Relationship of Local Strain-Field and shape of Crack-tip in the Dynamic Crack of Filled Elastomers

The correlation between the crack-tip shape and local strain-field in the dynamic crack with both subsonic (V < C_s) and supersonic (V < C_s) motion of filled elastomers is investigated, where V and C_s are crack-growth rates and shear wave speed. The shape of the crack-tip is characterized by the deviation from the parabolic shape (δ) and the opening displacement (CTOD). The strain-field around the crack-tip is calculated by the two-dimensional digital image correlation technique (DIC) on the basis of the speckle images captured by a high-speed camera. The vertical strain field (e_yy) near the crack-tip can be characterized by the relation e_yy ~ (1/r)^α, known as a crack-tip singularity. We discuss the correlation between the features of the local strain field (α and strain field distribution) and those of the crack-tip shape (δ and CTOD).