炭素繊維強化プラスチック(CFRP)積層板は,高強度・高剛性など優れた機械的特性を有し,かつ軽量であるため,航空機の1次構造材料に適用されるなど,今後は自動車や高速鉄道車両など,金属に替わる構造材料としての適用が期待されている.CFRP積層板は一般に疲労に強い材料として知られているが,10^7サイクルを超える超長寿命域における損傷成長挙動について十分な評価は未だなされておらず,構造材料としての長期信頼性が確立されていない現状にある.これまでの研究で,高サイクル疲労領域におけるCFRP積層板の損傷進展挙動は,従来と異なる破壊形態を示すことを明らかとした.しかし,従来と異なる損傷の進展挙動については,未だ定量的評価はなされていなかった,そこで,本研究では,高サイクル疲労領域における実験データを蓄積するとともに,高サイクル疲労領域におけるCFRP積層板の損傷をモデル化し,その進展挙動について定量的に評価を行うことを目的とした.まず,負荷応力レベルに依存したCFRP積層板の損傷形態の違いについて定量的に評価を行った.層内樹脂割れ(トランスバースクラック)を考慮した層間剥離進展について,単位長さ当たりの損傷進展に伴い解放されるエネルギを導出した.さらに,Paris則を応用して損傷進展速度と損傷進展に伴い解放されるエネルギの関係について,トランスバースクラック進展及び層間剥離進展のそれぞれを定量的に評価した.その結果,低エネルギレベル(低応力レベル)域では層間剥離が進展しやすく,高エネルギレベル(高応力レベル)域ではトランスバースクラックが進展しやすい結果を得た.この結果は,実験結果とよい一致を示した.また,破断応力の20%を最大応力に設定した疲労試験では,繰返し数3×10^8サイクルまで,損傷は観察されなかった.
1 0 0 0 OA 海水浸漬における平織CFRP積層板の静的引張強度及び疲労強度劣化特性の評価
- 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
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.
1 0 0 0 OA 熱混酸処理を用いた黒鉛化無撚カーボンナノチューブ糸の官能基化および高強度化
- 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
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
- 謝 毅源 細井 厚志 巨 陽
- 出版者
- 一般社団法人 日本機械学会
- 雑誌
- 東海支部総会講演会講演論文集
- 巻号頁・発行日
- vol.2014, pp._109-1_-_109-2_, 2014
1 0 0 0 OA 一方向および擬似等方層間高靭性化厚肉CFRP積層板の面外方向疲労特性に及ぼす応力比の影響
- 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
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
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
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.