Elsevier

Materials Letters

Volume 264, 1 April 2020, 127296
Materials Letters

A high toughness and light weight armor structure bioinspired design based on a bovine hoof wall

https://doi.org/10.1016/j.matlet.2020.127296Get rights and content

Highlights

  • Mechanical properties and microstructure of the bovine hoof wall have been studied.

  • A kind of special structural model has been proposed.

  • Three dimension printing technology has been used to fabricate the model.

  • This structural model has a high potential to improve the mechanical properties of materials.

Abstract

Mechanical properties and microstructure of the bovine hoof wall have been studied. The reduced modulus and hardness of the transverse and the longitudinal specimens decrease from the outside to the inside, and reach a peak of 4.69 GPa and 0.15 GPa, respectively. The further work reveals that the enhancement mechanism is the lamellar structure and fiber-refined mode. In addition, a kind of structural model is designed and fabricated by three-dimensional printing technology, whose performance is improved by 55%. We hope this work can provide ideas for a new high-toughness and light-weight armor design.

Introduction

Keratin is one of the most common and hardest natural structural materials [1], [2]. The excellent energy absorption capacity of the keratin tissues can protect the body from the impact during undergoing an extreme load [3]. In the battle between bighorn sheep, their horns bear a peak force of 34 N/kg which is equivalent to the force generated by a car collision at 30 mph (33 N/kg) [4]. An unshod equine hoof reaches a peak ground reacting force of 16.1 N/kg when trotting at 4 m/s on an asphalt surface [5]. Compared with the equine hoof, the bovine has considerable weight, smaller contact area, so their hoof walls also need to bear huge impact.

Nowadays, biomimetic technology is becoming a kind of popular and practical method providing novel ideas for new designs. The three-dimensional (3D) printing technology is a great choice. It can not only achieve any irregular geometric shape with complex architectures [6], but also can print biological tissue with the bioink [7] and multi-materials [8] at the same time. Thus, the use of biomimetic design principles and 3D printing tool has the potential to develop a new structural and functional material.

In this study, we investigate the microstructure and mechanical properties of the bovine hoof wall, and design a new structural model based on it. Then, the mechanical properties of the specimens fabricated by 3D printing are examined. We hope our new design work can make some contributions for the new biomimetic material design.

Section snippets

Materials and experimental

The fresh bovine hooves were acquired from a local slaughterhouse (Changsha, China). The hooves were carefully washed and disinfected before stored in a freezer at −10 ℃. Each specimen was carefully cut and protected. Specially, the nanoindentation specimens were embedded by the epoxy resin and the surfaces were polished by sandpapers.

According to ISO 13586-2018, the three-point-bending specimen (SENB, L60 mm × W12 mm × H6 mm) was designed for fracture toughness test. The specimens were thick

Results and discussion

As shown in Fig. 1a, the indentation specimens are chosen the part near the growth line because the mechanical properties were best [9]. The specimens in which the surfaces are normal or parallel to the tubular axis are called transverse (TD) or longitudinal (LD) specimens, respectively. Fig. 1b illustrates the typical nanoindentation P-h curve which can be described as loading – pressure maintaining – unloading process. The reduced modulus (Er) and hardness (H) can be calculated as Er

Conclusions

Mechanical properties and microstructure of the bovine hoof wall have been studied. The nanoindentation test shows that the reduced modulus and hardness of the bovine hoof wall decrease from the outside to the inside and reach a peak of 4.69 GPa and 0.15 GPa. Fracture toughness result of the fabricated specimens shows that this kind of structure can obviously improve the strength-to-volume ratio, and it has a 39% and 55% performance improvement for KIC and GIC, respectively. This structural

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was financially supported by Scientific and technological innovation projects of Hunan Province, China (No. 2017GK2292), and National Natural Science of China (No. 51771231) and by State Key Laboratory of Powder Metallurgy, Central South University (No. 20181106).

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  • Hierarchical modeling of elastic moduli of equine hoof wall

    2022, Journal of the Mechanical Behavior of Biomedical Materials
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    Keratin is a tough and strong biological material present in a variety of animal parts, including the hoof, nail, horn, skin, beak, fish teeth, and so on [7,8]. A plethora of researchers have followed the protective function of keratin-made body parts to develop additively manufactured composites [9–11]. Recent studies on biomimetic composites inspired from hooves [12], horns [8,13], beaks [14,15] and turtle shells [16,17] have shown promising energy absorption characteristics.

  • Engineering with keratin: A functional material and a source of bioinspiration

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    Several researchers have also explored the characteristic tubular structures found in hooves. Wang et al. (2020a) 3D printed simplified tubular arrangements based on bovine hooves (Wang et al., 2020a). The tubules were modeled as hollow hexagonal prisms with varying angles that are inspired by the different angles of the intertubular layers found in the hoof.

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