In recent years, the promising patch repair method using FRP composite patches bonded to the damaged components of high speed transportation systems has received much attention. In this paper, the patching efficiency in cracked structural panels repaired with a bonded FRP composite patch containing a piezoelectric fiber composite actuator layer is investigated. A two-dimensional finite element method is used to obtain stress intensity factors at a crack tip. The structural panel and composite patch are modeled as layers composed of Mindlin plate elements, while the adhesive layer is modeled as a thin elastic one. The stress intensity factors are calculated using the modified crack closure method. The effects of location of piezoelectric fiber composite actuator layer, size and shape of FRP composite patch, and stacking number of actuators on the patching efficiency are examined. We also discuss the effect of disbond area on the patching efficiency.
The base flow field of a vertical landing rocket in ground effect is numerically studied to clarify the mechanism of downward force acting on the body. Two characteristic patterns in the pressure distribution on the base surface are successfully captured as observed in the experiments. When the distance between the base and the ground surface is small, vorticies generated in the shear layer of the jet boundary interact with both the ground and base surfaces. The base pressure near the axis of the base is significantly reduced and large downward force appears due to vortical structure in the base region. When the distance is large, the vorticies are convected along the ground surface and the base pressure near the edge of the vehicle base is reduced due to suction of the ambient air. The numerical results indicate that unsteady motion of such vortices plays an important role in formation of the flow patterns described above.
Main-lobe energy transmission using an optical phased array is proposed. Effects of spatial and temporal coherence of rectangular-symmetric laser arrays on energy transmission performance are evaluated in terms of the main-lobe beam quality factor and the main-lobe energy transmission efficiency. As a result, the efficiency is found independent of the number of laser elements and their spectral broadening, and sensitive to the aperture fill factor. The main-lobe beam quality factor remains constant for any cases.
Structural health monitoring of fatigue-cracked aircraft structural panels repaired with bonded patches for extending the service life of aging aircraft has received wide attention. In this paper, we deal with an identification for the locations and shapes of crack and disbond fronts in aircraft structural panels repaired with bonded patches. The identification is performed by minimizing the residual norm between the measured in-plane strain range at multiple points on a free surface of patches and the calculated in-plane strain range. The validity of the identification is verified by experiments.
Hybrid-ramjet is proposed in this paper. It is the combined engine of a liquid fuel ramjet and a ducted rocket. The high Isp performance and the wide fuel flow control range of a liquid fuel ramjet and the high combustion stability of a ducted rocket are expected. Theoretical calculations of the hybrid-ramjet which has same mass solid fuel and liquid fuel, were conducted. The results shows 50% higher Isp and twice fuel control range compared with a ducted rocket.
When the body is moving with an accelerating motion, we must take the virtual mass (added mass) into account. The mapping function is generally used to calculate the virtual mass, while it is so hard to find an appropriate mapping function for the requested any shape body. Simplified method is presented, in which a complex logarithmic function is introduced discretely to describe any shape body and the disturbance of flow expressing the kinetic energy induced by the accelerated body is calculated by it. After expanding the function around the origin, the virtual mass for any shape body is calculated by introducing the “equivalent radius.” Results show the good agreement with the analytical solution.