On the relationship between indentation hardness and modulus, and the damage resistance of biological materials

Abstract

Instrumented indentation is a widespread tool for characterising the mechanical properties of biological materials. Here, we show that the ratio between indentation hardness and modulus is approximately constant in biological materials. A simple elastic-plastic series deformation model is employed to rationalise part of this correlation, and criteria for a meaningful comparison of indentation hardness across biological materials are proposed. The ratio between indentation hardness and modulus emerges as the key parameter characterising the relative amount of irreversible deformation during indentation. Despite their comparatively high hardness to modulus ratio, biological materials are susceptible to quasiplastic deformation, due to their high toughness: quasi-plastic deformation is hence hypothesised to be a frequent yet poorly understood phenomenon, highlighting an important area of future research.

Correlation between theoretical and experimental hardness, elastic modulus of discarded aluminium piston reinforced with zirconium diboride and snail shells

“…Indentation experiments have been performed for measurement of hardness. A significant improvement on indentation equipment keeps increasing in order to improve measurement accuracy [13][14][15][16][17][18]. Hardness is reported as complex parameter which involves elasticity and plasticity governed by intrinsic properties such as bond strength, cohesive energy and crystal structure [19].…”

“…However, hardness cannot be quantitatively described by shear and bulk moduli but can be used to estimate the elastic modulus of composites with various weight percentages (wt%) of composites [19]. Labonte et al [18] reported that indentation hardness is a hybrid measure of a material resistance to irreversible and reversible deformation, and a change in indentation modulus will also affect indentation hardness.…”

Investigating the mechanical behavior of hydroxyapatite-reduced graphene oxide nanocomposite under different loading rates

“…One of the mechanical properties indicators of materials is their behavior against the variable loads applied to the materials at varying rates. Indentation (micro and nano) is one of the methods to obtain the mechanical properties (hardness, elastic modulus, and fracture toughness) of ceramics, which is performed by various indenters such as Vickers and Berkovich indenters [26][27][28][29][30][31][32][33].…”

The interrelationship of microstructure and hardness of human coronal dentin using reference point indentation technique and micro-Raman spectroscopy

“…Young’s modulus [8], thin-film bond strength [9] and shear bond strength [10]. Hardness can also be determined by micro- and nano-indentation techniques [8, 10, 11]. However, reported hardness values vary, which may be due to the innate variability of human teeth and/or testing methods.…”