Experimental approximation of the sound absorption coefficient (∝) for 3D printed reentrant auxetic structures of poly lactic acid reinforced with chicken keratin materials

In this research, auxetic composites of polylactic acid (PLA) reinforced by keratin materials (barbs and rachis), were developed through 3D printing manufacture to induce diverse acoustic properties. To evaluate the coefficient of sound absorption, an electro-acoustic experiment was implemented. The capacity of sound absorption for the composites was superior to conventional (honeycomb) and auxetic PLA geometries without reinforcement. Reduction of the free space in cavities (achieved by keratin materials) triggered an increment in the resistance in air flow, improving the sound absorption. Also, increasing the interconnectivity of the cavities provides sound waves with irregular transmission routes, which reduce the wave's energy. Thus, in this work, acoustic properties are associated with 3D geometry of auxetic composites, shape, and concentration of reinforcements; considering the synergistic effect due to this combination, a range of metamaterials with acoustic capabilities were generated. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Auxetic composites of polylactic acid reinforced by keratin materials were developed through 3D printing to induce diverse acoustic properties. The capacity of sound absorption was superior to conventional geometries, achieved by reduction of free space in cavities and increasing interconnectivity to provide irregular sound wave transmission routes. The synergistic effect of 3D geometry, shape, and concentration of reinforcements generated a range of metamaterials with acoustic capabilities.