Analysis of the Effects of Fiber Gradient Distribution on the Mechanical Properties of Moso Bamboo

Bamboo is a fiber-reinforced bio-composite with superior structural behavior. For the purpose of analyzing the correlations between the mechanical properties of bamboo and fiber volume fraction, tensile tests were performed on bamboo test specimen, and the corresponding volume fractions of fiber and parenchymatous ground tissue were measured. Linear and curvilinear regressions were done from tested data of elastic modulus, tensile strength and volume fractions of fiber. The results display that there is an obvious correlation between bamboo tensile properties and fiber volume fraction. In order to analyze the effects of fiber gradient distribution on bamboo structural behavior, models composed of fiber and parenchymatous tissue were built based on different fiber distribution for comparative analysis. The analysis results show that the maximum deformation of 4 layers model is 3.86% less than 1 layer model, and the maximum deformation of 8 layers model is 8.87% less than 4 layers model. In the part of maximum axial stress, the maximum axial stress of 4 layers model is 3.27% less than 1 layer model, and the maximum axial stress of 8 layers model is 8.90% less than 4 layers model. Conclusion can be drawn from the comparison that the strength and stiffness of the model appear to be growing with the degree of fiber gradient distribution deepening from 1 layer model to 4 layers model, and 4 layers model to 8 layers model.It can be concluded that the mechanical properties of bamboo structure are significantly improved because of fiber gradient distribution.

The Optimum Stepped-Pipe String With Vibration Absorbers for Mining Manganese Nodules, to Reduce Its Maximum Axial Stress

In order to reduce the maximum axial stress produced in the pipe string for mining manganese nodules from deep-sea floors by a pump-lift system, the string is assumed to be a two-stepped pipe string with larger diameter in the upper part. Moreover, a buffer and two pump-modules attached to the string are assumed to be equipped with a vibration absorber. Then, the longitudinal vibration and axial stress caused in the string by the heave-motion of the mining ship are analyzed theoretically for practical cases. The result shows that the maximum axial stress in the optimum stepped pipe-string with the buffer having the optimum vibration absorber is found to be smaller by about 42 percent than the one produced in the uniform pipe string with the same mass and no vibration absorbers.