Hokkaido University · Engineering
Professor Kosuke Takahashi's research lab specializes in advanced functional materials and structural health monitoring, with a focus on graphite/polymer composites, radical chemistry for borane-based synthesis, and the development of smart materials for renewable energy systems. The lab investigates the electrical and mechanical behavior of composite materials under thermal and mechanical stress, while pioneering innovative non-destructive evaluation techniques such as the addressable conducting network for real-time damage detection. Additionally, the group develops novel synthetic methodologies using N-heterocyclic carbene boranes for creating thermally stable, functional materials, including liquid crystals and high-performance polymers. Their work bridges materials chemistry, mechanical engineering, and structural integrity assessment, particularly in wind energy applications and carbon fiber composites.
Figures are computed from collected data and may differ slightly.
This article investigates the dependency of electrical resistance on temperature for graphite/polymer composites. The electrical resistance change of a unidirectional laminate is measured with elevated temperature in the fiber, transverse and through-thickness directions. Because of the properties of graphite fibers, the electrical resistance decreases as temperature increases in any direction. The activation energy is calculated from an Arrhenius plot to evaluate the difference among the differ
Monohydroboration of substituted 1,3-diynes with an <i>N</i>-heterocyclic carbene borane (NHC-borane) occurs under radical conditions using an azo initiator, such as ACCN and AIBN, and a thiol as a polarity-reversal catalyst. The reaction is highly regio- and stereoselective and provides stable NHC-(<i>E</i>)-alkynylalkenylboranes.
Polyfluoroarenes work as good radical acceptors in the thermal radical reaction with N-heterocyclic carbene boranes (NHC-boranes) in the presence of di-<i>tert</i>-butyl peroxide. In this reaction, a C-F bond of polyfluoroarenes is substituted with an NHC-boryl group to provide <i>B</i>-aryl NHC-borane derivatives. The developed synthetic method was applied to the synthesis of novel borane-containing liquid crystalline molecules having highly thermal stability.
Due to changes in wind, the torque obtained from the wind turbine always fluctuates. Here, the wind turbine and the rotor of the generator are connected by a shaft that is one elastic body, and each rotating body has different inertia. The difference in inertia between the wind turbine and the generator causes a torsion between the wind generator and the generator; metal fatigue and torsion can damage the shaft. Therefore, it is necessary to consider the axial torsional vibration suppression of
The initial stage of fatigue failure has not been thoroughly clarified for carbon fiber reinforced plastics (CFRPs). Although the initiation of fatigue cracks has been regarded to be interfacial debonding between the carbon fiber and polymer matrix, their detection among numerous carbon fibers, whose diameter is only 7 µm, is extremely difficult. In this study, a single carbon fiber was transversely embedded in a dumbbell-shaped epoxy sample to focus on the interfacial debonding and was observed
The electrical resistance change method (ERCM) has long been an area of interest as an in-service health monitoring system. To apply the ERCM to existing structures, a new concept, the addressable conducting network (ACN), is proposed for autonomic structural health management of graphite/polymer composites. The ACN consists of two sets of conducting lines normal to each other, where one set resides on the top surface of the laminate and the other on the bottom surface. Damage can be detected by
This study extensively investigates the fibrillation process of a pressure-sensitive adhesive (PSA) using a probe-tack test. It was conducted using a glass sphere at the millimeter scale for various thicknesses of PSA layers laminated on a glass substrate, on various contact areas. A sharp decrease in the adhesion force caused by cavity growth was confirmed in the case of large contact areas, whereas cavities were not generated in the case of small contact areas on the thick PSA layer. Furthermo
The adhesive force generated by a small short-term pressure, called tack, is measured by a probe tack test on pressure-sensitive adhesives (PSAs); the maximum force is evaluated by cavity growth at the interface between the PSA layer and the probe surface. As the PSA layer becomes thinner, it is more difficult to measure the tack with a cylindrical probe because of the uneven contact resulting from misalignment. A spherical probe is preferable to obtain reproducible contact on the PSA layer, but
This article considers the practical use of electrical resistance change method (ERCM) for damage detection in graphite/polymer composites. ERCM utilizes the high electrical conductivity of graphite fibers in the composites and can detect damage by change in electrical resistance. Since the effectiveness of ERCM has been shown extensively in the literature, it is now necessary to consider how to apply ERCM into existing structures. For practical use of ERCM, a new concept of an addressable condu
In this study, the effect of a tackifier on the viscoelastic and adhesion properties of acrylic pressure-sensitive adhesives (PSAs) was investigated. The intermediate products in the process of PSA synthesis, including an acrylate-based copolymer solution, a cross-linked copolymer, and the final product with a tackifier, were prepared and characterized using dynamic mechanical analysis (DMA). A significant increase in storage and loss moduli at high angular velocities was observed for the final
Statistical diagnosis using electrical resistance changes is performed to detect a delamination crack in a CFRP beam. This method enables to reduce data required for damage identification. First, a new measuring method of multiple electrical resistance changes is proposed to perform statistical diagnosis. The proposed method measures electrical resistance changes of multiple segments in a CFRP beam although electrical interference must be considered when multiple voltages are charged at once. Ne
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