Tomohiro Yokozeki

The University of Tokyo

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Takahira Aoki

The University of Tokyo

Ryo Higuchi

The University of Tokyo

Toshio Ogasawara

Tokyo University of Agriculture and Technology

Takashi Ishikawa

Paul Scherrer Institute

Vipin Kumar

Oak Ridge National Laboratory

Tatsuhiro Takahashi

Yamagata University

Masahito Ueda

Nihon University

Natsuki Tsushima

Japan Aerospace Exploration Agency

Yutaka Iwahori

Meiji University

Teruya Goto

Yamagata University

Cooperative Institutions

The University of Tokyo

101

Japan Aerospace Exploration Agency

Tokyo University of Science

Tohoku University

Nagoya University

Tokyo Institute of Technology

Kyoto University

Institute of Space and Astronautical Science

University of Tsukuba

Academy of Scientific and Innovative Research

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3D PRINTED LAYER OF POLYANILINE-BASED CONDUCTIVE POLYMER FOR LIGHTNING STRIKE PROTECTION OF CFRPS

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (2019)

Vipin Kumar Ryan Spencer Justin Condon Tyler C. Smith Tomohiro Yokozeki

Lightning

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Citations (1)

Development of Variable Camber Morphing Airfoil Using Corrugated Structure

Journal of Aircraft (2014)

Tomohiro Yokozeki Aya Sugiura Yoshiyasu Hirano

This paper describes the development and the wind tunnel test of a variable geometry morphing airfoil using corrugated structures. Proof-of-concept study of a morphing wing with corrugated flexible seamless flap-like structure is verified by finite element analysis, and a prototype is manufactured using carbon fiber reinforced plastics. For the actuation system, two servomotors are installed inside the prototype wing to control the airfoil shape by the chordwise tension of the connected wires. Successful actuation of the prototype wing is demonstrated under the air speed up to in the wind tunnel test. Basic aerodynamic properties are also evaluated in comparison to traditional airfoil with a hinged control surface. Lift increase of variable corrugated wing is recognized compared to the traditional wing when the aileron angle increases.

Aileron

Camber (aerodynamics)

Morphing

10.2514/1.c032573

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Citations (106)

Permeation-after-impact Properties of CFRP Laminates for Use on Propellant Tank

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES SPACE TECHNOLOGY JAPAN (2009)

Tomohiro Yokozeki Akiko Kuroda Akinori Yoshimura Toshio Ogasawara Takahira Aoki

This paper describes the experimental study of impact testing and permeability testing of CFRP laminates for application of propellant tanks considering the reliability of the tank structures associated with foreign object impact damage. Three types of quasi-isotropic laminates with different laminate thickness were prepared and subjected to transverse impact tests, nondestructive inspections, and helium gas permeation tests in series. Transverse impacts induced delaminations, matrix cracking, and fiber breakage, which caused severe through-thickness gas leakage. Effects of impact energy and laminate thickness on the permeation-after-impact properties are discussed, and the critical damage mode controlling the severe gas leakage is identified.

Impact energy

Breakage

Leakage (economics)

Penetration (warfare)

10.2322/tstj.7.pc_19

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Aeroelastic Simulation and Experimental Validation of a 3D-Printed Passive Morphing Airfoil

AIAA Journal (2024)

Shuji Ochi Shoko Kai Kohei Takase Kensuke Soneda Taro Imamura

To predict the deformation and aerodynamic performance of a passive morphing airfoil with a novel compliant structure, aeroelastic simulation methods were developed. The static aeroelastic problem was solved by loosely coupling a finite-element-method solver and a hierarchical Cartesian grid-based flow solver. The viscous effect was investigated by comparing the results of using the Euler and Reynolds-averaged Navier–Stokes (RANS) equations in the aerodynamic simulations. The accuracies of the structural and aerodynamic solvers were validated through structural and wind-tunnel experiments, respectively. The deformation predicted by the RANS-based aeroelastic simulation was in accordance with the experimental results, while the Euler-based aeroelastic simulation predicted a larger deformation. The lift slope of the morphing airfoil improved more than that of the rigid airfoil, showing consistency with the experimental results. The comparative study showed that the viscous flow condition leads to a smaller aerodynamic load and deformation of the morphing airfoil.

Aeroelasticity

Morphing

NACA airfoil

10.2514/1.j063000

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Citations (3)

On the specimen for interfacial fracture toughness evaluation of foam-core sandwich structures

Advanced Composite Materials (2012)

Tomohiro Yokozeki

Abstract Foam-core sandwich specimens for interfacial fracture toughness measurement are designed based on the prediction method of steady-state crack location in foam-core sandwich beams using the crack deflection model developed previously. This paper derives the necessary condition that the face sheet debonding grows along the interface between the face sheet and the core during the fracture toughness tests. The recommended specimen thickness ratios for several testing methods are presented. Finally, the physical meaning of the derived condition is explained, and the effect of residual thermal stresses on the condition is discussed. Keywords: foam-core sandwichfracture toughness testdebondingspecimen designcrack kinking Acknowledgment The author gratefully acknowledges the support of Mizuho Foundation for the Promotion of Sciences.

