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Search Results: 1 - 10 of 2549 matches for " Akira Todoroki "
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Effect of Degree of Cure on Sandwich Structural Capacitor Using Ion-Conductive Polymer with Carbon Fabric Skins  [PDF]
Akira Todoroki
Open Journal of Composite Materials (OJCM) , 2016, DOI: 10.4236/ojcm.2016.64011
Abstract: Structural capacitors are composite structures that function as energy storage capacitors. An electric double-layer capacitor with a composite structure using a solid polymer electrolyte matrix with a glass fiber fabric separator has recently been developed. In the present study, new foam core sandwich structure is adopted and the effect of the degree of cure is experimentally investigated. Carbon fiber fabric cloth is used as electrodes, and the polystyrene foam core is used as separator. Material system of Poly Ethylene Glycol DiGlycidyl Ether (PEGDGE) with Lithium bisTriFluoromethane Sulfonyl Imide (LiTFSI) and hardener of TriEthylene TetrAmine (TETA) is adopted as ion-conductive polymer matrix. The effect of the cure degree is experimentally investigated by using 100% cure degree, 70% cure degree and 0% cure degree specimens. As a result, the polystyrene foam-core sandwich system is proved to be effective, but the capacitance is not enough because of the lack of surface area of the carbon fiber electrodes. As the remained TETA impedes the movement of Li+ cation in the solid polymer by means of the segment-motion-assisted diffusion process, the low degree of cure causes small capacitance with this material system.
Wireless Monitoring of Automobile Tires for Intelligent Tires
Ryosuke Matsuzaki,Akira Todoroki
Sensors , 2008, DOI: 10.3390/s8128123
Abstract: This review discusses key technologies of intelligent tires focusing on sensors and wireless data transmission. Intelligent automobile tires, which monitor their pressure, deformation, wheel loading, friction, or tread wear, are expected to improve the reliability of tires and tire control systems. However, in installing sensors in a tire, many problems have to be considered, such as compatibility of the sensors with tire rubber, wireless transmission, and battery installments. As regards sensing, this review discusses indirect methods using existing sensors, such as that for wheel speed, and direct methods, such as surface acoustic wave sensors and piezoelectric sensors. For wireless transmission, passive wireless methods and energy harvesting are also discussed.
Electrical Shorting between the Carbon-Fiber Cloth Electrodes of Structural Capacitors with a Glass-Fiber Cloth Separator  [PDF]
Akira Todoroki, Hiroko Shiomi, Yoshihiro Mizutani, Yoshiro Suzuki
Open Journal of Composite Materials (OJCM) , 2014, DOI: 10.4236/ojcm.2014.43016

Multifunctional composites that have the ability to store or generate energy have attracted huge attention recently. One type of multifunctional composite is a structural capacitor that uses carbon fiber cloth as electrodes separated by glass-fiber cloth. However, such structural capacitors are difficult to fabricate reliably because electrical shorts sometimes form between the electrodes. In the present study, we investigate the mechanism of electrical shorting in such capacitors, which allows us to propose an improved fabrication process to prevent electrical shorting between the carbon-cloth electrodes. Infrared thermography reveals that electrical shorting between the electrodes is caused by contact between the carbon-fiber electrodes. Such contacts are formed by movement of the glass fibers of the separator during curing, which is induced by epoxy resin flow. Pre-curing of the glass-fiber cloth separator to a suitable degree ensures that the electrical insulation between carbon-fiber electrodes is reliable.

Electrical Resistance Change of Carbon/Epoxy Composite Laminates under Cyclic Loading under Damage Initiation Limit  [PDF]
Akira Todoroki, Daichi Haruyama, Yoshihiro Mizutani, Yoshiro Suzuki, Tesuo Yasuoka
Open Journal of Composite Materials (OJCM) , 2014, DOI: 10.4236/ojcm.2014.41003

Self-sensing multifunctional composite has sensing function using electrical resistance changes. Carbon Fiber Reinforced Polymer (CFRP) composite is one of the self-sensing multifunctional composites. For the reliability of the self-sensing, electrical contact between the lead wire and the carbon fibers is the most important issue. The present study focuses on the effect of the cyclic loading of lower applied strain range than the fatigue damage level. As a result, the electrical contact resistance at the copper electrode increased with the increase of cycles. That means that the electrical change at the electrodes must be considered for the long-term self-sensing monitoring system. When a four-probe method is used to measure the electrical resistance, the contact resistance effect is minimized. Moreover, angle-ply laminates have plastic deformation caused by shear loading, and that causes electrical resistance decrease during the cyclic loading. Cross-ply laminates of CFRP composites have no electrical resistance increase without damage. Quasi-isotropic laminates of CFRP composites, however, have electrical resistance decrease with the increase of the number of cycles because of the plastic deformation of the angle-ply laminates.

