研究者データベース
大島 草太OSHIMA Sotaオオシマ ソウタ
| ■所属部署名 | 工学研究院 機械システム工学部門 | |||
| ■職名 | 准教授 | |||
Last Updated :2026/07/29
業績情報
氏名・連絡先
氏名
オオシマ ソウタ, 大島 草太, OSHIMA Sota
主たる所属・職名
工学研究院 機械システム工学部門, 准教授
学位
科学研究費助成事業
- 若手研究
微視的損傷進展に伴う非線形挙動を考慮したCFRPの亀裂進展挙動評価とメカニズム解明
自 2024年, 至 2026年 - 基盤研究（B）
CFRPのガスバリア機能発現メカニズムの解明と物理モデルの構築
自 2025年, 至 2025年 - 基盤研究（A）
複合材料の資源循環設計を実現するデジタルモデリング基盤の創出
自 2025年, 至 2025年
論文
- Mesoscale mechanism of damage in fracture process zone of CFRP laminates simulated with triaxial stress state-dependent constitutive equation of matrix resin
Oshima, Sota; Seryo, Yuji; Kimura, Masao; Hojo, Masaki
COMPOSITES SCIENCE AND TECHNOLOGY
ELSEVIER SCI LTD
The three-dimensional failure process experimentally observed by synchrotron radiation X-ray computed tomography (SR X-CT) regarding the influence of the interfiber distance is discussed on the basis of the results of numerical experiments. Triaxial stress states in the fracture process zone of carbon fiber reinforced polymers were analyzed on the mesoscale under mode I and mixed-mode (mode I + II) loading. Yield and damage models depending on stress triaxiality were used to accurately simulate three-dimensional stress states in the damage zone around the crack tip. Owing to the heterogeneity of composites, deviatoric stress is prominent in the thin resin region where the interfiber distance is small under mode I loading. On the other hand, matrix resin is triaxially stressed in the middle point between carbon fibers in the thick resin region where the interfiber distance is large. Under mode II loading, the shapes of fiber/matrix debonding depended on the interfiber distance. Areas with stress concentration were found owing to a large debonding area in the thick resin region resulting in a matrix cracking-prone stress state. These findings explain the damage and failure processes well observed by SR X-CT and provide a fundamental understanding of the damage mechanism at a mesoscale.
2024年10月20日, 研究論文（学術雑誌）, 共同, 257, 0266-3538, DOI(公開)(r-map) - Application of the size effect law to the determination of R-curves for transverse cracking in polymer matrix composite laminates using single edge notched bend specimens
Kusaka, Takayuki; Oshima, Sota; Gao, Chong
ENGINEERING FRACTURE MECHANICS
PERGAMON-ELSEVIER SCIENCE LTD
The R-curves for transverse cracking could be determined based on the size effect law using SENB specimens, where the R-curves determined by the size effect law were consistent with those determined by the compliance method. The crack growth resistance in the steady-state and the crack extension at the onset of the steady-state of carbon-fiber/epoxy laminates, T800S/2592, were determined to be 0.22 N/mm and 0.36 mm, respectively. The crack growth stability in SENB specimens depended not only on the load control method but also on the specimen geometry, whereas a unique R-curve could be obtained regardless of the crack growth stability.
2024年10月01日, 研究論文（学術雑誌）, 共同, 309, 0013-7944, DOI(公開)(r-map) - Experimental and numerical investigation of mesoscopic damage accumulation in adhesively bonded composite scarf joints
Oshima, Sota; Satoshi, Kobayashi
COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING
ELSEVIER SCI LTD
Mesoscopic damage accumulation in adhesively bonded composite scarf joints until final failure was investigated for a comprehensive understanding of the damage and failure processes. The damage accumulation in scarf joints with different scarf angles and stacking sequences was characterized by several in situ techniques, such as optical microscopy, high-speed photography, and acoustic emission testing. In addition, progressive damage analysis was carried out to understand the stress state depending on damage using the finite element method with stress triaxiality-dependent yield and damage models. Transverse cracks appeared in composite adherends because of local stress concentration near the end of the 0 layers. The final failure was triggered by the interfacial crack growth between the 0 and 90 layers initiated from the transverse cracks. Numerical simulation results showed that the presence of transverse cracks largely affects the stress distribution in the adhesive layer.
2024年04月, 研究論文（学術雑誌）, 共同, 179, 1359-835X, DOI(公開)(r-map) - Large-displacement post-buckling response and cyclic reliability of Cu-Al-Mn shape memory alloy actuators for spacecraft deployable thermal radiators
Matsueda, Rina; Ong, Fei Shen; Oshima, Sota; Tobe, Hirobumi; Sato, Eiichi; Kitazono, Koichi
ACTA ASTRONAUTICA
PERGAMON-ELSEVIER SCIENCE LTD
This study demonstrates the potential of single-crystalline Cu-Al-Mn shape memory alloys (SMAs) for use as smart actuators in deployable thermal radiators, aiming to reduce spacecraft costs and weight. The SMA actuators are designed to axially displace via buckling to half of their initial length, minimizing storage space and maximizing deployment stroke. Slender polycrystalline, near-oligocrystalline, and single-crystalline Cu-Al-Mn SMA samples were fabricated using a cost-effective cyclic heat-treatment process and subjected to 100 cycles of large-displacement axial compression testing in superelastic mode. The performance was evaluated based on deformation uniformity, length recoverability, and end-load stability. Single-crystalline samples, with a tensile transformation strain of approximately 6.0%, exhibited symmetrical post-buckling deformation, over 90% length recoverability, and stable end-load behavior. In contrast, near-oligocrystalline samples, with grain sizes comparable to or larger than their width and thickness, demonstrated the largest tensile transformation strain ( 8.0%) but exhibited asymmetrical deformation and highly inconsistent performance. Finite element analysis indicated that this behavior resulted from nonhomogeneous martensitic transformation and asymmetrical stiffness due to weakly constrained grains with varying transformation stresses. Polycrystalline samples, with smaller grain sizes relative to their width and thickness, exhibited symmetrical deformation but showed the smallest tensile transformation strain ( 2.0%), leading to the lowest length recoverability. These findings underscore the importance of considering both transformation behaviors and the grain-size-to-sample-dimension ratios when optimizing the performance of slender SMA structures operating in post-buckling modes.
