Topology optimization of pentamode metamaterials for underwater acoustics

TL;DR

This paper introduces an automated topology optimization framework for designing pentamode metamaterials with tailored acoustic properties for underwater applications, enabling precise control and manufacturability of complex microstructures.

Contribution

It develops a novel optimization approach combining homogenization, adjoint sensitivity analysis, and the Virtual Temperature Method to design fluid-like acoustic metamaterials without predefined geometries.

Findings

Successfully designed a L"uneburg lens for underwater acoustics.

Created an acoustic invisibility cloak demonstrating cloaking performance.

Validated designs through comprehensive acoustic-elastic simulations.

Abstract

This study presents an automated topology optimization framework for designing pentamode acoustic metamaterials. It provides precise control over the material effective acoustic properties while minimizing the shear modulus to achieve fluid-like behavior. The approach combines low-frequency homogenization for accurate property evaluation and the adjoint method for efficient sensitivity analysis. The Virtual Temperature Method (VTM) ensures structural connectivity and manufacturability, addressing the typical challenges of low-stiffness, high-mass-density microstructures. The framework is demonstrated through the design of a L\"uneburg lens and an acoustic invisibility cloak for underwater applications. Acoustic-elastic simulations validate the performance of both the unit cells and the complete devices. This method eliminates the need for predefined geometries, offering a flexible, reliable, and scalable alternative to conventional parametric optimization. It provides a powerful tool for the automated design of complex, anisotropic, pentamode metamaterials.