DOCTORAL CANDIDATE
Manish Kumar

SUPERVISORS
Prof. Philippe Viot
Prof. Paul Hazell

Mechanics, Materials

Life on earth has evolved to aid the growth and survival of various species for billions of years. Humans have been trying to learn from and imitate natural materials for millennia. Over the millennia, lightweight natural structures have developed heterogeneous architectures to cope with quasi-static, cyclic or impact mechanical loading conditions. One of the features observed in many biological structures is the density gradient. Such features have been shown to improve the mechanical properties of architectural structures.
Lightweight structures with high energy absorption capacity are becoming increasingly popular in a variety of technical sectors, including aviation, transportation, the nuclear industry, and civil engineering.
The development of new additive manufacturing processes has changed the way we consider process/microstructure/properties relationships of materials. Furthermore, the architectured structures obtained by additive manufacturing can be specifically designed to be used as energy absorbers in the case of an impact, shock, or ballistic loading. The lightweight of these structures and their capability to dissipate energy are advantageous for the development of components for crashworthiness or other protective applications.
There is a current lack of detailed understanding of the underlying strain mechanisms of biological and bio-inspired structures during mechanical loading and their dependence on strain and strain rate.

The research will start with characterizing the density gradient in biological structures using SEM and microtomography and then conceive and produce the architectured samples by using 3-D metallic additive manufacturing with a bioinspired density gradient. Then, identify experimentally the mechanical behaviour of the architectured material at different strain rates with a high-speed jack, Hopkinson bars and high-velocity gas gun. The final step of this study is to correlate and model the effect of the density gradient on the response of the 3D printed material to mechanical loading.