Final Report Summary - MECHMAM (Multiscale Extended Computational Homogenization for the Mechanical design of Advanced Materials)
The project MECHMAM addresses a fundamental challenge in bridging scales in the mechanics of engineering materials, requiring a breakthrough in lifting the existing limits in terms of scale separation. The projects developed a novel extended multiscale homogenization framework, in order to realize its objectives. The prime application field of the project are advanced mechanical and dynamical metamaterials, exploiting complex interactions between the scales involved.
Mechanical materials have the extraordinary characteristic that their mechanical properties can be switched, depending on the local microstructural pattern (or conformation) triggered. For engineering applications, it is computationally impossible to incorporate the microstructure of mechanical metamaterials in full-scale computations. To remedy this, MECHMAM developed a novel micromorphic homogenization framework, which employs different micromorphic modes, representing the microstructural conformations. The key novelty is the direct incorporation of the microstructural conformations (or modes) in the kinematical description of the materials at the macro-scale.
The second breakthrough realized, concerns the multiscale model for acoustic metamaterials (AM). These materials have specially fabricated microstructures capable of advanced manipulation of sound waves such as band-pass filtering, redirection, channelling, multiplexing etc. that is otherwise impossible to achieve using ordinary materials. Within MECHMAM a novel and versatile numerical multi-scale technique has been developed for the simulation and analysis of complex elasto-dynamics of acoustic metamaterials. An extended homogenization technique for modelling materials with local resonances is proposed, resulting in an accurate description of the effective macroscopic continuum in a low frequency regime. The resulting equations constitute an enriched (micromorphic) continuum in which additional kinematic degrees of freedom emerge to account for local resonance effects which would otherwise be absent in a classical continuum. This result enables the development of a multiscale semi-analytical analysis technique for locally resonant acoustic metamaterials, allowing for fast transmission and dispersion analyses for arbitrary and complex micro-structure designs. The model has also been generalized in the project in order to account for both Bragg scattering and local resonance effects.
The third break-through is the development of the ‘metafoam’ concept. Metafoams are based on the combination of the working principle of acoustic foams (relying on visco-thermal energy dissipation due to the foam cell structure), combined with the local resonance phenomenon, originating from implanted small masses (smaller than the cell structure). While the former mechanism is effective in the mid- and high-frequency acoustic regimes, the latter can significantly enhance the low-frequency sound protection. Within MECHMAM, the metafoam concept has been introduced, and theoretically and numerically assessed and demonstrated. Upscaling from lab samples to mass production routes should be at reach in the near future.
Other important scientific achievements in the project are:
• identification and extraction of micro-fluctuation fields in heterogeneous strain or displacements fields, which is relevant for damaging microstructures or patterning metamaterials
• a novel global digital imaging correlation technique, which identifies extracts pre-defined fluctuation patterns of experimental images (including imaging artefacts).
• a novel model reduction approach, relying on the use of wavelets for approximating the mechanical fields, allowing for direct error control
• a full-field kinematical experimental analysis of meta-structural cells with embedded resonators
Mechanical materials have the extraordinary characteristic that their mechanical properties can be switched, depending on the local microstructural pattern (or conformation) triggered. For engineering applications, it is computationally impossible to incorporate the microstructure of mechanical metamaterials in full-scale computations. To remedy this, MECHMAM developed a novel micromorphic homogenization framework, which employs different micromorphic modes, representing the microstructural conformations. The key novelty is the direct incorporation of the microstructural conformations (or modes) in the kinematical description of the materials at the macro-scale.
The second breakthrough realized, concerns the multiscale model for acoustic metamaterials (AM). These materials have specially fabricated microstructures capable of advanced manipulation of sound waves such as band-pass filtering, redirection, channelling, multiplexing etc. that is otherwise impossible to achieve using ordinary materials. Within MECHMAM a novel and versatile numerical multi-scale technique has been developed for the simulation and analysis of complex elasto-dynamics of acoustic metamaterials. An extended homogenization technique for modelling materials with local resonances is proposed, resulting in an accurate description of the effective macroscopic continuum in a low frequency regime. The resulting equations constitute an enriched (micromorphic) continuum in which additional kinematic degrees of freedom emerge to account for local resonance effects which would otherwise be absent in a classical continuum. This result enables the development of a multiscale semi-analytical analysis technique for locally resonant acoustic metamaterials, allowing for fast transmission and dispersion analyses for arbitrary and complex micro-structure designs. The model has also been generalized in the project in order to account for both Bragg scattering and local resonance effects.
The third break-through is the development of the ‘metafoam’ concept. Metafoams are based on the combination of the working principle of acoustic foams (relying on visco-thermal energy dissipation due to the foam cell structure), combined with the local resonance phenomenon, originating from implanted small masses (smaller than the cell structure). While the former mechanism is effective in the mid- and high-frequency acoustic regimes, the latter can significantly enhance the low-frequency sound protection. Within MECHMAM, the metafoam concept has been introduced, and theoretically and numerically assessed and demonstrated. Upscaling from lab samples to mass production routes should be at reach in the near future.
Other important scientific achievements in the project are:
• identification and extraction of micro-fluctuation fields in heterogeneous strain or displacements fields, which is relevant for damaging microstructures or patterning metamaterials
• a novel global digital imaging correlation technique, which identifies extracts pre-defined fluctuation patterns of experimental images (including imaging artefacts).
• a novel model reduction approach, relying on the use of wavelets for approximating the mechanical fields, allowing for direct error control
• a full-field kinematical experimental analysis of meta-structural cells with embedded resonators