Parametric Design and Mechanical Characterization of 3D-Printed PLA Composite Biomimetic Voronoi Lattices Inspired by the Stereom of Sea Urchins

Abstract

The present work is focused on the analysis of the microstructure of the exoskeleton of the sea urchin Paracentrotus lividus and the extraction of design concepts by implementing geometrically described 3D Voronoi diagrams. Scanning electron microscopy (SEM) analysis of dried sea urchin shells revealed a foam-like microstructure, also known as the stereom. Subsequently, parametric, digital models were created with the aid of the computer-aided design (CAD) software Rhinoceros 3D (v. Rhino 7, 7.1.20343.09491) combined with the visual programming environment Grasshopper. Variables such as node count, rod thickness and mesh smoothness of the biologically-inspired Voronoi lattice were adapted for 3D printing cubic specimens using the fused filament fabrication (FFF) method. The filaments used in the process were a commercial polylactic acid (PLA), a compound of polylactic acid/polyhydroxyalkanoate (PLA/PHA) and a wood fiber polylactic acid/polyhydroxyalkanoate (PLA/PHA) composite. Nanoindentation tests coupled with finite element analysis (FEA) produced the stress–strain response of the materials under study and were used to simulate the Voronoi geometries under a compression loading regime in order to study their deformation and stress distribution in relation to experimental compression testing. The PLA blend with polyhydroxyalkanoate seems to have a minor effect on the mechanical behavior of such structures, whereas when wood fibers are added to the compound, a major decrease in strength occurs. The computational model results significantly coincide with the experimental results.

3D Printed Voronoi Structures Inspired by Paracentrotus lividus Shells

“…The verified material model from the FEA-supported nanoindentation method [5] has been introduced into the FE model to assess the compression performance of the Voronoi structures. Furthermore, a computational model was utilized to assess the stress response of the 3D printed specimens when subjected to compression.…”

“…A parametric design algorithm, emulating the morphogenetic process of a 3D Voronoi diagram [5], was developed with the aid of the computer-aided design (CAD) software Rhinoceros 3D and Grasshopper 3D (v. Rhino 7, 7.1.20343.09491, Robert McNeel & Associates, Seattle, WA, USA) in a previous stage of this research. A custom set of points is created within a bounding geometry.…”

“…A baseline model (Model 1) was established [5], with XYZ dimensions of 40 mm× 40 mm × 40 mm, node count of 60, rod radius 1.8 mm, and smoothness scale 1. Variations of this model were generated with successive changes in geometric parameters that define a 3D Voronoi structure and have significant impact on its relative density [14].…”

“…Such structures are a product of billions of years of natural evolution and manage to achieve exceptional mechanical properties while maintaining low weight and minimal usage of material and energy [4], traits that are vital for the survival of organisms in nature. More specifically, the shell of the sea urchin Paracentrotus lividus has been shown, under scanning electron microscope (SEM) analysis, to be comprised of a porous structure known as the stereom which resembles a foam, as illustrated in Figure 1 [5]. The porous calcite shell provides the urchin with the necessary toughness and impact resistance to protect itself from environmental threats and predators [6][7][8].…”

Digital Biomimicry: Developing an algorithmic design curriculum

“…The research will further expand on the variance of the typological design permutations, the efficiency of modeling and performance quantification workflows through the use of surrogate machine learning models and the alignment with building codes and complex design criteria for high performing buildings with regards to energy efficiency, user experience, space efficiency and structural design. Similarly, the research focusing on biomimetic design and fabrication examines topics of biological organisms and their process of morphogenesis to extract principles that will be used for prototyping with the aid of additive manufacturing (AM) technologies (Efstathiadis et al, 2022). A systematic strategy of biomimetic design was established within the context of doctorate research synthesizing digital technologies of analysis, emulation, and technical implementation.…”