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

In the multilayered structure, the bonding agent can fail; thus imperfect or flexible bonding can appear between the layers when the laminate is subjected to various mechanical and thermal loadings for a long time. Even, the bonding adhesives may either be initially imperfect because of the introduction of small micro defects in the process of manufacture or become deteriorated during its long period of service. It can be modeled as an infinitely thin interface connecting the solids by distributed springs to account for interfacial stiffness reduction due to imperfections. 168