Phd in ENGINEERING AND APPLIED SCIENCE FOR ENERGY
AND INDUSTRY

Thesis title: Biphasic Mechanical Metamaterials for sound and vibration mitigation

The manipulation of elastic and acoustic wave propagation in structured media has attracted significant attention in the development of advanced noise and vibration control technologies. Conventional homogeneous and periodic structures offer limited control over broadband attenuation, particularly when multiple types of waves propagate simultaneously in solid and fluid domains. Metamaterials, through engineered periodicity and material contrast, enable the formation of bandgaps that can inhibit wave transmission over targeted frequency ranges. In this thesis, the design, modeling, and analysis of biphasic mechanical metamaterials for simultaneous sound and vibration mitigation are investigated. The underlying wave physics in biphasic media is investigated through a computational framework based on the Semi‑Analytical Finite Element (SAFE) method, addressing the dispersion eigenproblem and facilitating the analysis of topology dependent dispersion characteristics. Parametric studies reveal the role of material properties, phase distribution, and structural geometry in bandgap tuning. Numerical forced response and transmission evaluations confirm the attenuation capabilities of finite array biphasic configurations. Extending the approach to three‑dimensional architectures, preliminary numerical simulations validate the dynamic predictions. These results underscore the potential of such metamaterials for simultaneous wave mitigation solutions. The specific contributions of this thesis are: 1. Dispersion analysis methodology: Development of a computational method for dispersion eigenproblem analysis, employing the SAFE approach to determine band structures in biphasic periodic media. 2. Bandgap tuning strategy: Incorporate geometrical topology optimization, inter‑cellular intra‑phase connectivity control, and phase mismatch engineering to tailor dispersion characteristics. 3. Hybrid modes classification: Integration of multi‑physics numerical modeling, including the introduction of energy‑based polarization factors for rigorous characterization and classification of wave modes. 4. Finite array metafilter design and performance assessment: Realization of a broadband wave attenuation metafilter, demonstrating an effective biphasic configuration with quantitative transmission coefficient analysis across targeted frequency ranges.