Auxetic honeycombs with lossy polymeric infills for high damping structural materials

Structural grade materials with Young's Modulus in the gigapascal range generally have very low damping, leading to requirement for auxiliary damping treatments in many applications. This article examines whether a high Young's Modulus and damping level can simultaneously be realized by introducing lossy polymeric infills into auxetic aluminum honeycombs. Using finite element analysis, auxetic honeycombs with varying cell geometry and infill stiffness, loaded in the x-and y-directions, are examined. From the results, it is observed that the best performance is achieved when auxetic honeycombs with shallow inclined walls and short vertical walls are loaded in the x-direction. Young's Modulus in excess of 10 GPa is achievable in combination with a loss factor of 5%. If a higher loss factor of 10% is required, Young's Modulus in the range of 5.5-6.5 GPa can still be realized. The high loss factors achieved are attributed to the very high local strain levels in the polymeric infill in the central region of the cell between the top and the bottom cell walls, which are in close proximity, further increased by the large negative Poisson's ratios of the configuration.