Energy absorbing multilayered self-recovering metamaterials with chiral topology

A novel energy absorbing material is proposed for the design of shock absorbers and vibrational dampers. A layered architectured microstructure is put forward consisting of the repetition of plane lattices having hex­ achiral topology with alternate chirality, each being designed as a periodic assembly of rigid disks connected by elastic ligaments. Because of the chiral topology of the single layer, the rotation of the rigid disks takes place when in-plane stress states are applied so implying a relative rotation between the disks of adjacent lattices with opposite chirality. Pins passing through for each stacking of disks impose them the same in-plane displacement. Moreover, frictional dissipative mechanisms at the interface between adjacent disks according to two different compression modes orthogonal to the layers make the metamaterial suitable for either reusing or self-recovering the initial configuration. In the first case the pre-tensioning of the pins implies the compression of plane frictional interfaces. The frictional sliding compatible with the disk relative rotation implies an overall hysteretic bilinear response with remarkable energy dissipation. The metamaterial may be reused once the pins are relaxed and re- tensioned. In the latter case no pre-tension is applied to the pins and the compressive force between the disks is obtained through saw-tooth shaped interfaces between adjacent disks to get elastically constrained transverse dilation when the relative rotations at the interfaces take place. The overall response turns out to be highly dissipative and self-recovering, i.e. able to return to the initial configuration when removing the applied stresses. As shown in the examples the quasi-static behavior of the proposed metamaterial makes it a candidate as an efficient vibration damper and a shock absorber characterized by i) hysteretic response with remarkable energy dissipation under biaxial stress states; ii) reuse or self-recovering after the energy absorption event; iii) bilateral response, i.e. equal behavior under both tension and compression.