Bioinspired, Helical and Sinusoidal Architected Concrete Enabled by Robotic Additive Manufacturing

Abstract

Nature has developed abundant biological design motifs for arranging modest materials into complex, damage-tolerant architectures. The bouligand architecture found in the endocuticle of the mantis shrimp dactyl club is comprised of rows of fibrils forming sheets which stack helically atop each other. The double-bouligand architecture found in the scales of the coelacanth fish are similarly comprised of helically arranged sheets of collagen fibrils, however, each sheet is coupled with a second perpendicular layer of fibrils to form an orthogonal bilayer unit. The sinusoidal architecture is found at multiple length scales in several bivalve mollusks, for instance in the sinusoidal corrugations of the shell geometry, or the microstructure of the shell comprised of an undulating arrangement of aragonite platelets. Here, one-component and two-component robotic additive manufacturing processes were established to engineer architected concrete with bio-inspired toughening mechanisms including crack twisting, deflection, and shielding, occurring ahead and behind the crack tip. Experimental flexural and fracture tests (Mode-I) were conducted to characterize modulus of rupture, fracture toughness, and work of fracture. The architected concrete successfully increased fracture toughness and work of fracture compared to cast conventionally 3D-printed counterparts, without compromising flexural strength. The experimental findings were further studied through micro-computed tomography to examine the weak interface, and finite element simulations to interpret stress distributions. Harnessing the bio-inspired motifs can engender a pathway for leveraging reliable crack-resistance in the design of resilient additively manufactured concrete structures. Moreover, by leveraging bioinspired architectures, additively manufactured concrete infrastructure can be designed to have greater mechanical performance than what is achievable with conventional construction methods.