A composite gradient index lens for wideband elastic waves focusing: Design approach and experimental validation at constant thickness
Résumé
Vibrational energy focusing is of significant interest in fields such as energy harvesting, particularly with the emergence of smart structures and self-powered technologies. This paper presents the design and manufacturing approach for Gradient-Index (GRIN) lenses using composite materials. As a proof of concept, the strategy implemented here focuses on controlling the fiber mass ratio of a unidirectional (UD) composite at constant thickness. Mechanical properties must be carefully controlled throughout a dedicated manufacturing process to achieve a gradient of phase velocity for focusing elastic flexural waves. Numerical calculation have demonstrated the efficiency of energy focusing within a frequency range from 2 kHz to 8 kHz. A manufacturing process has been developed to prototype a composite structure that integrates the designed GRIN lens. Additionally, the comparison of a numerical model with experimental results from a manufactured lens structure reveals that the energy density in a defined focusing zone can be increased sevenfold using a gradient lens composite structure, with an incident wave of 8 kHz.
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Est complété par 10.5281/zenodo.16895987 Article Rapine, V., Abuhemeida, N., Ouisse, M., Cogan, S., Francescato, P., Lachat, R., & Meyer, Y. (2025). A composite gradient index lens for wideband elastic waves focusing: Design approach and experimental validation at constant thickness. Zenodo. https://doi.org/10.5281/ZENODO.16895987
Supplementary data : Videos of the propagation of the elastic A0 mode, both numerically and experimentally, in a unidirectional carbon–epoxy composite plate incorporating a passive discrete GRIN lens. The lens is implemented through a fiber mass ratio gradient, and the wave fields are shown for excitation frequencies of 2 kHz and 8 kHz.