250
suppression of catastrophic radial surface cracking, and favoring localized circumferential cracking, and (v) providing discrete structural pathways (interprism) for
circumferential cracks to propagate normal to the surface for easy arrest by the
underlying dentin layer, hence containing damage locally. These results indicate the
potential to use anisotropy of the individual layers as a means for design optimization of hierarchically structured material systems for dissipative armor,” (Wang
et al. 2009 ).
The next intriguing topic on fi sh scale biomechanics is related to poorly investigated interlocking mechanisms between scales as well as between interfaces of different layers. Bruet ( 2008 ) observed the interfaces between layers in P. senegalus
scales to be exceedingly strong and tough, e.g. the ganoin-dentin junction was able
to arrest microcracks. Localized fractures within the brittle ganoin layer and detachment of fragments of the ganoine layer of the scale was seen, while the ganoindentin junction remains wholly intact; perhaps as a sacrifi cial mechanism. “The
corrugated junction between the layers is expected to lead to spatially heterogenous
stresses and a higher net interfacial compression which could serve to prevent
delamination,” (Bruet 2008 ).
Since 2008, the giant scales of Arapaima gigas a fi sh from the Amazonian region
with a rather prehistorical aspect became the status of subject of scientifi c investigations with regard to materials science and biomineralization. It is known for its large
tough scales which are used in handcrafts and souvenirs (Torres et al. 2008 ).
Arapaima is a giant fi sh measuring over 2 m in length and weighing in at over
100 kg. Their scales of varying degrees of mineralization serve as a dermal armor to
natural predators, including piranhas. These scales are elasmoid and consist of an
elasmodine basal plate of a twisted plywood arrangement of collagen fi bers capped
with different hypermineralized tissues (Meunier and Brito 2004 ; Sire et al. 2009 ;
Torres et al. 2008 ). Scales of A. gigas have a partially mineralized base and well
mineralized limiting layer of hydroxyapatite. Recently, Marc Meyers and coworkers from UC San Diego (Lin et al. 2011 ) published a paper on laminate structure and mechanical properties of A. gigas scales. This work received a large mass
media resonance because of the unique experiments that were carried out in the Lab
using teeth of piranhas as the potential biological enemy of Arapaima. Piranhas use
their famous razor-like teeth to trap skin and muscle in a guillotine-like bite, and
then tear the prey into bits. Meyers and colleagues embedded Arapaima scales in a
soft rubber surface (to mimic the underlying muscle on the fi sh), and attached piranha teeth to an industrial-strength hole punch. When the tooth was pushed into the
scale, it partially penetrated the outer defences, but cracked before it could puncture
the muscle. Here is the clue (Brown 2012 ): the heavily mineralised scales with hard
enamel-like outer layer overlap each other like shingles. Their surface is wrinkled,
too, to allow it to bend without cracking. Collagen fi bers with plywood-like orientation are stacked underneath. This combination of a softer internal architecture and a
strong outer layer determines unique mechanical properties of the construct. This
lets the aquatic animal remain mobile while staying heavily armoured and alive.
5 Materials Design Principles of Fish Scales and Armor
suppression of catastrophic radial surface cracking, and favoring localized circumferential cracking, and (v) providing discrete structural pathways (interprism) for
circumferential cracks to propagate normal to the surface for easy arrest by the
underlying dentin layer, hence containing damage locally. These results indicate the
potential to use anisotropy of the individual layers as a means for design optimization of hierarchically structured material systems for dissipative armor,” (Wang
et al. 2009 ).
The next intriguing topic on fi sh scale biomechanics is related to poorly investigated interlocking mechanisms between scales as well as between interfaces of different layers. Bruet ( 2008 ) observed the interfaces between layers in P. senegalus
scales to be exceedingly strong and tough, e.g. the ganoin-dentin junction was able
to arrest microcracks. Localized fractures within the brittle ganoin layer and detachment of fragments of the ganoine layer of the scale was seen, while the ganoindentin junction remains wholly intact; perhaps as a sacrifi cial mechanism. “The
corrugated junction between the layers is expected to lead to spatially heterogenous
stresses and a higher net interfacial compression which could serve to prevent
delamination,” (Bruet 2008 ).
Since 2008, the giant scales of Arapaima gigas a fi sh from the Amazonian region
with a rather prehistorical aspect became the status of subject of scientifi c investigations with regard to materials science and biomineralization. It is known for its large
tough scales which are used in handcrafts and souvenirs (Torres et al. 2008 ).
Arapaima is a giant fi sh measuring over 2 m in length and weighing in at over
100 kg. Their scales of varying degrees of mineralization serve as a dermal armor to
natural predators, including piranhas. These scales are elasmoid and consist of an
elasmodine basal plate of a twisted plywood arrangement of collagen fi bers capped
with different hypermineralized tissues (Meunier and Brito 2004 ; Sire et al. 2009 ;
Torres et al. 2008 ). Scales of A. gigas have a partially mineralized base and well
mineralized limiting layer of hydroxyapatite. Recently, Marc Meyers and coworkers from UC San Diego (Lin et al. 2011 ) published a paper on laminate structure and mechanical properties of A. gigas scales. This work received a large mass
media resonance because of the unique experiments that were carried out in the Lab
using teeth of piranhas as the potential biological enemy of Arapaima. Piranhas use
their famous razor-like teeth to trap skin and muscle in a guillotine-like bite, and
then tear the prey into bits. Meyers and colleagues embedded Arapaima scales in a
soft rubber surface (to mimic the underlying muscle on the fi sh), and attached piranha teeth to an industrial-strength hole punch. When the tooth was pushed into the
scale, it partially penetrated the outer defences, but cracked before it could puncture
the muscle. Here is the clue (Brown 2012 ): the heavily mineralised scales with hard
enamel-like outer layer overlap each other like shingles. Their surface is wrinkled,
too, to allow it to bend without cracking. Collagen fi bers with plywood-like orientation are stacked underneath. This combination of a softer internal architecture and a
strong outer layer determines unique mechanical properties of the construct. This
lets the aquatic animal remain mobile while staying heavily armoured and alive.
5 Materials Design Principles of Fish Scales and Armor