Study of imperfect bonding effects on sound transmission loss through functionally graded laminated sandwich cylindrical shells

Abstract

Effects of imperfect bonding on sound transmission across a double-walled cylinder with FGM-core are studied by using the three-dimensional theory of elasticity. Aluminum and zirconia are inner and outer shells respectively, whereas the FGM-core is sandwiched between these layers. A very thin adhesive epoxy interlayer was applied in order to bond the adjacent layers. The imperfect bonding (adhesive epoxy interlayer) is modeled by a linear spring model. Infinite values of stiffness of linear spring reveal that there are no interfaces between the adjacent layers. However, the interface tractions do not exist and the layers are completely deboned from each other due to zero values of these parameters. The linear spring model is incorporated into the global transfer matrix with the aid of suitable transfer matrices. The proposed model is used to calculate the effects of imperfect bonding on TL of multi-layered cylinder which excited by an external plane wave. The obtained results are compared with those of other researches recently published in the literature. Excellent agreement is observed for high stiffness of adhesive bond. The results have also illustrated the fact that the existence of imperfect interfaces leads to the enhancement of the TL of sandwich cylindrical shell. Moreover, low stiffness of interlaminar adhesive bonding has more positive effect on the TL enhancement, particularly in high frequency range. Finally, it can be concluded that at high frequencies the spring layer model with low stiffness cannot transmit the waves because of more fluctuations.