An analytical hierarchical model explaining the robustness and flaw-tolerance of the interlocking barb-barbule structure of bird feathers

Chen, Qiang; Gorb, Stanislav N.; Kovalev, Alexander; Li, Zhi Yong; Pugno, Nicola

doi:10.1209/0295-5075/116/24001

Cited by 8 publications

(22 citation statements)

References 10 publications

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“…As barbules play important roles in maintaining the mechanical integrity of flight feathers (e.g. Chen et al 2016, Sullivan et al 2017, it is possible that a reduction in the number of barbules could result in lower mechanical integrity, causing the apical sections of the barbs to 'bend together' or break off at the edge of the vane and reducing its surface area (Fig. 1).…”

Section: Data Collectionmentioning

confidence: 99%

The meaning of purely structural colour: white plumage reflectance indicates feather condition

Laczi

Balogh

Nardou

et al. 2020

Ibis

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White plumage areas are widespread among birds but the mechanisms generating individual differences in white feather reflectance are poorly known. Additionally, the proximate mechanisms of within‐season feather colour changes in general are also poorly known. Here we explored within‐individual changes in macrostructure and reflectance of the white wing‐patch of female Collared Flycatchers Ficedula albicollis using data from three stages within a breeding season. Changes in brightness and UV chroma were related to changes in the neatness and size of reflective surfaces, respectively. This suggests that white feather reflectance traits may act as indicators of feather intactness and preening activity.

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Section: Data Collectionmentioning

confidence: 99%

The meaning of purely structural colour: white plumage reflectance indicates feather condition

Laczi

Balogh

Nardou

et al. 2020

Ibis

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“…In the delamination, the barb is regarded as a classical cantilever with one end fixed. Here, different from the literature [2] where the barb was modeled as a small-deformation beam, the barb here is treated as a largedeformation beam. Considering the coupling deformations of the barb and barbule, for an arbitrary point (X , Y ) of the barb locating between the ith and (i + 1)th interlocking barbules, the moment equilibrium at the arbitrary point is expressed as…”

Section: Delamination Theory Of Two Neighboring Barbsmentioning

confidence: 99%

“…(2) j = l (2) f j /D (2) ,S = S/l (1) , δX FE = δX FE /l (1) ,X = X/l (1) ,X B, j = X B, j /l (1) , Eq. ( 12) is re-expressed as…”

Section: Delamination Theory Of Two Neighboring Barbsmentioning

confidence: 99%

“…The two types of barbules interlock with each other to form a feather vane through the distributed hooklets on hook barbules, see Fig. 1 [1,2], and this makes the feather vane flexibly deformable. However, literature on the interlocking mechanics of the interesting barb-barbule structure in feathers was not as well reported as other tough natural structures (e.g., nacre [3,4] and beetle's wing [5]).…”

Section: Introductionmentioning

confidence: 99%

“…Sullivan et al proposed an interlocking mechanism of the barbs and studied in-plane adhesion and stiffness of barbules, and reported that the interlocking adherence enabled a more robust structure due to minimized barb torsion [18,19]. Recently, basing on beam theories, the authors developed a friction-based hierarchical interlocking barb-barbule model to explain the flaw-tolerant ability in delaminating two barbs [2]. Although these studies have revealed its interlocking adherent robust and flawtolerant mechanisms of the barb-barbule structure, they did not discuss the rotation of the barb-barbule joint in the barb delamination process.…”

Section: Introductionmentioning

confidence: 99%

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The rotation toughening mechanism of barb–barbule joint in the barb delamination of feathers

Chen

Pugno

2019

Acta Mech

Self Cite

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The barb-barbule structure branching from a feather shaft is a basic unit of a bird feather, and the structure is intricately organized to form the feather vane, which plays an important role in keeping the feather's integrity during bird flight. In this paper, by coupling nonlinear large deformations of the barb and barbule, an analytical model of delaminating two neighboring barbs on the basis of critical-friction detaching criteria is developed. Considering the rotation and non-rotation of barb-barbule joints in the delamination, a rotatable model (LargeRM) and a non-rotatable model (LargeNRM) are treated to explain the rotation's contribution to toughening the feather vane. The results show that the predicted interlocking forces of un-detached barbules in the two models were linearly distributed during the delamination. Due to the rotatable barb-barbule joint, the critical detaching force and the elastic strain energy of the two neighboring barbs in the LargeRM are greater than those in the LargeNRM, and this indicates that the rotatable barb-barbule joint could enhance the inplane delaminating toughness of the feather vane. The present model reveals the nonlinear barb delamination behavior and explains the rotation toughening mechanism of the barb-barbule joint in the barb delamination and further is used to design new bio-inspired interlocking materials, e.g., the feather-inspired Velcro fastener.

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The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

Deng

Kovalev

Rajabi

et al. 2021

Sci Nat

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The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.

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An analytical hierarchical model explaining the robustness and flaw-tolerance of the interlocking barb-barbule structure of bird feathers

Cited by 8 publications

References 10 publications

The meaning of purely structural colour: white plumage reflectance indicates feather condition

The meaning of purely structural colour: white plumage reflectance indicates feather condition

The rotation toughening mechanism of barb–barbule joint in the barb delamination of feathers

The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

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