Study On Two-Dimensional Solid/Solid Phononic Crystal With In-Situ Tunable Band Gaps

Phononic crystal with tunable band-gap is a novel direction in the study of the phononic crystal. In this paper, the new concept of solid/solid two-dimensional phononic crystal with tunable band-gap using the change of the elastic modulus before and after the martensite phase change of the shape memory alloy was put forward.Enumerate energy band structure of the XY mode and the Z mode of the SMA/epoxy resin system in the two different state. Numerical results showed that the change of the lowest complete band gaps composed of the change of the width and the center frequency of the band gap, in some special structure parameter, it coulde take an similar effect of "on-off, that is, there was no band gap in the martensite state, but after the phase change, the band gap appeared, accordingly confined the pass of the sound wave in this range of frequency. For the same phononic crystal, the change trend of the lowest complete band gaps in the XY mode and the Z mode was similitude: the frequency of the band gap in austenite state was lower than which in martensite state, the width of the band gap maybe increase or decrease with the differences of the filling fraction and the lattice structure.The influence of the effect of the filling fraction on the band gap tuning was studied. For the square lattice and the triangular lattice ,the filling fraction take a more clear effect on the band gap tuning. At the lower filling fraction, the change degree of the center frequency was greater than the width of the band gap, but the instance was opposite at the higher filling fraction. For the hexagonal lattice, the change rule was opposite to the square lattice and the triangular lattice, with the increase of the filling fraction, the change degree of the band gap width raised, but the rising wasn't too high, and the change degree was negative; however, the change degree of the center frequency is greater.The influence of the effect of the crystal lattice on the band gap tuning was discussed. The results showed that the effect of the crystal lattice on the band gap tuning is great. For the square lattice and triangular lattice ,at f>40 %, the band gap width in austenite state was higher than which in martensite state, for the hexagonal lattice, at any filling fraction, the band gap width in austenite state was lower than which in martensite state. For the tuning on the center frequency of the band gap, the result is opposite, in hexagonal lattice ,the change degree is greatest,outwent the other two lattice structure.Compared the change degrees of the band gap width and the center frequency with the cross section were circle, square and the square rotated 45 ° 。 The result showed only tiny difference, which illuminated that the geometry of the inclusion took tiny effect on band gap tuning.From a great deal of analyze result, we can draw a conclusion that the parameter led to the better effect on center frequency was corresponding to the worse effect on band gap width. Accordingly, in order to achieve the better effect in the two aspect, we should consider integratedly, and select the suitable parameter.The feasibility of the tunable band gap was Confirm by experiment. Comparing the testing result of the same phononid crystal at the room template and the high template, we discovered that the energy band structure before and after the martensite phase changed, the band gap width in austenite state was wider than which in martensite state, and the center frequency moved to the low frequency. All of these is the same as the Numerical results. Which showed that realizing the tunable band gap by changing the template was feasible.Comparing the testing result and the numerical results, we discovered there were obvious differences between them. Consequently, we analyzed the cause. The differences can be decreased by advancing preparation technics, rectifying the material characteristic parameter, which confessed the improving method for the further work.