  Marine shells are designed by nature to ensure mechanical protection from
predators and shelter for mollusks living inside them. A large amount of work
has been done to study the multiscale mechanical properties of their complex
microstructure and to draw inspiration for the design of impact-resistant
biomimetic materials. Less is known regarding the dynamic behavior related to
their structure at multiple scales. Here, we present a combined experimental
and numerical study of the shells of two different species of gastropod sea
snail belonging to the Turritellidae family, featuring a peculiar helicoconic
shape with hierarchical spiral elements. The proposed procedure involves the
use of micro-Computed Tomography scans for the accurate determination of
geometry, Atomic Force Microscopy and Nanoindentation to evaluate local
mechanical properties, surface morphology and heterogeneity, as well as
Resonant Ultrasound Spectroscopy coupled with Finite Element Analysis
simulations to determine global modal behavior. Results indicate that the
specific features of the considered shells, in particular their helicoconic and
hierarchical structure, can also be linked to their vibration attenuation
behavior. Moreover, the proposed investigation method can be extended to the
study of other natural systems, to determine their structure-related dynamic
properties, ultimately aiding the design of bioinspired metamaterials and of
structures with advanced vibration control.
