Intelligent functionally graded material: Bamboo

Since the shape and ingenious construction of biological hard tissues are the result of a continuous process of optimization, their basic characteristics such as microstructures, functions, and modelling systems fascinate the designers of engineering structures. Through the study of functionally graded materials, we hope to develop new superior material/structure concepts by using or modifying the construction of living organisms. The ingenious construction of bamboo was studied herein to help in the understanding of the principles and the design processes found in biological materials which are multi-phased and functionally graded composites. It was found that the ability of a bamboo cell to generate electrical signals when stressed was an apparently similar function to that of the piezoelectric effect in bone which is stressed. It is also suggested in this paper that the electrical properties play an important role in the modelling/remodelling of the skeletal system in biological hard tissues. It is concluded that a bamboo structure is designed to have uniform strength at all positions in both the radial direction on the transverse section and the lengthwise direction, and that bamboo is a self-optimizing graded structure constructed with a cell-based sensing system for external mechanical stimuli.