Next-generation structural materials are anticipated to be tough, lightweight and high-strength with embedded functionalities like uniform stress distribution, tunable response, avoid catastrophic failure and reusable. Natural materials have mastered these properties by evolving in a multifunctional hierarchical form with dimensional characteristics ranging from nano to macro scales. The hierarchical architecture comes in different shapes, like cellular morphology, amorphous foams, microplatelets lamellas, lamellar pillars, etc. Current research work is focused on the cellular morphology observed in the Euplectella aspergillum (E. aspergillum) and Columba livia (C. livia).
E. aspergillum is a glass sponge mainly found in the deep under water of the Pacific Ocean. Their cylindrical skeleton consists of a regular square lattice with a series of vertical, horizontal and diagonal silica struts. Together these struts result in a near optimal strut-based design. In the current research work, the static and dynamic mechanical behavior of the E. aspergillum inspired cellular structures is studied both using experiments and computational methods. For fabrication additive manufacturing (AM) techniques with polymers and alloy are used. In the static mechanical behavior, recoverable energy absorption is considered. The work also developed a method to enhance the energy absorption by using nacre like dual polymers in a same cellular structure. The overall energy absorption is better than most of the cellular structures reported across the literature, with dual polymer-based structure showed energy absorption close to the metallic cellular structures, while maintaining the reversibility which has not been observed in the metallic cellular structures. The elastic constants of the E. aspergillum inspired cellular structures are formulated using energy-based method and parametric study is carried out to study the effect of unit cell parameters on the elastic modulus and Poisson’s ratio. The results showed tunable mechanical response with wide range of properties varies between bending and stretch dominating behavior. Dynamic studies are carried on the bionic cylindrical thin tubes inspired from the skeleton of the E. aspergillum. In case of dynamic mechanical behavior, high-speed impact absorption, cyclic fatigue and high-temperature creep are considered.
High speed impact absorption behavior is better than the other type of bionic tubes reported in the literature and traditional solid crash boxes. In the fatigue loading, comparison has been made between E. aspergillum and honeycomb based thin tubes for the effect of the constant and variable amplitude loading on the fatigue life and fracture mechanism. The variable amplitude fatigue loading showed more detrimental effect on the fatigue life and honeycomb based thin tubes showed the worst fatigue life. Similar comparison has been made for high-temperature creep life. Here also E. aspergillum inspired tubes showed higher creep life.
C. livia are the bird feather, the hierarchical architecture is evolved to carry aerodynamic load during the bird flight. In the current research work, different elements of the C. livia together modelled in the form of cellular structures. These cellular structures are studied for different static behavior like compressive strength, flexural performance and crack propagation. The compressive strength and flexural behavior are compared with the honeycombs and results showed significant improvement over the mechanical response. Also, the crack path in the C. livia inspired structures is dependent on the unit cell parameters. Such type of the cellular structures when incorporated in the full-scale designs can create fail-proof components.