Size-dependent elastic-inelastic behavior of enamel over millimeter and nanometer length scales

The microstructure of enamel like most biological tissues has a hierarchical structure which determines their mechanical behavior. However, current studies of the mechanical behavior of enamel lack a systematic investigation of these hierarchical length scales. In this study, we performed macroscopic uni-axial compression tests and the spherical indentation with different indenter radii to probe enamel’s elastic/inelastic transition over four hierarchical length scales, namely: ‘bulk enamel’ (mm), ‘multiple-rod’ (10’s µm), intra-rod’ (100’s nm with multiple crystallites) and finally ‘single-crystallite’ (10’s nm with an area of approximately one hydroxyapatite crystallite). The enamel’s elastic/inelastic transitions were observed at 0.4-17GPa depending on the length scale and were compared with the values of synthetic hydroxyapatite crystallites. The elastic limit of a material is important as it provides insights into the deformability of the material before fracture. At the smallest investigated length scale (contact radius ~20nm), elastic limit is followed by plastic deformation. At the largest investigated length scale (contact size ~1mm), only elastic then micro-crack induced response was observed. A map of elastic/inelastic regions of enamel from millimeter to nanometer length scale is presented. Possible underlying mechanisms are also discussed.

Subjects

elastisch-inelastischer Übergang

Mechanische Eigenschaften

Eindruckversuch

Druckversuch

hierarchische Struktur

size-dependent

elastic-inelastic transition

enamel

mechanical properties

nanoindentation

DDC Class

620: Ingenieurwissenschaften

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http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php

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Size_dependent_Elastic_Inelastic_Behavior_of_Enamel_over_Millimeter_and_Nanometer_Length_Scales.pdf

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Size-dependent elastic-inelastic behavior of enamel over millimeter and nanometer length scales