Chapter 2 - Mechanical metamaterials

Abstract

The level set-based topology optimization method was adopted to design novel lattice structures. Ti-6Al-4V topology-optimized lattice structures with 30% volume of solid materials were successfully fabricated by selective laser melting (SLM). A study on the mechanical properties and energy absorption capability of the topology-optimized structures was also conducted through quasistatic compressive testing. The findings illustrated that the proposed topology optimization method combined with SLM processing is an effective way to obtain novel lattice structures with high load-bearing and energy absorption capacities. Printed active composites (PACs) are capable of deforming from an initial shape to a target shape via spatial arrangements of active materials within a passive matrix. Multimaterial polymer printers allow precise placement of multiple materials in the design space. However, it is difficult for a single active material to satisfy the demands of high-precision matching of more complex target shapes. Hence, a multimaterial topology optimization approach for the design of PACs is proposed to achieve a target shape under a given stimulus. Mechanical metamaterials, consisting of periodic arrangements of struts, exhibit excellent specific mechanical properties and are of importance for aerospace applications, lightweight construction, bone implants, and energy absorption. However, current mechanical metamaterials are still falling far behind many biological architectures. On the other hand, biological materials often lack design flexibility and controllable structures, and mechanical performances. Here, inspired by the strong and ductile bamboo with a hollow architecture, we constructed three face-centered cubic (FCC) lattice-based mechanical metamaterials via SLM of Ti-6Al-4V with high fidelity. Guided by numerical simulation, these biomimetic structures can be easily tailored through tuning the outer and inner (hollow) diameters, with widely adjustable performances.