Flexural rigidity with respect to the frequency for two different interface conditions. For the blue curve, the simulation has been done with B = 0 m.Pa⁻¹, which is a perfect interface structure. The red dotted line has been done with the same material but with imperfect interfaces with B = 10e−9 m.Pa⁻¹ = 1e−8 m.Pa⁻¹. The material properties for this example are gathered in Table 1.