Interfibril hydrogen bonding improves the strain-rate response of natural armour

Abstract

<jats:p>Fish scales are laminated composites that consist of plies of unidirectional collagen fibrils with twisted-plywood stacking arrangement. Owing to their composition, the toughness of scales is dependent on the intermolecular bonding within and between the collagen fibrils. Adjusting the extent of this bonding with an appropriate stimulus has implications for the design of next-generation bioinspired flexible armours. In this investigation, scales were exposed to environments of water or a polar solvent (i.e. ethanol) to influence the extent of intermolecular bonding, and their mechanical behaviour was evaluated in uniaxial tension and transverse puncture. Results showed that the resistance to failure of the scales increased with loading rate in both tension and puncture and that the polar solvent treatment increased both the strength and toughness through interpeptide bonding; the largest increase occurred in the puncture resistance of scales from the tail region (a factor of nearly 7×). The increase in strength and damage tolerance with stronger intermolecular bonding is uncommon for structural materials and is a unique characteristic of the low mineral content. Scales from regions of the body with higher mineral content underwent less strengthening, which is most likely the result of interference posed by the mineral crystals to intermolecular bonding. Overall, the results showed that flexible bioinspired composite materials for puncture resistance should enrol constituents and complementary processing that capitalize on interfibril bonds.</jats:p>

Contributions of intermolecular bonding and lubrication to the mechanical behavior of a natural armor

“…As previously highlighted, the relative contributions of interfibrillar sliding and fibril rotation may depend on the free length of the fibers (i.e., the width of the specimens) and that was not considered in the present investigation. Another limitation is that the scale properties were evaluated at a single strain rate and the relative contribution of interpeptide bonds is a function of strain rate [2] . Future studies could address the changes in contributing mechanisms as a function of strain rate.…”

Modulatory role of terminal monomeric flavan‐3‐ol units in the viscoelasticity of dentin

“…After biomodification, an increase in the damping capacity was identified at the microscale level and could indicate that modified dentin displays a higher capacity to dissipate energy during mechanical vibration than unmodified dentin matrix. 57,58 Interfibrillar bonds formed by Trimer-C and Trimer-EC may enable an increase in fibrillar sliding and the conformational flexibility of PAC-protein complexes that, combined with fluid motions throughout interfibrillar spaces of the ECM, induce a more viscous-like behavior of dentin. Conversely, the reduction of the damping capacity observed at the nanoscale could be due to the increase in intermolecular and interfibrillar cross-linking and possible occupation of gap and overlap zones by these bonds.…”

Fish scale inspired structures—a review of materials, manufacturing and models

“…Mechanical properties such as elastic modulus, ultimate tensile strength, strain at failure, modulus of toughness and stiffness were also evaluated by uniaxial tensile testing and transverse puncture testing on C. carpio scales [61]. Here, scales were obtained from near the head, middle and tail region of multiple fish, and then evaluated after being fully hydrated in water or after exposure to a polar solvent (ethanol) to find the effect of the polar solvent on the mechanical properties of the scales.…”