Bone-inspired Materials With Self-adaptable Mechanical Properties & Damage Mitigation and Architected Materials With Adaptive Energy Absorption

events hall

Prof. Sung Hoon Kang

07.04.2022

David Wang Auditorium, 3rd floor Dalia Meidan Bldg.

14:30

Adaptability is one of the hallmarks of living organisms that provide resilience to survive and flourish in dynamically changing environment. I will present our ongoing efforts about how we can realize materials and structures that can adapt to mechanical environment changes by adjusting their mechanical properties autonomously.

First, I will present self-adaptive materials that can change their mechanical properties depending on loading conditions. Nature produces outstanding materials for structural applications such as bones and woods that can adapt to their surrounding environment. For instance, bone regulates mineral quantity proportional to the amount of stress. It becomes stronger in locations subjected to higher mechanical loads. This leads to the formation of mechanically efficient structures for optimal biomechanical and energy-efficient performance. However, it has been a challenge for synthetic materials to change and adapt their structures and properties to address the changes in loading conditions. To address the challenge, we are inspired by the findings that bones are formed by the mineralization of ions from blood onto scaffolds. I will present a material system that triggers mineral deposition from ionic solutions on scaffolds upon mechanical loadings so that it can self-adapt to mechanical loadings. For example, the mineralization rate could be modulated by controlling the loading condition and a 30-180% increase in the modulus of the material was observed upon cyclic loadings whose range and rate of the property change could be modulated by varying the loading condition. Moreover, our preliminary results showed that the material system showed a decrease in crack propagation speed by ~90%, resulting in significantly improved fatigue lifetime from its damage mitigation mechanism. We envision that our findings open new strategies for making synthetic materials with self-adaptable mechanical properties.

Second, an architected material (or metamaterial) is a class of materials that provide new properties that are not observed in natural materials or from a bulk material that the “material” is made of. I will present adaptive energy-absorbing “materials” with extreme energy dissipation and improving energy absorption with increasing strain rate by the synergy of nonlinear behaviors of materials and structures. We utilize energy dissipation mechanisms across different length scales by utilizing architected liquid crystalline elastomers. As a result, our energy-absorbing materials show about an order of magnitude higher energy absorption density at quasi-static condition compared with the previous studies and even higher energy dissipation at faster strain rates with power-law relation, whose exponent can be tuned by controlling the mesoscale alignment of molecules using a simple strain control-based approach. We also found that we can further enhance the energy absorption density by vertical stacking due to viscoelasticity. The findings from our study can contribute to realizing extremely lightweight and high energy dissipating materials, which will be beneficial for various applications, including aerospace, automotive, and personal protection

Host: Prof. Boaz Pokroy