Comparative investigation of full bandgap behaviors of perforated auxetic metaconcretes with or without soft filler

The metaconcretes engineered by embedding steel balls coated by soft rubber in concrete matrix offer great potential in controlling wave propagation. However, the relatively high start frequencies of bandgaps and deadweights may limit their applications. In this work, an alternative lightweight metaconcrete design is realized by perforated auxetic materials structured by aligning orthogonally peanut-shaped holes in concrete matrix. Meanwhile, the filling case by rubber is considered as well for a comparative purpose. Then a systematic investigation is conducted for the unfilled and filled auxetic metaconcretes to reveal their full bandgap characteristics and vibration mechanism. The results indicate that the perforated auxetic metaconcretes exhibit wide potential in wave control. The combination of soft and hard materials leads to the occurrence of local resonance, instead of the classic Bragg scattering in the unfilled structure. Moreover, the unfilled structure can produce a large complete bandgap in kHz with large bandgap width, while the composite structure exhibits good wave attenuation capability in extra lower frequency below 50 Hz, although its bandgap width looks a bit narrow and needs to be optimized further. Then, the relationship between the wave isolation performance and the key structural parameters, i.e. structural porosity and stiffness-to-density ratio of material, is identified. Finally, it is worth noting that the overall mechanical properties of the present metaconcretes are insensitive to the soft filling material. This provides a promising ability in separately altering the load-bearing and bandgap properties.