Download or read book Design of Biomimetic Armor Based on Strain Rate Sensitive Natural Dermal Armor written by Sean S. Ghods and published by . This book was released on 2018 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elasmoid fish scales serve as a dermal armor and are a marvelous example of a biological composite in Nature that exhibits exceptional mechanical behavior. Their hierarchical microstructure consists of two distinct and primary regions across the thickness. The outermost layer is known as the limiting layer (LL) and consists of calcium deficient apatite and discrete, sparsely distributed collagen fibers. The second layer is the elasmodine and consists of lamella of uniaxially aligned collagen fibrils with significantly lower mineral content. As collagen is the major constituent of fish scales, they would be expected to exhibit a high degree of strain rate sensitivity. Therefore, an experimental evaluation of the strain rate sensitivity of elasmodine fish scales was conducted in uniaxial tension and transverse puncture loading arrangements. It is shown that across a broad range of strain rates in tension, from 104̄ to 102 s1̄, and ramp rates in transverse puncture, from 0.05 to 50 mm/s, the scales have an exponent for the toughness of 0.10 and 0.35, respectively. The mechanics of collagen depend heavily on intermolecular bonding. Based on their high collagen content, hydrogen bonding can extend across fibrils and interfaces of the lamellae. Thus, a polar solvent (ethanol) was introduced to scales to change the interface bonding and evaluate its effects on the scale’s mechanical behavior. In addition to the strain rate sensitivity, exposure of the scales to ethanol invoked significant increases in the elastic modulus, strength, and toughness across all loading rates. The largest increase noted was a 7X increase in the work to failure for transverse puncture loading. In an effort to apply these findings towards the development of new armors, novel “first-generation” composites were developed with features of the fish scale microstructure. Specifically, fibrous ultra-high molecular weight polyethylene composites were fabricated using Dyneema as a platform and reinforced selectively with alumina particles. The experimental materials were evaluated in the same transverse puncture loading format. The addition of alumina powder to the polymer fiber composite resulted in increases across the performance metrics measured, but not yet to the level achieved by the scales. These results show promise and merit further investigation in the development of composites that draw inspiration from natural dermal armor.