Mechanical properties of 3D re-entrant honeycomb auxetic structures realized via additive manufacturing

HCI meets Material Science

“…However, their widespread use has largely been limited by the complex procedures to generate these materials using traditional manufacturing methods. With recent advances in 3D printing, the potential exists to more readily fabricate cellular designs to introduce shape-changing functionality, particularly in the case of 3D re-entrant structures [118,149,153,260]. For example, Theodoros et al [235] 3D printed an auxetic structure that could be pneumatically actuated to achieve a change in curvature, and in [99] the authors 3D printed a metamaterial door latch from a single block of NinjaFlex (a flexible TPU filament) that enabled rotary movement of the handle to be transformed into linear motion of the latch.…”

Challenges of additive manufacturing technologies from an optimisation perspective

“…Here are some of these considerations that are central to the development of robust AM solutions: -Geometry of the CAD model: this is direct target of the topology optimisation, which needs to predict what would be the exact geometry that satisfies all model constrains. Successful examples of topology optimisation can be found in the literature for cellular materials [88,89], multiphase materials [37], implants [90]. -Path generation: this is an important parameter that affects geometry accuracy, cohesion in the part, residual stresses, and the finishing state [20,63,91].…”

Mechanical properties in tensile loading of H13 re-entrant honeycomb auxetic structure manufactured by direct metal deposition

“…For characterising mechanical properties such as Youngs' modulus and Poisson's ratio, the number of unit cell repetition can be critical. However, for reentrant honeycomb auxetic structure, for estimating effective Young's modulus and Poisson's ratio, the number of unit cell repetitions greater than four has no size-effect [11]. …”