著者

甲嶋 秀平 梶井 憲弘 細井 厚志 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.85, no.871, pp.18-00435, 2019 (Released:2019-03-25)

参考文献数

25

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Carbon fiber reinforced plastics (CFRPs) are widely used as components of marine structures. Thus, it is important to understand the degradation of the mechanical properties and its mechanism under seawater immersion. The object of this study is the influence of seawater immersion on the mechanical properties of plain woven CFRP laminates. Static tensile test and tensile fatigue test were carried out on the CFRP immersed different time under seawater for 300, 2500 and 5400 hours. The mechanical properties immersed for 300 hours was almost the same value compared with those of no immersion. However, the tensile strength immersed for both 2500 and 5400 hours reduced by 22.5% compared with that of no immersion. Then, from the fatigue results, in the low-cycle fatigue region, the fatigue strengths decreased as immersion time was longer, on the other hand, in the high-cycle fatigue region, the fatigue strength did not change significantly regardless of immersion time. As a result, the inclination of S-N curves became gentle as immersion time was longer. From observation of fracture surfaces by scanning electron microscopy (SEM), it was shown that the fiber/matrix interface deteriorated remarkably after seawater immersion. Moreover, the difference of damage growth behaviors due to immersed in seawater under fatigue loading was investigated using soft X-ray photography. On specimen immersed in seawater, the accumulation of damage expanded more widely due to interface degradation compared with that of no immersion. Considering these results, it was suggested that the static tensile strength depended on load transmission efficiency between fiber and matrix, on the other hand, the fatigue strength in high cycle fatigue region depended on the strength of fiber along 0° that had small influences by seawater immersion.

著者

奥茂 洸一 髙橋 祐衣 金 太成 二川 秀史 細井 厚志 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

pp.19-00029, (Released:2019-06-03)

参考文献数

23

被引用文献数

1

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Carbon nanotubes (CNT) have remarkable mechanical properties and low density. Since length of the CNT is limited, CNT yarn is regarded as a reinforced fiber of carbon fiber reinforced plastics. However, the CNT yarn does not have remarkable mechanical properties such as the individual CNT. The most popular way for improving the mechanical properties of the CNT yarn is to make composites with polymer such as polyvinyl alcohol or polyimide. If some functional groups such as carboxyl groups are introduced on the surface of CNTs, interaction between the CNTs and the polymer is improved and high mechanical properties will be obtained. In this study, untwisted CNT yarns were prepared by drawing vertical aligned CNTs through a die and functionalized with mixed acid. Mixed acid introduced not only the functional groups but also defects on the surface of CNTs. For reducing the defects, the CNT yarn was graphitized at a temperature of 2800°C before the mixed acid treatment. By the graphitization treatment, crystallinity of the CNT yarn was improved and amorphous carbon was removed. As a result of XPS analysis, a graphitized CNT yarn treated with mixed acid did not contain the functional groups. On the other hand, a graphitized CNT yarn treated with hot mixed acid (90°C) contained the functional groups. Crystallinity of this yarn was 4.5 times higher than the as-received CNT yarn. In addition, as a result of single fiber tensile tests, tensile strength of this yarn was increased by 79 % and Young’s modulus was increased by 173 % compared to the as-received CNT yarn.

著者

新井 智貴 福島 槙一郎 世木 選 細井 厚志 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.84, no.863, pp.18-00039, 2018 (Released:2018-07-25)

参考文献数

14

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The effect of stress ratio on through thickness fatigue properties of thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers was evaluated. The unidirectional (UD) [088] and quasi-isotropic (QI) [45/0/-45/90]11S laminates were formed using prepregs (T800S/3900-2B) with toughened interlaminar layers. The spool shaped specimens were cut from the laminates. Static tensile and compressive tests were performed. As the results of the static tests on both laminates, the through thickness compressive strength was more than five times higher than tensile strength. The fracture morphology under compressive loading was difference between each laminate. Fatigue tests were performed under the stress ratio of R=0.1,-1,-3 and -6 on both laminates. As the results of the fatigue tests on both laminates, the fatigue life decreased as the stress ratio was lower. On the other hand, the remarkable difference of the fracture surface was not observed under each fatigue test condition by both macroscopic and microscopic observation in this study. The fatigue life of UD and QI specimens was able to be evaluated by the proposed model, the modified H-κ model based on strain energy approach. The predicted fatigue life was good agreement with the experimental results.

著者

細井 厚志 寺内 幹 角田 大 木村 達哉 古挽 彰 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.855, pp.17-00312-17-00312, 2017 (Released:2017-11-25)

参考文献数

25

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The effects of environment temperature on initiation and multiplication of transverse crack in cross-ply carbon fiber reinforced thermoplastic (CFRTP) laminates have been investigated. Static tensile tests for the cross-ply laminates and the 90° unidirectional laminates were carried out at room temperature, 93 °C and 130 °C, respectively. The transverse cracks were observed by soft X-ray photography. The tensile strength and the failure strain in the cross-ply laminates and the 90° unidirectional laminates at high temperature decreased compared to the values at room temperature. It was also found that the behavior of initiation and multiplication of the transverse cracks in the cross-ply laminates was changed due to the environment temperature. The experimental results under different temperature were analyzed by Weibull distribution on the basis of probabilistic model. Next, the energy release rate was calculated due to formation of a new micro crack based on the Weibull distribution. The predicted transverse crack density by Weibull distribution was compared with the experiment result and the reasonability of using Weibull distribution to CFRTP cross-ply laminates under high temperature was verified. It was found that the critical energy release rate of CFRTP laminates has decreased at high temperature and the experimental results showed that the matrix strength was decreased at high temperature. Also, the fiber-matrix interfacial fracture on the fracture surface of the 90° unidirectional laminates was observed in some areas at high temperature whereas the matrix fracture was observed at room temperature. Therefore, it was suggested that the interface strength between polymer and fiber was decreased at high temperature.

