The aviation industry is constantly pursuing enhancing passenger comfort and safety, with noise reduction within aircraft cabins being a critical area of focus. Traditional soundproofing methods, often involving the addition of heavy and voluminous materials, conflict with the industry's goal of maintaining lightweight aircraft and minimising fuel consumption. Previous research suggests that Helmholtz resonators offer a promising approach to noise control. Their simple structure, consisting of an enclosed volume connected to the external environment through an aperture, allows for customisable and scalable noise control applications.

The thesis presents exploratory research into integrating Helmholtz resonator-based metamaterials into lightweight composite acoustic sandwich panels for aircraft cabins. First, the stiffness of the resonator's enclosure is investigated, followed by determining the effects of placing the inlet within the resonance chamber. Next, the implications of creating resonators for single-layer acoustic sandwich panels are studied. Finally, three reinforcement fibres are investigated for acoustic suitability: fibreglass, carbon fibre and flax fibre. The study concludes with a weight comparison between the developed metamaterial sandwich panel and commercial designs.

The findings reveal that the lay-up of the face sheets significantly affects sound absorption. Introducing non-resonant volumes between the metamaterial's unit cells is the most effective method to prevent interference between the resonators. The resonator's inlet disrupts the stress flow in one of the face sheets, leading to locally increased stress values. The need for specific acoustic properties requires core cell sizes larger than those typically used in standard cabin panels, compromising the stability of the face sheets. Support columns are proposed as a solution, lessening the impact on stability. The thesis proves that lightweight composite single-layer acoustic panels are achievable by incorporating Helmtolhtz resonator-based phononic metamaterials.

Piezoelectric metamaterials, recognized for their remarkable electromechanical coupling, have garnered significant attention for their ability to generate artificial nonzero piezoelectric coefficients beyond those of natural ceramics. Despite being a relatively nascent field, research in piezoelectric metamaterials is expanding rapidly, driven by their potential applications in dynamic environments, including vibration-dominated systems. This study advances understanding in this field by focusing on the wave dispersion characteristics of 2D piezoelectric truss metamaterials.

Using a multiphysics finite element framework based on Euler-Bernoulli beam theory, we develop a robust model to capture 3D deformation and apply the Wave Finite Element Method with Bloch boundary conditions to analyze dispersion relations. Mode identification is performed to investigate the effects of piezoelectricity on both in-plane and out-of-plane wave modes. Two distinct lattice configurations—rectangular with varying stretch ratios and hexagonal with different internal angles—are systematically analyzed to elucidate their wave propagation behaviour.

The findings reveal that piezoelectricity significantly impacts in-plane modes by reducing group velocity and modifying bandgap structures. Conversely, out-of-plane modes remain unaffected. Notably, piezoelectricity strongly suppresses energy flow in the direction of poling, enabling directional wave control and facilitating wave beaming phenomena. These results highlight the potential of piezoelectric metamaterials in achieving tunable wave propagation and directional energy flow.

To the best of our knowledge, this study marks the first comprehensive investigation into wave dispersion in piezoelectric truss metamaterials. The developed framework, rigorously validated against established results for purely mechanical metamaterials, demonstrates robustness and reliability. By advancing the theoretical modeling of piezoelectric truss lattices, this work bridges the gap between foundational research and transformative applications, including energy harvesting, wave control, and sensing technologies. These findings establish a solid platform for future exploration of 3D piezoelectric truss lattices and the strategic use of dynamic stimuli to engineer tunable bandgap materials.