Unraveling non-uniform strain-induced crystallization near a crack tip in natural rubber

Strain-induced crystallization (SIC) in natural rubber near crack tips significantly enhances crack growth resistance, but understanding the interplay between local strain field and crystallization remains challenging due to confined and heterogeneous characteristics. Using micro-scale digital image correlation and scanning wide-angle X-ray diffraction (with a narrow 10 µm square beam), this study maps local strain tensor properties and SIC in the vicinity of the crack tip and its peripheral zone (approximately 3 x 1 mm area). The analysis reveals a significant correlation between these properties, with the spatial distribution of the local principal strain axis influencing crystal orientation. Crucially, the maximum tensile component in the tensor of local principal strains predominantly dictates local crystallinity, irrespective of strain biaxiality. This finding paves the way for predicting crystallinity distribution using solely strain field data, offering valuable insights into the role of SIC in enhancing the crack growth resistance of natural rubber.