Biomimicry and additive manufacturing: from materials to functional structures
Creators: name: Tee, Yun Lu
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400510
subject: Structural engineering

description: There has been a drastic change in the manufacturing industry over the years. In the past, conventional manufacturing, such as injection moulding, casting, and milling are used to produce simple monolithic parts at large quantities and low production costs. However, with the demand in part complexity, multi-material and multi-colour, it is challenging to achieve all requirements via conventional manufacturing. With the advancement of manufacturing technology, Additive Manufacturing or 3D printing allows the production of parts with a high degree of complexity layer-by-layer, requiring minimal post-processing. This has attracted various industries, including aerospace, automotive and construction, to convert part of traditional manufacturing to additive manufacturing. 

In the effort to produce parts with exceptional mechanical performances, researchers find their source of inspiration from nature. Nacre, bamboo, bone, lobster shell and sea urchin spine are among several popular subjects for bioinspiration, known for their lightweight, graded or composite arrangements. Hierarchical and graded structures are among the most popular designs employed in flora and fauna. Various patterns are found in nature, including fractals, stripes, spirals, and tessellations.

Natural composites are made of simple organic materials but possess extraordinary toughness or stiffness. The uniqueness raises the interest of researchers in exploring growth patterns. The irregular puzzle-like patterns on the giraffe’s fur and dragonfly wing are known as Voronoi tessellation. This tessellation is created based on partitioning a plane with a number of seeds into polygons, where a point is closer to the generating seed within the polygon than any other. Despite the fact that the study of Voronoi tessellation has existed for more than a century, there is still a great interest in the mechanical properties of Voronoi-based structures.  

This study aimed to bridge nature design and additive manufacturing to understand the mechanical behaviour of bioinspired structures. The material jetting technology is employed in this study due to its high resolutions and multi-material printing capability for mimicking biomaterials. The dimensional fidelity, mechanical performance and fractography of the 3D printed composites are explored.

Upon a thorough understanding of the 3D printing technology, the morphology of the biomaterial – porcupine quill is investigated. Micro-computed tomography is employed to explore the internal morphology of the sample through x-ray projection images. The mechanical performance of porcupine quill is explored. Compression of the whole, shell-only and foam-only porcupine quill is investigated. It is found that among the three sample types, the whole quill performed the best compared to the shell-only and foam-only counterparts. The presence of foam has greatly affected the failure mechanism of the porcupine quill, which motivated the design of the bioinspired structure carried out in the next section.

Following the revelation of the porcupine quill’s structures, porcupine quill-inspired designs are proposed in via 2D and 3D approaches. From a 3D perspective, random and reflected foam structures are designed according to the features observed on the cross-section of a porcupine quill. On the other hand, from a 2D perspective, Voronoi sandwich panels are designed to understand the flexural properties by incorporating graded seed distribution. In addition, finite element analysis is conducted for validation. A parametric study is conducted to understand further the effect of geometry variation on the Voronoi sandwich panels. The potential applications of the bioinspired structures include aerospace and automobile industry as a shock absorber and light weight structures.