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Volume 41 (2015)
- Issue 5 Pages 149-
- Issue 4 Pages 106-
- Issue 3 Pages 75-
- Issue 2 Pages 47-
- Issue 1 Pages 9-
Volume 41, Issue 5
Displaying 1-4 of 4 articles from this issue
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Research paper
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Ryuji NOROTA, Yoshiyasu HIRANO, Ryosuke MATSUZAKI, Toshio OGASAWARA2015 Volume 41 Issue 5 Pages 149-158
Published: 2015
Released on J-STAGE: November 02, 2016
JOURNAL FREE ACCESSThis study examines detailed damage mechanisms of CFRP laminate subjected to impulse lightning current by conducting experiment and numerical simulations. It is concluded that damage mechanisms of surface resin deterioration which cannot be simulated by past numerical studies can be explained by cross interaction effect of material insulation breakdown and directional creeping discharge due to strong electrical orthotropy of CFRP. High-speed camera observation shows rapid resin evaporation developed along surface fiber transverse direction resulting in surface resin deterioration damage. In order to explain this behavior, thermal–electrical coupling FEM analysis considering temperature dependent electrical property change due to resin sublimation and insulation breakdown was conducted. The result shows insulation breakdown strongly affects temperature distribution inside specimen due to Joel heating; on the other, temperature distribution in thickness direction was excessive than expected by experimental result. This fact indicates that part of applied impulse current was separated as creeping discharge and did not flow into specimen. To examine this phenomenon, electromagnetic field analysis with FDTD was conducted. The result shows current of creeping discharge is strongly affected and results in directional creeping discharge in transverse direction to fiber because of generated magnetic field due to strong electrical orthotropy of CFRP.View full abstractDownload PDF (2800K) -
Kento SHIMODE, Tomohiro YOKOZEKI, Takahira AOKI, Keita TERASHIMA, Toru ...2015 Volume 41 Issue 5 Pages 159-167
Published: 2015
Released on J-STAGE: November 02, 2016
JOURNAL FREE ACCESSAnisogrid lattice structure, consisting of helical and hoop ribs intersecting each other in a regular pattern, is considered to be a superior candidate as the lightweight and low-cost aerospace structure such as payload attachment adapter and inter-stage structure of launch vehicles. It is also expected that lattice structure has high wave attenuation and vibration damping properties owing to the nodal structure, which additionally motivates us to apply the lattice structure to the launch vehicle structures to reduce the high-level shock loads during the launch and the separation of the spacecraft. In this study, shock propagation behavior of composite lattice structures is experimentally evaluated. Transient responses of CFRP lattice structure by the impact are measured by using accelerometers. The superior wave attenuation property of the composite lattice structures is demonstrated by the comparison with several other structures in the previous references. Moreover, a simplified analytical method for the prediction of the shock responses of lattice structures is presented in this paper. The shock attenuation characteristics of CFRP lattice structure are explained by the analytical predictions.View full abstractDownload PDF (2455K) -
Shoma NIWA, Kazunori TAKAGAKI, Shu MINAKUCHI, Nobuo TAKEDA2015 Volume 41 Issue 5 Pages 168-175
Published: 2015
Released on J-STAGE: November 02, 2016
JOURNAL FREE ACCESSProcess-induced residual strain causes unexpected shape distortion, leading to premature failure and high manufacturing cost. Cure process simulation is an effective way to optimize the cure process in a reasonable manner. Accurate material properties (i.e., shrinkage strain and elastic modulus change during curing) are vital for high-fidelity simulations. This study first evaluated chemical cure shrinkage of carbon fiber reinforced plastic (CFRP) laminates with interlaminar-resin layers. Transverse and through-thickness strain of a typical UD laminate and a unique UD laminate, whose interlaminar-resin layers were aligned in the through-thickness direction, were measured by fiber Bragg grating (FBG) sensors to clarify the effect of the interlaminar-resin layers on the cure shrinkage. Next, the cure process was simulated by fully integrating the in-situ strain measurement. We embedded two FBG sensors (i.e., short tail FBG and long tail FBG) into a UD laminate. The material properties were then determined based on the different responses of the two FBG sensors due to the shear-lag effect at the edge of the sensors. Finally, cure process simulation was carried out and compared with the experiment. The simulated strain agreed well with the measured value, confirming the validity of the proposed approach.View full abstractDownload PDF (2909K) -
Yasuhiro SHIMADA, Ryosuke MATSUZAKI, Akiyuki TAKAHASHI2015 Volume 41 Issue 5 Pages 176-184
Published: 2015
Released on J-STAGE: November 02, 2016
JOURNAL FREE ACCESSThe present study investigated a numerical simulation of molding-defect formation during resin transfer molding using boundary element method and line dynamics. The proposed method enables to simulate small molding defects by increasing the node for required position during time evolution; thereby, the method computes high-resolution flow front without being affected by the initial mesh geometry. The method was applied to the radial injection RTM with single inlet, and it was confirmed by comparison with theoretical value based on Darcy’s law that the flow advancement was computed with high accuracy. In addition, the method was also applied to the flow advancement for inclusion problem with cylinder, and four-point injection problem. The simulated void formation and shrinkage, and weld line agreed with the results in references. Finally, the method was compared with experiments by using two-point injection problem. The computed configuration of the flow front and weld line agreed well with the experimental results.View full abstractDownload PDF (4483K)
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