2025年03月, 研究論文（学術雑誌）, 共同, 228, 0094-5765, DOI(公開)(r-map), 607 - Effect of matrix resin types on R-curves and microscopic failure processes during transverse cracking in CFRP laminates
Oshima, Sota; Salviato, Marco; Ushijima, Keita; Sugiura, Naoki
COMPOSITE STRUCTURES
ELSEVIER SCI LTD
R-curves of carbon fiber reinforced polymer (CFRP) laminates were obtained during transverse cracking using the size effect law of the fracture toughness specimens. The CFRP laminates were composed of high-modulus polyacrylonitrile (PAN)-based carbon fibers and three different matrix resins. Since debonding between high-modulus PAN-based carbon fibers and matrix resin occurs at a lower applied stress, two modified resins were prepared to enhance their performance. Failure processes were observed in situ using a high-magnification optical microscopy system. This allowed for a correlation between the microscopic failure processes and the R-curves, providing insight into the underlying mechanisms of transverse cracking. Both the R-curves and microscopic failure processes were significantly influenced by the matrix resins. With the unmodified matrix resin, debonding between the carbon fibers and the matrix, as well as large deformation of the matrix resin in the debonded regions, was observed. In contrast, debonding was less pronounced with the modified matrix resins. A modified, flexible matrix resin exhibited ductile and cohesive failure, whereas a modified yet stiffer matrix resin resulted in brittle failure. These findings suggest that interfacial and resin properties, along with changes in stress states, contribute to the microscopic failure processes. This study provides a fundamental understanding of transverse cracking mechanisms at the microscale.
2025年11月15日, 研究論文（学術雑誌）, 共同, 372, 0263-8223, DOI(公開)(r-map) - Quantitative assessment of signal quality and usability of EEG and EMG recordings with PEDOT:PSS-coated microneedle electrodes
Yamaguchi, Tomoya; Kurashina, Yuta; Nagahara, Eiji; Oshima, Sota; Kaneko, Naotsugu; Nakazawa, Kimitaka; Tanaka, Hideyuki; Yokoyama, Hikaru
FRONTIERS IN NEUROSCIENCE
FRONTIERS MEDIA SA
Introduction Bioelectrical signals are vital indicators of physiological function, psychological status, and clinical conditions. However, traditional wet electrodes using conductive gel are time-consuming, labor-intensive, and degrade over time due to gel drying. Recently, microneedle (MN) electrodes coated with poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have been developed for high-quality signal acquisition. Although low electrode-skin impedance has been demonstrated on hairless regions, their use in electroencephalography (EEG) recordings on hairy scalp areas and quantitative comparisons with conventional electrodes in both EEG and electromyography (EMG) remain limited.Methods We fabricated two MN electrode types of different lengths-one for EMG on hairless skin and one for EEG on the hairy scalp-and compared them with conventional wet and dry electrodes. EMG was recorded during a force-matching task; EEG was assessed via somatosensory evoked potentials. We also evaluated setup/cleanup time, comfort, and pain during EEG measurement.Results For EMG, MN electrodes achieved significantly higher signal-to-noise ratios than conventional electrodes. For EEG, they outperformed dry electrodes and matched wet electrodes in signal quality-without using conductive gel. Although additional time was required to part hair, cleanup was faster due to the absence of gel. Pain was comparable to dry electrodes.Discussion PEDOT:PSS-coated MN electrodes provided superior EMG signal quality and high-quality EEG signals comparable to wet electrodes even without gel. These findings suggest that PEDOT:PSS-coated MN electrodes offer a compelling balance of signal quality and user convenience, making them especially advantageous for real-world and clinical applications where time efficiency, minimal discomfort, and gel-free operation are critical.
2025年12月03日, 研究論文（学術雑誌）, 共同, 19, DOI(公開)(r-map) - Review on Damage and Failure in Adhesively Bonded Composite Joints: A Microscopic Aspect
Oshima, Sota; Koyanagi, Jun
POLYMERS
MDPI
Adhesively bonded joints offer numerous advantages for industrial applications. However, because damage and failure in adhesively bonded joints occur within thin adhesive layers between stiff adherends, experimental characterization and numerical simulation that account for microscopic phenomena are particularly challenging. For adhesively bonded composite joints, in particular, the interaction between adhesive and adherend damage must also be carefully considered. This review article mainly discusses and reviews the microscopic aspects of damage and failure in adhesively bonded composite joints for aerospace applications. Three main topics are addressed in this article. First, the peculiar deformation and damage behaviors of polymeric materials, including their dependence on stress triaxiality, are discussed. Second, the experimental characterization of deformation and damage in adhesive layers using advanced microscale inspection techniques is reviewed. Lastly, the modeling and numerical simulation of damage and failure processes, incorporating microscopic phenomena, are explored. The article concludes with a discussion of future perspectives.
2025年02月, 研究論文（学術雑誌）, 共同, 17, 3, DOI(公開)(r-map)