Study on the band gaps of phononic crystal pipes with alternating materials in the radial and axial directions

- Several new complex cells are designed.
- The new complex cells bring different band structure characteristics. The suggestion given by the Bragg-type band gap mechanism are corrected and improved.
- The new Bragg-type phononic crystal pipes with a same lattice constant obtain a lower frequency band gap or widen the low-frequency band gap.

Low-frequency vibration control is a key technology in the vibration control of pipe systems. The existing related research on band gap mechanisms suggests that gigantic structures are required for the Bragg-type band gaps to control low-frequency vibration. Thus, the application of Bragg-type phononic crystal pipe is greatly restricted. However, the suggestion given by the existing Bragg-type band gap mechanisms is based on simple cell structure and material composition. The cell structures of Bragg-type phononic crystal pipes are also simple and the potential action of the cell has not been fully excavated at present. In this paper, several new cells with relatively complex structure are designed to study the influence on the Bragg-type band gap characteristics. Band structures of the Bragg-type phononic crystal pipes with new cells are calculated via a combination of periodic structure theory and finite element method. Compared to the classical phononic crystal pipe, when a same lattice constant is adopted, the phononic crystal pipes with new cells obtain lower frequency band gaps or widen the low-frequency band gaps.