Aluminium foam sandwich

10.1080/09243046.2012.743717

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Citations (3)

Effects of Process-Induced Fiber Bundle Waviness on the Flexural Strength of Carbon Fiber Reinforced Thermoplastic Composites

Tomohiro Yokozeki Takahira Aoki Kotaro Akakabe Akira KOBIKI

This study focuses on the process-induced fiber bundle waviness in carbon fiber reinforced thermoplastic composites (CFRTP). Fiber bundle waviness is often observed in manufactured CFRTPs, which deteriorates the mechanical properties. This study experimentally investigates the quantitative measurement of fiber bundle waviness in unidirectional CFRTP using the optical microscope and the X-ray CT scanning. Flexural mechanical properties are measured in relation to the magnitude of the included fiber waviness. Strength deterioration is experimentally evaluated as a function of the fiber waviness parameter.

Waviness

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The effect of matrix cracks on gas permeability through CFRP laminates

Advanced Composite Materials (2004)

Tomohiro Yokozeki Takahira Aoki Takashi Ishikawa

Abstract Diffusion-controlled gas permeability through CFRP laminates was experimentally investigated as fundamental research on the feasibility of composite propellant tanks. Using helium gas and a helium leak detector, through-the-thickness gas permeability in CFRP laminated tubes with or without matrix cracks was measured at room temperature. The effect of loadings on the in situ gas permeability was also clarified. It is shown that, although gas permeability through CFRP laminates increases on account of the existence of matrix cracks and tensile loadings, these effects turned out not to be crucial in comparison to the leakage through multi laminar matrix cracks, which is three or four orders higher than the diffusion-controlled permeation. These results suggest that the existence of no less than one intact layer is important for the feasibility of composite propellant tanks. Finally, a diffusion model including the combined effects of damages and loads is applied to the experimental results and a successful characterization of gas permeability is presented. Keywords: LAMINATESMATRIX CRACKSGAS PERMEABILITYDIFFUSIVITYCONTINUUM DAMAGE MECHANICS

Gaseous diffusion

Leakage (economics)

10.1163/1568551042580136

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Citations (20)

Identification of Damage Parameters for Intralaminar Damage Modeling in Laminated Composites Considering Transverse Stress Effects

Open Journal of Composite Materials (2017)

Rehs T. Gerrit Shun Kokubo Tomohiro Yokozeki

The aim of this study is to develop an appropriate modeling methodology for the simulation of intralaminar damage in laminated composites under complex loadings. The intralaminar damages are modeled by stiffness reduction controlled by thermodynamic forces as defined in continuum damage mechanics model proposed by Ladevèze. The original method neglected transverse stress in elementary plies during the tensile tests of [45/?45]mS laminates, resulting in variations of the identified damage parameters of Ladevèze model. This study compared the identified damage parameters considering transverse stress effects with those based on the original method. The effect of transverse stress in the identification process on the damage modeling is discussed, and it is found that one of damage coupling parameters and the damage master curves significantly depend on consideration of transverse stress effects. Finally, it is demonstrated that experimental stiffness degradation is well simulated by the prediction using the identified parameters considering transverse stress effects.

Damage mechanics

10.4236/ojcm.2017.74012

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Citations (3)

Transient Response of a Wing with Corrugated Morphing Control Surfaces

AIAA SCITECH 2022 Forum (2022)

Kensuke Soneda Natsuki Tsushima Tomohiro Yokozeki

In this study, transient aeroelastic behaviors of corrugated morphing wings in a prescribed flight path are investigated. A simulation framework for the wings with corrugated control surfaces is developed. A shell finite element is used to model the composite corrugated morphing wings, and the mechanical properties of corrugations are homogenized to implement in the structural model. An unsteady vortex lattice method (UVLM) is coupled with the structural model to simulate the aeroelastic behaviors of the morphing wings. The prescribed 1-cos plunge motion is forced with corrugated morphing wings with different configurations, and the transient aeroelastic responses are analyzed. The simulation results demonstrate that the morphing structures passively reduce the influences of the plunge motion.

Morphing

Aeroelasticity

Transient (computer programming)

Aileron

10.2514/6.2022-0242

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Citations (0)

Cooling rate-dependent mechanical properties of polyphenylene sulfide (PPS) and carbon fiber reinforced PPS (CF/PPS)

Composites Part A Applied Science and Manufacturing (2022)

Sota Oshima Ryo Higuchi Masaya Kato Shu Minakuchi Tomohiro Yokozeki

Ductility (Earth science)

Brittleness

10.1016/j.compositesa.2022.107250

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Citations (33)