55 research outputs found
Mechanical behavior of biomimetic surface scales
Examining the evolutionary response of diverse biological species to counter the existential threats from hostile environmental and predatory landscape can shed light on the principles of protective system design. In this context, dermal scales, prevalent across biological groups imply their versatility in boosting survivability and providing multifunctional advantages for the species. Here, we investigate the nonlinear mechanical effects of biomimetic scale-like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial distribution of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking the well-known material level complexities. Our study shows biomimetic sclaes are capable of exhibiting an additional higher spatial scale of complex mechanical effects in addition to those at the lower meso level often due to the topology of constituents and the even lower constituent level which are often of purely material origin
Frictional Effects in Biomimetic Scales Engagement
Scales engagement can contribute significantly to nonlinear bending behavior
of elastic substrates with rigid biomimetic scales. In this letter, we
investigate the role of friction in modulating the nonlinearity that arises due
to self-contact of scales through an analytical investigation. We model the
friction as dry Coulomb type friction between rigid links and the substrate is
taken to be linear elastic. Our results reveal that frictional effects give
rise to two possible locking mechanisms, namely static friction lock and
kinetic friction lock. These locks arise due to a combination of interfacial
behavior and geometry. In addition to these extremes, the frictional behavior
is found to increase stiffness of the structure. This dual nature of friction
which influences both system operation and its terminal limit results in the
maximum relative frictional work to lie at intermediate friction coefficients
and not at the extremes of frictional limits.Comment: 4 pages, 4 figure
Material-Geometry Interplay in Damping of Biomimetic Scale Beams
Biomimetic scale-covered substrates are architected meta-structures
exhibiting fascinating emergent nonlinearities via the geometry of collective
scales contacts. In spite of much progress in understanding their elastic
nonlinearity, their dissipative behavior arising from scales sliding is
relatively uninvestigated in the dynamic regime. Recently discovered is the
phenomena of viscous emergence, where dry Coulomb friction between scales can
lead to apparent viscous damping behavior of the overall multi-material
substrate. In contrast to this structural dissipation, material dissipation
common in many polymers has never been considered, especially synergestically
with geometrical factors. This is addressed here for the first time, where
material visco-elasticity is introduced via a simple Kelvin-Voigt model for
brevity and clarity. The results contrast the two damping sources in these
architectured systems: material viscoelasticity, and geometrical frictional
scales contact. It is discovered that although topically similar in effective
damping, viscoelsatic damping follows a different damping envelope than dry
friction, including starkly different effects on damping symmetry and specific
damping capacity.Comment: 5 figures, 7 page
Slender Origami with Complex 3D Folding Shapes
One-dimensional slender bodies can be deformed or shaped into spatially
complex curves relatively easily due to their inherent compliance. However,
traditional methods of fabricating complex spatial shapes are cumbersome, prone
to error accumulation and not amenable to elegant programmability. In this
letter, we introduce a one-dimensional origami based on attaching Miura-ori
that can fold into various programmed two or three-dimensional shapes. We study
the out-of-plane displacement characteristics of this origami and demonstrate
with examples, design of slender bodies that conform to programmed complex
spatial curves. Our study provides a new, accurate, and single actuation
solution of shape programmability
SpiderWeb honeycombs
A new class of hierarchical fractal-like honeycombs inspired by the topology of the “spiderweb” were introduced and their small and large deformations were investigated analytically, numerically, and experimentally. Small deformation elasticity results show that the isotropic in-plane elastic moduli (Young’s modulus and Poisson’s ratio) of the structures can be controlled over several orders of magnitude by tuning dimension ratios in the hierarchical pattern of spiderweb, and the response can vary from bending to stretching dominated. In large deformations, spiderweb hierarchy postpones the onset of instability compared to stretching dominated triangular honeycomb (which is indeed a special case of the proposed spiderweb honeycomb) and exhibits hardening behavior due to geometrical nonlinearity. Furthermore, simple geometrical arguments were obtained for large deformation effective Poisson’s ratio of first-order spiderweb honeycombs, which show good agreement with numerical and experimental results. Spiderweb honeycombs exhibit auxetic behavior depending on the nondimensional geometrical ratio of spiderweb
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