Date of Award
5-2024
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Committee Chair/Advisor
Dr. Zhaoxu Meng
Committee Member
Dr. Zhen Li
Committee Member
Dr. Xin Zhao
Abstract
Natural protective materials offer unparalleled solutions for impact-resistant material designs that are simultaneously lightweight, strong, and tough. Particularly, the dactyl club of mantis shrimp features chitin nanofibrils organized in a Bouligand structure, which has been shown to effectively dissipate high-impact energy during powerful strikes. The mollusk shells also achieve excellent mechanical strength, toughness, and impact resistance with a staggered, layer-by-layer structure. Previous studies have shown that hybrid designs, by combining different bioinspired microstructures, can lead to enhanced mechanical strength and energy dissipation capabilities. Nevertheless, it remains unknown whether combining Bouligand and staggered structures in nanofibrillar cellulose (NFC) films, forming a discontinuous fibrous Bouligand (DFB) architecture, can achieve enhanced impact resistance under localized ballistic impact. Additionally, the failure mechanisms under such dynamic loading conditions have been minimally understood. In this thesis, I present a comprehensive study to investigate the dynamic failure mechanisms and quantify the impact resistance of NFC thin films with DFB architecture by leveraging previously developed coarse-grained models and explicit projectile impact molecular dynamics simulations. The results show that when nanofibrils achieve a critical length with the DFB architecture, the impact resistance of NFC films outperforms the counterpart films with continuous fibrils by comparing their specific ballistic limit velocities and penetration energies. I also look into the underlying mechanisms contributing to this improvement in impact resistance, which include iii enhanced fibril sliding initiated at the discontinuous sites, intralayer and interlayer crack bridging, and crack twisting mechanism in the thickness direction enabled by the DFB architecture. Overall, the results in this thesis show that by combining Bouligand and staggered structures in NFC films, their potential for protective applications can be further improved. The findings presented in this thesis can provide practical guidelines for the design of protective films made of nanofibrils.
Recommended Citation
Caviness, Colby, "Improved Ballistic Impact Resistance of Nanofibrillar Cellulose Films With Discontinuous Fibrous Bouligand Architecture" (2024). All Theses. 4295.
https://open.clemson.edu/all_theses/4295
Included in
Applied Mechanics Commons, Biology and Biomimetic Materials Commons, Manufacturing Commons, Mechanics of Materials Commons