Self-Sensing TDR for Bearing Failure Detection of CFRP Laminate Fastener Hole with Particular Reference to the Effect of Fasteners  [PDF]
Akira Todoroki, Keisuke Ohara, Yoshihiro Mizutani, Yoshiro Suzuki, Ryosuke Matsuzaki
Open Journal of Composite Materials (OJCM) , 2015, DOI: 10.4236/ojcm.2015.53009
Abstract: Carbon fiber reinforced polymer composites (CFRP) have been applied to aerospace and automobile structures. For many CFRP structures, mechanical metallic fasteners are usually adopted. For the fasteners used in internal structures such as a wing box, the damage to the CFRP structures around fastener holes is visually quite difficult to find. A simple method to find the damage around fastener holes is required. In this study a self-sensing time domain reflectometry (TDR) method is newly applied to detect bearing failure around the fastener holes of CFRP structures. A microstrip-line method is generally used to create a transmission line. When the transmission line is mounted near the metallic fasteners, they may affect the impedance of the transmission line. In this study, the effect of distance between the fasteners and the transmission line was numerically investigated using a finite difference time domain analysis method. After finding the appropriate distance, experiments were performed to detect the bearing failure around a fastener hole. The experiments showed the performance of the self-sensing TDR for detecting bearing failure.
Supercapacitor Consisting of a Form Core Sandwich with Woven Carbon Fiber Skin  [PDF]
Akira Todoroki, Tomohiro Sawada, Yoshihiro Mizutani, Yoshiro Suzuki
Open Journal of Composite Materials (OJCM) , 2015, DOI: 10.4236/ojcm.2015.54013
Abstract: Structural capacitors are composite structures that function as energy storage capacitors. Parallel plate-type capacitors have the advantage of high voltage resistance, but are limited by low capacitance. An electric double-layer capacitor with a composite structure using a solid polymer electrolyte matrix with a glass fiber fabric separator has recently been developed. However, the solid polymer electrolyte caused the capacitor to possess high internal resistance. In the present study, a new design of supercapacitor using a form core sandwich with high water retention is proposed and experimentally investigated. Activated carbon sheets are used as electrodes on the form core sandwich to make a supercapacitor. Woven carbon fabric is used as lead wires of the supercapacitor. The resulting supercapacitor displays a low surface resistance of 810 Ωcm2 and high areal capacitance of 520 mF/cm2.
Self-Sensing Curved Micro-Strip Line Method for Damage Detection of CFRP Composites  [PDF]
Akira Todoroki, Kazuhiro Yamada, Yoshihiro Mizutani, Yoshiro Suzuki, Ryosuke Matsuzaki, Hiroyasu Fujita
Open Journal of Composite Materials (OJCM) , 2014, DOI: 10.4236/ojcm.2014.43015

A self-sensing Time Domain Reflectometry (TDR) method for Carbon Fibre Reinforced Polymer (CFRP) laminates has been propped in the present study: carbon fibres are used as sensors using a transmission line. Authors have published research articles of the self-sensing TDR method. The self-sensing TDR method reduces number of required electrodes for damage detections although the sensitivity of detection is sacrificed. A micro-strip line (MSL) method is adopted to obtain impedance matching with a coaxial cable and successfully detected damage in a CFRP laminate in the previous study. In the present study, a long curved MSL is experimentally investigated as an impedance-matched transmission line for detection of damage of a CFRP laminate in wider area. Fibre breakage is simulated as a hole made by drilling. As a CFRP laminate has strongly orthotropic electric conductance and the electric properties of a CFRP laminate at the high frequency are not clarified, the effect of the orthotropic conductance at the curved transmission line is experimentally investigated. As a result, the effect of orthotropic conductance at the curved strip line is shown to be negligible, and fiber breakage that locates closed to the copper strip line can be detected by the self-sensing curved MSL method. It is, however, difficult to detect damage far from the copper strip line.

