The Influence Of Interface Effects On The Band Structures In 2D Phononic Crystals

Due to their particular properties and the prospective application,more and more attention has been paid to the phononic crystals.As one of the composite materials composed by two or more periodically arranged elastic materials,the total area of the matrix-scatter interface cannot be ignored.They must have a great influence on the performance of the phononic crystals.Ordinarily,weld interface is assumed in the theoretical and numerical discussion.But due to all kinds of reasons,defects may exist at the interface.Moreover,some specific interface may be required in the real applications.However,less attention has been paid to the effects of the interfaces.In this dissertation,the influence of different contact interfaces(weld interface,the radial contact and the tangential contact interface) on the x-y mode waves in 2D phononic crystals has been investigated by using FDTD method.Firstly,for epoxy/Al system with weld interface,the effect of the scatter shapes(square,circular,or triangular) and the filling fraction on the dispersion properties of 2D phononic crystals are discussed.Then,by using radial or tangential contact interface condition,the effect of the interface stiffness coefficient and the filling fraction on the band structures is analyzed.The main results are as follows:1.If the interface is weld contact,the scatter shapes have influence on the dispersion properties of the solid-solid 2D phononic crystals.Along with the increasing of the filling fraction,the central frequency of PBG shows monotonic increasing.But band gap width firstly grows and then falls down when the filling fraction is larger than a critical value(see,f=0.6);2.If the interface is radial contact,the band gap width shows monotonic increase as the contact stiffness coefficient is increased.At the same time,the central ratio is also increased.It is seen that the larger the filling fraction is,the more easily the band gap forms.3.When the interface is tangential contact,no PBG would be open,but directional gaps may appear along the directionsΓX and XM.It should be noticed,at the directionΓM,no directional forms.