Microstructure and nanomechanical properties of the exoskeleton of an ironclad beetle ().

This study examined natural composite structures within the remarkably strong exoskeleton of the southwestern ironclad beetle (). Structural and nanomechanical analyses revealed that the exoskeleton's extraordinary resistance to external forces is provided by its exceptional thickness and multi-layered structure, in which each layer performed a distinct function. In detail, the epicuticle, the outmost layer, comprised 3%-5% of the overall thickness with reduced Young's moduli of 2.

Quantitative Analysis of Tissue Damage Evolution in Porcine Liver With Interrupted Mechanical Testing Under Tension, Compression, and Shear.

In this study, the damage evolution of liver tissue was quantified at the microstructural level under tensile, compression, and shear loading conditions using an interrupted mechanical testing method. To capture the internal microstructural changes in response to global deformation, the tissue samples were loaded to different strain levels and chemically fixed to permanently preserve the deformed tissue geometry. Tissue microstructural alterations were analyzed to quantify the accumulated damages, with damage-related parameters such as number density, area fraction, mean area, and mean nearest neighbor distance (NND).

The geometric effects of a woodpecker's hyoid apparatus for stress wave mitigation.

In this study a woodpecker's hyoid apparatus was characterized to determine its impact mitigation mechanism using finite element (FE) analysis. The woodpecker's hyoid apparatus, comprising bone and muscle, has a unique geometry compared to those of other birds. The hyoid starts at the beak tip, surrounds the woodpecker's skull, and ends at the upper beak/front head intersection while being surrounded by muscle along the whole length.

Hierarchical multiscale structure-property relationships of the red-bellied woodpecker (Melanerpes carolinus) beak.

We experimentally studied beaks of the red-bellied woodpecker to elucidate the hierarchical multiscale structure-property relationships. At the macroscale, the beak comprises three structural layers: an outer rhamphotheca layer (keratin sheath), a middle foam layer and an inner bony layer. The area fraction of each layer changes along the length of the beak giving rise to a varying constitutive behaviour similar to functionally graded materials.

The effects of water and microstructure on the mechanical properties of bighorn sheep (Ovis canadensis) horn keratin.

The function of the bighorn sheep horn prompted quantification of the various parametric effects important to the microstructure and mechanical property relationships of this horn. These parameters included analysis of the stress-state dependence with the horn keratin tested under tension and compression, the anisotropy of the material structure and mechanical behavior, the spatial location along the horn, and the wet-dry horn behavior. The mechanical properties of interest were the elastic moduli, yield strength, ultimate strength, failure strain and hardness.