In this paper, we proposed a method for preventing the wrinkling of the facings of a sandwich panel whose outer and inner facings were at different temperatures. By using this method, the wrinkling of the outer facing of a sandwich panel structure, such as a sandwich panel refrigerator box, could be prevented. In order to prevent the facings of the structure from wrinkling, it was necessary to determine the wrinkling strength using a compressive test, and to reduce the thermal stress of the sandwich panel structure to less than the wrinkling strength. It was observed that a sandwich panel structure with slits in the facing reduced the thermal stress. In this study, we used sandwich panel containers to examine whether this proposed method could prevent a sandwich panel from wrinkling.

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In order to establish a strength evaluation method of a high strength material with a notch which has an inclusion, tensile tests of materials, which have various notch radii, and fracture toughness tests for casting high speed steel were performed. The validity of considering that an inclusion is equivalent to a crack and considering the influence of the interference between an inclusion and a notch on the tensile strength using the fracture mechanics was examined. The tensile fracture conditions were evaluated by defining one formula which calculates the stress intensity factor that used the √area parameter model as the tensile fracture conditions K_IB (ρ). As a result of the testing, as for the high strength notch material containing many inclusions, the notch root maximum elastic stress at the time of the fracture varied, and it was shown clearly that the cause was the size scatter of an inclusion. Moreover, a strength evaluation with little scatter was possible by factoring K_IB (ρ) into the fracture conditions. That is, it was clearly shown by considering that an inclusion is equivalent to a crack which is effective when considering the influence that the interference between an inclusion and a notch has on the tensile strength using a stress intensity factor.

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The present paper describes the determination of high strain-rate compressive stress-strain loops for bulk specimens of two different epoxy and methacrylate structural adhesives on the standard split Hopkinson pressure bar with a tapered striker bar. The full compressive stress-strain data including unloading process are obtained over a wide range of strain rates from 10^-3 to 10³/s at room temperature. The effects of strain rate on the initial (secant) modulus, flow stress, dissipation energy and hysteresis loss ratio are studied. The experimental results show that both bulk structural adhesives exhibit highly strain-rate dependent viscoelastic behavior like polymeric materials.

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The combination effects of shot peening (SP) and crack-healing on the contact strength of ceramics were investigated. Si₃N₄/SiC composite ceramics with high crack-healing ability were subjected to SP using zirconium oxide shots with several peening pressures and shot diameters. Then, some of the specimens subjected to SP were heat-treated in air to heal the surface cracks induced by SP. The residual stress, the apparent fracture toughness and the Weibull distribution of the contact strength were investigated. As a result, it was found that the combination of SP and crack-healing is effective for increasing the contact strength and decreasing the scatter of the contact strength.

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This study investigated the mechanical properties of composite using gettou (shell ginger) fiber as reinforcement fabricated from injection molding. Gettou fiber is a natural fiber made from gettou, a subtropical plant that is largely abundant in Okinawa, Japan. We used the stem part of gettou plant and made the gettou fiber by crushing the stem. The composite using gettou fiber contributed to low shrinkage ratio, high bending strength and high flexural modulus. The mechanical strength of composite using long gettou fiber showed higher value than composite using short gettou fiber. Next, because gettou is particularly known for its anti-mold characteristic, we investigated the characteristic in gettou plastic composite. The composite was tested against two molds: aspergillius niger and penicillium funiculosum. The 60% gettou fiber plastic composite was found to satisfy the JISZ2801 criterion. Finally, in order to predict the flexural modulus of composite using gettou fiber by Halpin-Tsai equation, the tensile elastic modulus of single gettou fiber was measured. The tendency of the experimental results of composite using gettou fiber was in good agreement with Halpin-Tsai equation.

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Gels have low frictional properties, permeability and biocompatibility due to high water content. In the last decade, several high-strength gels have been developed, which are promising for extending the application of gels as industrial materials. In this study, ultrahigh ductile gels are proposed by developing Inter Cross-linking Network (ICN), which is the novel internal structure of gels. The ICN gels can achieve more than 67.9% increase in the ductility in comparison with normal poly(N,N-dimethylacrylamide) gels, only by adding a little amount of fiber, hydroxypropyl cellulose, which is known as lyotropic crystalline polymer, while containing 97wt% water.

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