Multiscale tunability of solitary wave dynamics in tensegrity metamaterials

Abstract

A new class of strongly nonlinear metamaterials based on tensegrity concepts is proposed and the solitary wave dynamics under impact loading is investigated. Such systems can be tuned into elastic hardening or elastic softening regimes by adjusting local and global prestress. In the softening regime these metamaterials are able to transform initially compression pulse into a solitary rarefaction wave followed by oscillatory tail with progressively decreasing amplitude. Interaction of a compression solitary pulse with an interface between elastically hardening and softening materials having correspondingly low-high acoustic impedances demonstrates anomalous behavior: a train of reflected compression solitary waves in the low impedance material; and a transmitted solitary rarefaction wave with oscillatory tail in high impedance material. The interaction of a rarefaction solitary wave with an interface between elastically softening and elastically hardening materials with high-low impedances also demonstrates anomalous behavior: a reflected solitary rarefaction wave with oscillatory tail in the high impedance branch; and a delayed train of transmitted compression solitary pulses in the low impedance branch. These anomalous impact transformation properties may allow for the design of ultimate impact mitigation devices without relying on energy dissipation.

Accurate Numerical Methods for Studying the Nonlinear Wave-Dynamics of Tensegrity Metamaterials

“…3). While compression solitary waves in uniform granular chains have a constant width, which is independent of the amplitude [29], the width of similar waves in tensegrity metamaterials changes with amplitude and speed, and the solitary wave tends to concentrate on a single lattice spacing in the high energy regime [15,4].…”

“…Recent studies have shown that tensegrity lattices exhibit a tunable geometrically nonlinear response, which switches from stiffening to softening by playing with a number of mechanical, geometrical, and prestress variables [1,2,3,4]. Tensegrity lattices consists of networks of prestressable truss structures, obtained by connecting compressive members (bars or struts) through pre-stretched tensile elements (cables or strings).…”

“…Equally, there is growing interest in research into noninvasive tools to target defects in materials, and for monitoring structural health in materials and structures [16,17,18,19]. Highly efficient and unconventional mechanisms for protecting materials and focusing mechanical waves through the use of rarefaction and compression solitary waves have recently been discovered by [4,15]. It is worth noting that arrays of tensegrity lattices with elastically hardening response can be employed to fabricate tunable focus acoustic lenses that support extremely compact solitary waves [4,15].…”

On the Use of Mechanical Metamaterials for Innovative Seismic Isolations Systems

“…Second, physical models of pentamode isolators need to be constructed, employing, e.g., additive manufacturing techniques [8,9], and laboratory tested as seismic base-isolation devices [19], in order to experimentally asses their isolation and dissipation capabilities arising, e.g., from inelastic response and/or material fracture [20]. Another relevant generalization of the present research regards the design of dynamically tunable systems based on the insertion of prestressed cables and/or curved rods within pentamode lattices, with the aim of designing novel metamaterials and bio-inspired lattices tunable by local and global prestress [12][13][14][21][22][23][24][25][26][27][28]. Future studies will also address the experimentation of pentamode materials as components of new-generation seismic dampers.…”

“…These may include: exceptional strength-and stiffness-to-weight ratios; excellent strain recoverability; very soft and/or very stiff deformation modes; auxetic behavior; phononic bandgaps; sound control ability; negative effective mass density; negative effective stiffness; negative effective refraction index; superlens behavior; and/or localized confined waves, to name some examples (cf. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and references therein). The category of "extremal materials" has been introduced in [3] to define materials that simultaneously show very soft and very stiff deformation modes (unimode, bimode, trimode, quadramode and pentamode materials, depending on the number of soft modes).…”