Sung Hoon Kang

"Adaptive and Self-Repairing Materials"

ABSTRACT -- 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 their mechanical loading environments 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 structural materials that can adapt to their environments. For example, bone becomes stronger in locations subjected to higher mechanical loads. I will present a material system which could model that behavior, by triggering mineral deposition from ionic solutions on scaffolds when the material is under stress. Thus the material could self-reinforce when mechanically loaded. Our system showed a 30-180% increase in the modulus of the material under cyclic loading. Preliminary results showed a decrease in crack propagation speed, resuling in improved fatigue life.

Second, I will discuss architected materials, also known as metamaterials. Metamaterials 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 metamaterials with extreme energy dissipation. The energy absorption improves with increasing strain as a result of 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. 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.

SPEAKER -- Sung Hoon Kang is an Assistant Professor in the Department of Mechanical Engineering at Johns Hopkins University. He earned a Ph.D. degree in Applied Physics at Harvard University and M.S. and B.S. degrees in Materials Science and Engineering from MIT and Seoul National University, respectively. Sung Hoon has been investigating solutions to address current challenges in engineering materials, structures and devices with applications including resiliency, sensing, energy, and healthcare. In particular, he investigates synthesis and manufacturing of materials and structures with novel properties based on principles of mechanics and physics and tools such as numerical modeling, 3D printing, 3D structural/material/mechanical characterizations, and in vitro/in vivo testing. His research has been supported by NSF, NIH, and the State of Maryland, among others.

Sung Hoon has co-authored 55 papers, has given > 150 presentations. He has six patents and five pending patents. His honors include Hanwha Non-Tenured Faculty Award, Air Force Summer Faculty Fellowship, Johns Hopkins University Catalyst Award, and many others. He served as an editorial board member of Scientific Reports and a guest editor of Materials Research Society Bulletin. Currently, he serves as an editorial board member of Multifunctional Materials and Sensors, respectively. He has co-organized symposia on bioinspired materials, 3D printing, and mechanical metamaterials. He is a member of American Society of Mechanical Engineers (ASME), Materials Research Society (MRS), American Physical Society (APS), and Society of Engineering Science (SES). He served on the ASME Technical Committee on Mechanics of Soft Materials.

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