3D Printing of Continuous Carbon Fibre Reinforced Thermo-Plastic (CFRTP) Tensile Test Specimens  [PDF]
Frank Van Der Klift, Yoichiro Koga, Akira Todoroki, Masahito Ueda, Yoshiyasu Hirano, Ryosuke Matsuzaki
Open Journal of Composite Materials (OJCM) , 2016, DOI: 10.4236/ojcm.2016.61003
Abstract: A study was conducted to evaluate the current production capabilities of the Mark One? 3D printer in printing carbon fibre reinforced thermoplastic (CFRTP) tensile test specimens according to the JIS K 7073 by making use of fused deposition modelling. Several different types of CFRTP tensile test specimens are printed and are tensile tested in the longitudinal direction to obtain an overview of the mechanical properties of 3D printed CFRTP material. These properties are compared with the literature values known for composite materials to see if these agree. The main goal of this research is to increase the knowledge of the 3D printing process of CFRTP and to later use this knowledge to further improve the 3D printing process to obtain stronger 3D printed CFRTP materials.
Fiber Line Optimization in Single Ply for 3D Printed Composites  [PDF]
Yusuke Yamanaka, Akira Todoroki, Masahito Ueda, Yoshiyasu Hirano, Ryosuke Matsuzaki
Open Journal of Composite Materials (OJCM) , 2016, DOI: 10.4236/ojcm.2016.64012
Abstract: In conventional manufacturing processes of composites, Carbon Fibre Reinforced Plastic (CFRP) laminates have been made by stacking unidirectional or woven prepreg sheets. Recently, as a manufacturing process of CFRP, 3D printing of CFRP composites has been developed. The 3D printing process of CFRP composites enables us to fabricate CFRP laminates with arbitrary curvilinear fibre plies. This indicates that the optimization of the in-plane curved carbon fibre placement in a planar ply is strongly required to realize superior 3D printed composites. In the present paper, in-plane curved carbon fibre alignment of a ply with an open hole is optimized in terms of maximization of the fracture strength. For the optimization process, a genetic algorithm is adopted. To describe curved carbon fibre alignments in a planar ply, stream lines of perfect flow is employed. By using the stream lines of the perfect flow, number of optimization parameters is significantly reduced. After the optimization, the fracture strength of CFRP laminate is compared with the results of unidirectional CFRP ply. The curved fibre placement in a planar ply shows superior fracture improvement.
Frequency Dependence of the b-Value Used for Acoustic Emission Analysis of Glass Fiber Reinforced Plastics  [PDF]
Do Yun Jung, Yoshihiro Mizutani, Akira Todoroki, Yoshiro Suzuki
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.73007
Abstract: Acoustic Emission Testing (AT) is one of the major non-destructive testing methods used for severity evaluation of structures. Amplitude distributions of AE signals are characterized by b-value and the value is mainly used for the severity evaluation of concrete structures until now. The value is assumed to be independent with propagation distance between acoustic emission sources to AE sensors. We evaluate the influence of the wide frequency band encountered in the fracture behavior of glass fiber reinforced plastic (GFRP) on the b-value analysis. In tensile tests, the b-value was determined from an acoustic emission (AE) source generated near a centered hole in a specimen of GFRP. At 15 mm from the hole, the b-value analysis indicated a decreasing trend with increasing tensile stress. At a propagation length of 45 mm, farthest from the hole, a?small number of AE signals were received. The attenuation is more rapid for high-frequency AE signals. Thus, the amplitude distribution bandwidth is wide and the b-value changes. This change in b-value for GFRPs is investigated by analyzing the spectral components of the AE signals. For a single-frequency AE source, the b-value is unchanged with propagation length. In contrast, multiple-frequency AE sources produce changes in b-value proportional to the fraction of each spectral component in the received signal. This is due to the frequency dependence of the attenuation with propagation length.?From these results, the b-value analysis cannot be applied to considering frequency dependence of AE attenuation.
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