Crack thickness

Macroscopic
cracks do not appear as a result of an ideal separation of two adjacent atomic
layers. Just the opposite, cracks appear as a result of the development of
multiple micro-cracks triggered by the massive breakage of atomic bonds. The microcracking
and the bond breakage are not confined to two neighbor atomic planes: the
process involves thousands atomic planes within the representative characteristic
volume of size h. This size defines the width (not the lenth) of the damage
localization zone and it can be called the crack thickness. The knowledge of
the crack thickness is especially important for modeling crack propagation. In
the attached three notes I calculate the crack thickness for natural rubber: h
~0.2 mm; DH36 steel: h ~10 μm; and plain concrete: h ~2 cm.