjects
STRAINS & stresses (Mechanics), CARBON fibers, LAMINATED materials, FIBER Bragg gratings, THERMOPLASTIC composites, THERMAL properties
Abstract

This study investigates the influence of cooling rate on the residual strain of the carbon fibre/polyphenylenesulfide unidirectional laminates. Three different cooling rates (−300℃/min, −100℃/min and −10℃/min) were applied to simulate a wide range of cooling conditions. The crystallisation behaviour which depends on the cooling rate was evaluated using differential scanning calorimetry. A process monitoring test was then conducted using embedded fibre Bragg grating sensors. In-plane transverse strain of carbon fibre/polyphenylenesulfide unidirectional laminates was measured and the results were presented based on the crystallisation behaviour determined by differential scanning calorimetry. Furthermore, residual strain change after subsequent annealing was examined. This study successfully demonstrates the effectiveness of in situ process monitoring using fibre Bragg grating sensors for evaluating material behaviour of thermoplastic composites during rapid heating and cooling under realistic processing conditions. [ABSTRACT FROM AUTHOR]

Published
2017
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157. Process improvement for out-of-autoclave prepreg curing supported by in-situ strain monitoring.

Author

Takagaki, Kazunori, Hisada, Shinsaku, Minakuchi, Shu, and Takeda, Nobuo

Subjects
AUTOCLAVES, BOILERS, SANITATION equipment, PRESSURE vessels, OPTICAL fiber detectors
Abstract

Vacuum-bag-only curing is an attractive out-of-autoclave method as an alternative to conventional autoclave curing. Previous extensive researches provided great insight into void formation during the vacuum-bag-only method and these findings are reflected in current vacuum-bag-only cure cycles to minimize void content. Cure process can be further improved by taking into consideration cure-induced residual stress/strain. The present paper proposed a residual stress/strain reduction method and evaluated its effectiveness using a commercially available vacuum-bag-only material by fiber-optic-based in-situ strain monitoring and tensile tests. First, cure process monitoring and tensile tests were conducted for the manufacturer’s recommended cure cycle. Cure process monitoring showed that the material vitrifies during post-cure temperature dwell. Furthermore, the tensile test revealed that the vacuum-bag-only material has lower strength than conventional autoclave materials, suggesting the importance of the effect of cure-induced residual stress/strain. Then, two cure cycles were proposed based on the findings from the manufacturer’s recommended cure cycle tests and a cure kinetics model. In the proposed cycles, resin vitrifies at a lower temperature than the manufacturer’s recommended cure cycle, leading to reduced residual stress/strain. Cure process monitoring and tensile test results for the new cycles showed that the residual strain was reduced by 12–18%, and the strength was increased by 26% in the best case. Moreover, void content was not significantly affected by changing the cure cycle. Although vacuum-bag-only material was used in this research, the proposed concept can be widely applied for autoclave cures and other types of vacuum-bag-only processes with slight modification. [ABSTRACT FROM AUTHOR]

Published
2017
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163. Detection of Trace Water Vapor Using SiOx-Coated Ball SAW Sensor

Author

Takayanagi, Kosuke, primary, Akao, Shingo, additional, Yanagisawa, Takayuki, additional, Nakaso, Noritaka, additional, Tsukahara, Yusuke, additional, Hagihara, Satoshi, additional, Oizumi, Toru, additional, Takeda, Nobuo, additional, Tsuji, Toshihiro, additional, and Yamanaka, Kazushi, additional

Published
2014
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174. Evaluation of damage detectability in practical sandwich structure application conditions using distributed fiber optic sensor.

Author

Siivola, Juho T., Minakuchi, Shu, Mizutani, Tadahito, and Takeda, Nobuo

Subjects
OPTICAL fiber detectors, OPTICAL fiber communication, INTEGRATED optics, PHOTONICS, OPTOELECTRONIC devices
Abstract

Indentation loading or low-velocity impacts on foam core sandwich structures can leave only barely visible damage on the face sheets while causing notable damage in the core due to the thin face sheets and relatively weak core. In practical applications, the measurement and damage detection can also be notably affected by environmental conditions and relaxation of the foam core. To detect the damages, a Rayleigh-scattering-based fiber optic strain monitoring system with high spatial resolution was applied to foam core sandwich structures. Damage detection ability of the system was therefore tested by indentation tests on sandwich beam and panel specimens while also considering the aforementioned effects. Finite element analysis verified by the measurements was used to provide a method to estimate the damaged core area from the measured strain data. Finally, the monitoring ability of the system was demonstrated by low-velocity impact tests on a large scale sandwich panel. The used system provided detailed strain data during and after indentation and impact tests. Due to the high resolution of the system, the damage location and size could be estimated from the obtained strain data even when barely visible dent remained on the face sheet, thus demonstrating the damage detection ability even at various environmental conditions and after relaxation of the foam core. [ABSTRACT FROM AUTHOR]

Published
2016
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