ABSTRACT
This paper presents the results of a series of multi-scale experiments and numerical models concerning the mechanical properties of moso culm functionally graded bamboo structures. On the nano- and microscales, nanoindentation techniques are used to study the local variations in the Young's moduli of moso culm bamboo cross-sections. These are then incorporated into finite element models in which the actual variations in Young's moduli are used to model the deformation and fracture of bamboo during fracture toughness experiments. Similarly, the measured gradations in moduli are incorporated into crack bridging models that predict the toughening observed during resistance curve tests. The implications of the results are discussed for the bio-inspired design of structures that mimic the layered, functionally graded structure of bamboo.
Subject(s)
Bambusa/chemistry , Animals , Bambusa/ultrastructure , Biomechanical Phenomena , Cellulose/ultrastructure , Dogs , Elastic Modulus , Finite Element Analysis , Microscopy, Atomic Force , Models, Biological , Stress, Mechanical , Tensile StrengthABSTRACT
This paper presents the results of a study of the effect of cyclic loading parameters on the performance of piezo crystals. The output power of the crystals was observed to increase with parameters such as the cyclic frequency and the dynamic load range. However, the output power also decreased with increasing mean load. The efficiency of the crystal was calculated based on the mechanical energy applied to the piezo crystal. The ratio of the electrical output to mechanical energy input was taken as the efficiency of the crystal. This ratio was seen to increase with the cycling frequency, and also with the dynamic load range. However, increasing mean load caused the efficiency to drop significantly. The implications of the results are discussed for possible applications implanted bioMEMS and microelectronics systems.
