| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 105 === In this thesis, the wave propagation in phononic crystal composed of auxetic star-shaped
honeycomb matrix with negative Poisson’s ratio is presented. Two types of inclusions with
circular and rectangular cross sections are considered. The band structures of the phononic
crystals are obtained by the finite element method. The band structure of the phononic crystal
is affected significant by the auxeticity of the star-shaped honeycomb. Some other interesting
findings are also presented, such as the negative refraction and the self-collimation. The
present study demonstrates the potential applications of the star-shaped honeycomb in
phononic crystals, such as vibration isolation and the elastic waveguide. The results reveal
that the phononic crystals composed of auxetic materials can have a great potential for the
design of novel acoustic devices. Furthermore, the low frequency band gap of local resonant
phononic crystals with auxetic coating material are also investigated. Low frequency waves,
in the range 3–15 Hz for earthquakes and up to hundreds of Hz for vibrations generated by
machine tool, cause a large amount of damage or inconvenience. The first band gap of local
resonant phononic crystals with auxetic coating material can applied for this region of
frequency.
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