著者

世木 選 新井 智貴 福島 槙一郎 細井 厚志 藤田 雄三 武田 一朗 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.851, pp.16-00571-16-00571, 2017 (Released:2017-07-25)

参考文献数

15

被引用文献数

1

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Fatigue properties of the thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers in the out-of-plane direction (Z direction) and in the in-plane transverse direction (T direction) were evaluated experimentally. Spool specimens were machined from the thick mother plates which were laminated prepregs of T800S/3900-2B unidirectionally. The specimens were attached to metal tabs to apply loads in the thickness direction of the specimen. The tensile strengths in Z and T direction were measured by static tensile tests and S-N curves were obtained by fatigue tests at a stress ratio of R=0.1. As the results, the tensile strength in Z direction was 24% lower than that in T direction. Fatigue strength in Z direction at 106 cycles was also 25% lower than that in T direction. It was observed using a digital microscope that the fracture occurred in intralaminar layers in both static tensile tests and fatigue tests in Z direction. The thermal residual stress which was generated during the fabrication process and the stress distribution by mechanical loadings in spool specimens were calculated by finite element analysis. The calculated results showed that compressive residual stress applied in intralaminar layers in T direction by restraining the thermal deformation. It is found that the static tensile and fatigue properties in Z direction were almost the same as those in T direction by evaluating with the stresses applied in the nearest intralaminar layer to the minimum cross-section in the spool specimen.

著者

八田 博志 向後 保雄 棚次 亘弘 大鍋 寿一 水谷 智昭 川田 宏之 重村 卓

出版者

宇宙航空研究開発機構

雑誌

宇宙科学研究所報告 (ISSN:02852853)

巻号頁・発行日

vol.85, pp.1-26, 1996-03

被引用文献数

2

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ATREX用のタービンディスクには,航空機のものに較べてより高温とより高速回転が負荷される。本報告では,高温強度に優れ,軽量・低熱膨張係数を併せ持つ炭素繊維強化/炭素マトリックス(C/C)複合材料のATREX用のタービンディスク適用を検討した。 C/C複合材料を動的負荷がかかる一次構造物へ適用した例は殆ど報告されていない。そこで本論文の前半では,タービンディスクの開発を念頭に,関連すると推定されるC/C複合材料の基礎特性を示し,適用に際してのC/C複合材料の長所と短所を明らかにした。 C/C複合材料の利点は上記の他に,高面内靭性及び疲労負荷や集中応力に対する不敏感性が挙げられ,タービンディスクヘの適用に当たり問題になるのは,低層間強度・靭性及び耐環境性(耐酸化性を含む)であることを指摘した。前者に対する対策は三次元強化の採用が,後者に対してはSiCコーティング及び部分的な耐環境性セラミックスの適用が不可欠である。後半では,負荷荷重とC/C複合材料の特性の比較検討の結果たどり着いた二種類の候補構造,即ち一体構造と三分割構造を比較検討した。肉厚円盤から切削加工で製造される一体構造は成形上有利であるが,強化繊維の最適化が困難である。特に激しい捻れがあるファンブレード部の強化が最大の課題である。一方,ファンディスク,ファンブレード,及びタービンリングを接合する三分割構造は,強化繊維の最適化は比較的容易であるが,接合部強度と接合部の空隙や滑りなどから生じる不安定振動を如何に抑制するかが課題である。両モデルを比較すると現段階ではより高速回転が期待できる三分割構造が有望と言えよう。

著者

川田 宏之

出版者

産業開発機構

雑誌

映像情報industrial (ISSN:13461362)

巻号頁・発行日

vol.48, no.6, pp.69-72, 2016-06

著者

荒尾 与史彦 小柳 潤 武田 真一 宇都宮 真 川田 宏之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集A編 (ISSN:18848338)

巻号頁・発行日

vol.77, no.776, pp.619-628, 2011 (Released:2011-04-25)

参考文献数

17

被引用文献数

7 8

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Strict geometrical stability is required for the precise structures like telescopes. Unpredictable out-of-plane deformation is a serious problem when we use CFRP (Carbon Fiber Reinforced Plastic) laminate to the precise structure. This out-of plane deformation of symmetrical CFRP laminate mainly arise from combination effects of ply angle misalignment and temperature change. We discussed here is effective stacking sequence of CFRP laminate that mitigate the deformation caused by the ply angle misalignment. The analysis based on laminate theory was performed to calculate the thermal deformation. In this analysis, the random numbers were added to each layers as ply angle misalignments. The analytical results were obtained statistically by Monte Carlo method. Mohr's curvature circle was also incorporated to evaluate the deformation as P-V (peak to Valley) values. We performed the analysis with various stacking sequence. It was calculated that the symmetric cross-ply laminates deformed 10 times larger than the other quasi-symmetric laminates. In the case of the total ply number is less than 12, the stacking sequence in the laminate has a significant effects on the thermal deformation. However, if the total number ply number is more than 24, effect of stacking sequence on the thermal deformation becomes negligible. We also discussed the geometrical stability of CFRP mirror by considering unavoidable ply angle misalignment. It was presumed that the CFRP mirror can be used for wide range of wave length when the back structure was attached to CFRP laminates.