[SY-H9] Modelling and 3D Printing Kelvin Cell Acoustic Metamaterial
Anisotropic metamaterial properties could be reached from design geometric structures. It can consist of functionality unit cells including microscale complex geometries to control the wave propagation. Structures based on regular Kelvin cells were selected and aims for design innovative devices to mitigate the civil aviation noise.
Inspired by the ultrahigh resolution 3D printer technology, manually controlled cell geometry would be possible. Polymer material was used in 3D printer. Samples with 0.1 mm diameter beam element kelvin cell model was printed in our lab and shows certain acoustic properties to reduce noise.
To understand the fully anisotropic metamaterial behavior, inverse estimation method was applied to get the 21 stiffness parameters in Hooke’s matrix. Optimization method was developed to design Kelvin cell structure to target noise reduction functions. It consists in numerically fitting a solid anisotropic model on a set of transfer functions extracted from Kelvin model. The estimated stiffness matrix is updated after each iteration until converge to an optimal solution. Feedbacks from modelling were used to control the geometry and material parameters in design. It would also be used to investigate modified noise scattering patterns in acoustic metamaterial. 3D printed samples would also be tested in wind tunnel to verify the numerical analysis.
Additional sub-elements, e.g., polymer microparticles could also be imbedded in the cells to increase viscous/damping loss and widen frequency bands. The frequency band could be adjusted according to the application by changing the geometry. Most of the sound could be decreased in the selected frequencies. If titanium was used in 3D printer, the cell size of the metamaterial would be much smaller that would increase acoustic properties too. The sound absorbing capacity of the titanium metamaterials, together with their strength and weather resistance, would also make them attractive candidates in noise and vibration control of aircrafts.
This work is a part of European project AERIALIST (AdvancEd aiRcraft-noIse-AILeviation devIceS using meTamaterials), which aims at the disclosure of the potential of metamaterials to envisage innovative devices for the mitigation of the civil aviation noise (https://www.aerialist-project.eu).
Inspired by the ultrahigh resolution 3D printer technology, manually controlled cell geometry would be possible. Polymer material was used in 3D printer. Samples with 0.1 mm diameter beam element kelvin cell model was printed in our lab and shows certain acoustic properties to reduce noise.
To understand the fully anisotropic metamaterial behavior, inverse estimation method was applied to get the 21 stiffness parameters in Hooke’s matrix. Optimization method was developed to design Kelvin cell structure to target noise reduction functions. It consists in numerically fitting a solid anisotropic model on a set of transfer functions extracted from Kelvin model. The estimated stiffness matrix is updated after each iteration until converge to an optimal solution. Feedbacks from modelling were used to control the geometry and material parameters in design. It would also be used to investigate modified noise scattering patterns in acoustic metamaterial. 3D printed samples would also be tested in wind tunnel to verify the numerical analysis.
Additional sub-elements, e.g., polymer microparticles could also be imbedded in the cells to increase viscous/damping loss and widen frequency bands. The frequency band could be adjusted according to the application by changing the geometry. Most of the sound could be decreased in the selected frequencies. If titanium was used in 3D printer, the cell size of the metamaterial would be much smaller that would increase acoustic properties too. The sound absorbing capacity of the titanium metamaterials, together with their strength and weather resistance, would also make them attractive candidates in noise and vibration control of aircrafts.
This work is a part of European project AERIALIST (AdvancEd aiRcraft-noIse-AILeviation devIceS using meTamaterials), which aims at the disclosure of the potential of metamaterials to envisage innovative devices for the mitigation of the civil aviation noise (https://www.aerialist-project.eu).