Architected cylinders: design, micro-mechanics, additive manufacturing, and sensing capabilities characterization

Abstract

Architected matter could bring advantages that their fully solid counterparts cannot. Understanding their mechanics unveils critical elements impacting the overall structure deformation and monitoring these elements offers insights into structural behavior. This thesis encompasses the mechanical analysis of architected cylinders and how they could be used as sensing structures. Additionally, their potential in acquiring data from human grip strength is explored as a proof-of-concept. Hexagonal, re-entrant, and square rotated architected cylinders were parameterized in both rectangular and cylindrical cell arrangements. In the latter, the number of rotational degrees of symmetry was varied to evaluate their impact on the structures’ mechanical properties. After applying uniform pressure via computational simulations to the surfaces of the structures, it was found that the orientation of cell walls with respect to the applied load influenced their radial stiffness and deformation mechanism. Re-entrant models were the most flexible, while the square rotated ones were the stiffest. The deformation mechanism varied in re-entrant models when changing the rotational degrees of symmetry, which was attributed to the variation in length between concentric and non-concentric. The analysis of compression tests on 3D architected cylinders revealed that cylinders with a higher number of rotational degrees of symmetry, a rectangular cell arrangement, and a hexagonal topology exhibited stiffer behavior. Re-entrant models demonstrated auxetic behavior when one or more unit cells were aligned with the direction of the applied load. Concentric cell walls deformation was quantified using a curvature-based approach, comparing the area under the curvature function of a cell wall with the area of the undeformed cell wall. This ratio was compared to voltage signal of piezoresistive sensors that were inserted in the cell walls of architected cylinders. A relation was found between voltage and area under curvature ratios, suggesting sensor data reflects cell wall’s deformation. Two subjects tested the cylinders’ hand-gripping performance, yielding similar deformed shapes to those in the diametrical compression. This suggests that the curvature-based approach and sensors’ integration are methods that can contribute to the development of an architected de vice capable of obtaining hand-gripping information. Further work to achieve this objective may involve conducting mechanical characterization studies with varied orientations of cell arrangements relative to the applied load. Additionally, adjusting the dimensions of sensing cylindrical structures based on anthropometric percentile data could enhance conformity to the hand morphology of specific populations.