Kazuya Okubo

Fatigue Notch Sensitivity of Glass Woven Fabric Composites Having a Circular Hole under Tension/Torsion Biaxial Loading

Fatigue notch sensitivity of woven fabric composites having a circular hole under tension/torsion biaxial loading was investigated. In-phase (proportional) biaxial stress was applied to tubular specimens. A fatigue notch factor was used to evaluate the fatigue notch sensitivity. The experimental results revealed that the fatigue notch factor was approximately linear with respect to a parameter; cos (tan- ce) for any fatigue life (a is biaxiality ratio of combined stress). The fatigue notch factor decreased with an increase in fatigue life in the case where the shear stress component was relatively small. However, in the case where the shear stress component was large, it increased with an increase in fatigue life. Under pure torsion loading, fatigue damage did not progress along the principal axis. It grew along both longitudinal and transverse fiber bundles. An empirical equation which can easily predict the fatigue notch factor at any arbitrary fatigue life under biaxial loading was proposed. Unknown variables in this equation are determined by fatigue tests under uniaxial tensile and pure torsion loadings.

Evaluation of oil-leakage of multi-layered resin-hose clamped with metal nipple and sleeve

The purpose of this study is to investigate the path of occurred oil-leakage of multi-layered resin-hose as one of multifunctional materials around the caulked joint with a metal nipple and sleeve when excessive cyclic internal pressure was applied onto the hose. Equivalent cyclic axial tensile force was substitutively applied to the hose, where same degree of normal stress was produced in longitudinal direction. Excessive 3 and 5 times of the standard load was applied to the hose. Cyclic loading was paused at every 1000 and 10000 cycles and then designed internal pressure was applied to the hose by a hand-operated pump with water in order to check whether the leakage was occurred around the joint and surface of the hose for safety evaluation. Cyclic fatigue life was defined as the number of loading cycles in which the leakage and the initial damage which was the passage of the ultrasonic wave was observed on the cyclic test. Test results showed the fatigue life at which leakage of water was observed was increased 20 times in case of K=3 compared to that in case of K=5. The cycles of initial damage detected by the ultrasonic wave were passed was increased 3.3 times in case of K=3 compared to that in case of K=5. The fluorescent agent penetrated from the core layer of resin hose to the reinforcement layer in which a half cross section along longitudinal direction in failed specimens was observed after the leak test. The original specimens had the gap between the resin-hose and the nipple and then the gap extended and connected during fatigue cyclic. In this study, it was observed that oil was leaked through narrow gap between the nipple and core layer of resin hose.

Effects of heat treatment on the mechanical properties of kenaf fiber

Natural fibers are utilized in various ways. One specific application of it, is in the field natural fiber composite (NFC). Considerable amount of researches are conducted in this field due to rising concerns in the harmful effects of synthetic materials to the environment. Additionally, these researches are done in order to overcome the drawbacks which limit the wide use of natural fiber. A way to improve NFC is to look into the reinforcing component (natural fiber). Treatments, which are classified as mechanical or chemical in nature, can be done in order to improve the performance of the natural fiber. The aim of this study is to assess the effects of heat treatment in the mechanical properties of kenaf fiber. In addition, the response of mechanical properties after exposure to high moisture environment of heat-treated kenaf fibers was observed. Heat treatment was done for one hour with the following heating temperatures: 140, 160, 180, and 200 °C. X-ray diffraction analysis was done to calculate the c...