Vibration isolation performance at low-frequency ranges before resonance is a vital characteristic that conventional springs cannot exhibit. This paper introduces a novel zero Poisson’s ratio graded cylindrical metamaterial to fulfill two main goals: (1) vibration isolation performance in low-frequency bands prior to resonance and (2) global buckling control of a long cylindrical tube. For this purpose, “soft and stiff” re-entrant unit cells with varying stiffness were developed. The cylindrical metamaterials were then fabricated using a multi-jet fusion HP three-dimensional (3D) printer. The finite element analyses (FEA) and experimental results demonstrate that the simultaneous existence of multi-stiffness unit cells leads to quasi-zero stiffness (QZS) regions in the force-displacement relationship of a cylindrical metamaterial under compression. They possess significant vibration isolation performance at frequency ranges between 10 and 30 Hz. The proposed multi-stiffness re-entrant unit cells also offer global buckling control of long cylindrical tubes (with a length to diameter ratio of 3.7). The simultaneous existence of multi-stiffness re-entrant unit cells provides a feature for designers to adjust and control the deformation patterns and unit cells’ densification throughout cylindrical tubes.

Incorporating additive manufacturing (AM) constraints in topology optimisation can lead to performance optimality while ensuring manufacturability of designs. Numerical techniques have been previously proposed to obtain support-free designs in AM, however, few works have verified the manufacturability of their solutions. Physical verification of manufacturability becomes more critical recalling that the conventional density-based topology optimisation methods will inevitably require post-processing to smooth the boundaries before sending the results to a 3D printer. This paper presents the smooth design of self-supporting topologies using the combination of a new Solid Isotropic Microstructure with Penalisation method (SIMP) developed based on elemental volume fractions and an existing AM filter. Manufacturability of selected simulation results are verified with Fused Deposition Modeling (FDM) technology. It is illustrated that the proposed method is able to generate convergent self-supporting topologies which are printable using FDM.