244
According to information on the website of the Coorstek Company, “CoorsTek
produces ceramic armor components used as the ballistic armor strikeface of lightweight composite armor systems. CeraShield™ ceramics, working in conjunction
with an appropriate backing system, can defeat various threats including armorpiercing rounds” (see for details Ceramic Armor/Military Defense & Security: published on-line http://www.coorstek.com/products/ceramic-armor.asp?gclid=CMbp
vtPX7rECFQFAzQodoxIAEQ) .
Since 2009, US Army funded engineers at MIT ( Institute for Soldier
Nanotechnologies , Director Prof. Christine Ortiz), which are studying materials
properties and natural design principles of fi sh scales with the goal to use the knowledge in development of novel lighter and more fl exible armor for military use.
Besides sticklebacks, scientists used “dinosaur eel”, the Polypterus senegalus ,
which can be found in the muddy freshwater shallows in Africa. The body of this
species is covered with multiple scale layers, each of which is about 100 μm thick
(see for details Bruet et al. 2008 ). Characteristic properties of ancient as well as
modern wish species with elasmoid scales like light weight and fl exibility ( Vernerey
and Barthelat 2010 ), transparency and breathability (Zhu et al. 2012a , b ) are of
interest for materials scientists today. Additionally, studies on resistance to penetration using perforation tests with a sharp needle (tip radius = 25 μm) indicated that a
single 200–300 μm thick fi sh scale of striped bass ( Morone saxatilis ) shows a high
resistance to penetration which is superior to artifi cial polymers like polycarbonate
and polystyrene. Here, the results of such kind of experiments reported by Zhu and
co-authors ( 2012a , b ):
“Under puncture, the fi sh scale undergoes a sequence of two distinct failure
events: First, the outer bony layer cracks following a well-defi ned cross-like pattern
which generates four ‘fl aps’ of bony material. The defl ection of the fl aps by the
needle is resisted by the collagen layer, which in biaxial tension acts as a retaining
membrane. Remarkably this second stage of the penetration process is highly stable,
so that an additional 50 % penetration force is required to eventually puncture the
collagen layer. The combination of a hard layer that can fail in a controlled fashion
with a soft and extensible backing layer is, probably, the key to the resistance to
penetration of individual scales,” (Zhu et al. 2012b ). It was shown that “while the
bony layer is brittle, the collagen layer can undergo large deformations, eventually
failing by extensive fi ber pullout,” (Zhu et al. 2011 ).
5.1 Biomechanics of Fish Scales
From the structure-function relationship point of view, the fi sh scale is constructed
during evolution from hierarchically organized biological materials in the multilayered form (Fig. 5.9 .) that determined both excellent protective and hydrodynamics
properties. As biocomposite-based structures, fi sh scales provide a protective layer
resisting penetration by pathogenic microorganisms and providing a physical barrier against attack from predators, as well as abrasive and wear-resistance against
5 Materials Design Principles of Fish Scales and Armor
According to information on the website of the Coorstek Company, “CoorsTek
produces ceramic armor components used as the ballistic armor strikeface of lightweight composite armor systems. CeraShield™ ceramics, working in conjunction
with an appropriate backing system, can defeat various threats including armorpiercing rounds” (see for details Ceramic Armor/Military Defense & Security: published on-line http://www.coorstek.com/products/ceramic-armor.asp?gclid=CMbp
vtPX7rECFQFAzQodoxIAEQ) .
Since 2009, US Army funded engineers at MIT ( Institute for Soldier
Nanotechnologies , Director Prof. Christine Ortiz), which are studying materials
properties and natural design principles of fi sh scales with the goal to use the knowledge in development of novel lighter and more fl exible armor for military use.
Besides sticklebacks, scientists used “dinosaur eel”, the Polypterus senegalus ,
which can be found in the muddy freshwater shallows in Africa. The body of this
species is covered with multiple scale layers, each of which is about 100 μm thick
(see for details Bruet et al. 2008 ). Characteristic properties of ancient as well as
modern wish species with elasmoid scales like light weight and fl exibility ( Vernerey
and Barthelat 2010 ), transparency and breathability (Zhu et al. 2012a , b ) are of
interest for materials scientists today. Additionally, studies on resistance to penetration using perforation tests with a sharp needle (tip radius = 25 μm) indicated that a
single 200–300 μm thick fi sh scale of striped bass ( Morone saxatilis ) shows a high
resistance to penetration which is superior to artifi cial polymers like polycarbonate
and polystyrene. Here, the results of such kind of experiments reported by Zhu and
co-authors ( 2012a , b ):
“Under puncture, the fi sh scale undergoes a sequence of two distinct failure
events: First, the outer bony layer cracks following a well-defi ned cross-like pattern
which generates four ‘fl aps’ of bony material. The defl ection of the fl aps by the
needle is resisted by the collagen layer, which in biaxial tension acts as a retaining
membrane. Remarkably this second stage of the penetration process is highly stable,
so that an additional 50 % penetration force is required to eventually puncture the
collagen layer. The combination of a hard layer that can fail in a controlled fashion
with a soft and extensible backing layer is, probably, the key to the resistance to
penetration of individual scales,” (Zhu et al. 2012b ). It was shown that “while the
bony layer is brittle, the collagen layer can undergo large deformations, eventually
failing by extensive fi ber pullout,” (Zhu et al. 2011 ).
5.1 Biomechanics of Fish Scales
From the structure-function relationship point of view, the fi sh scale is constructed
during evolution from hierarchically organized biological materials in the multilayered form (Fig. 5.9 .) that determined both excellent protective and hydrodynamics
properties. As biocomposite-based structures, fi sh scales provide a protective layer
resisting penetration by pathogenic microorganisms and providing a physical barrier against attack from predators, as well as abrasive and wear-resistance against
5 Materials Design Principles of Fish Scales and Armor