The role of quasi-plasticity in the extreme contact damage tolerance of the stomatopod dactyl club

Abstract

The structure of the stomatopod dactyl club--an ultrafast, hammer-like device used by the animal to shatter hard seashells--offers inspiration for impact-tolerant ceramics. Here, we present the micromechanical principles and related micromechanisms of deformation that impart the club with high impact tolerance. By using depth-sensing nanoindentation with spherical and sharp contact tips in combination with post-indentation residual stress mapping by Raman microspectroscopy, we show that the impact surface region of the dactyl club exhibits a quasi-plastic contact response associated with the interfacial sliding and rotation of fluorapatite nanorods, endowing the club with localized yielding. We also show that the subsurface layers exhibit strain hardening by microchannel densification, which provides additional dissipation of impact energy. Our findings suggest that the club's macroscopic size is below the critical size above which Hertzian brittle cracks are nucleated.

A micro finite-element model for soil behaviour: numerical validation

“…10. Energy dissipation by plastic yielding during a Hertzian contact cycle, E e is the elastic energy and E P is the plastic energy (after Amini et al, 2015) …”

“…Figure 10 shows the distribution of elastic and plastic energy dissipation for the case of a single grain in Hertzian contact. Based on this, Amini et al (2015) recently proposed a plastic dissipated energy index for a single elastic-plastic particle given by the ratio between plastic and total contact energy (i.e. the sum of elastic and plastic energies).…”

A Sinusoidally Architected Helicoidal Biocomposite

“…[20] Additionally, supporting nanomechanical studies revealed the anisotropic stiffness response and quasi-plastic nature of the impact region. [20,21] However, key details regarding the microand nano-structural features and the corresponding mechanical response have yet to be revealed.Here, we uncover a novel ultrastructural design within the impact region of the dactyl club, which exhibits a notable departure from the helicoidal structure found within most crustacean exoskeletons and affords superior mechanical advantages. We also reveal previously unreported structural and mechanical details from this region that not only provide new insights to the design of impact resistant and damage-tolerant composite materials, but also hint at the mechanisms of self-assembly and biomineralization in complex biological architectures.…”

“…[20] Additionally, supporting nanomechanical studies revealed the anisotropic stiffness response and quasi-plastic nature of the impact region. [20,21] However, key details regarding the microand nano-structural features and the corresponding mechanical response have yet to be revealed.…”

Inherent Role of Water in Damage Tolerance of the Prismatic Mineral–Organic Biocomposite in the Shell of Pinna Nobilis

“…Most of the studies focusing on the effect of relative humidity on mechanical behavior of biocomposite materials reported the properties of the entire tissue [12][13][14] or its microstructural sub-domains. [15][16][17] The infl uence of moisture content on mechanical performance of individual components on the submicron scale was never previously described, mainly due to their microscopic size and the lack of appropriate experimental techniques. However, recent advances in nanomechanical characterization technology, that include environmentally controlled nanoindentation, [ 11 ] modulus mapping [18][19][20][21][22][23] and microcantilever bending, [ 24 ] have fi nally provided the ability to access the humidity dependent mechanical properties of extremely small and soft features in biocomposites.…”