Mechanically Modulated Strain-Induced Crystallization around Crack Tips in Nanofiller-Reinforced Elastomers

Area of Science:

• Materials Science
• Polymer Science
• Mechanics of Materials

Background:

• Understanding material response to extreme deformation is key for soft material design.
• Elastomers with nanofillers and strain-induced crystallization (SIC) exhibit complex behaviors near crack tips.

Purpose of the Study:

• To investigate the interplay between nanofiller reinforcement and strain-induced crystallization (SIC) near crack tips in elastomers.
• To map local strain and crystallinity fields and understand their relationship with deformation and filler effects.

Main Methods:

• Integration of microscale digital image correlation with scanning wide-angle X-ray diffraction.
• Analysis of over 15,000 diffraction patterns to map strain and crystallinity fields.
• Investigation of material behavior near crack tips under extreme local deformation.

Main Results:

• Nanofillers expand the SIC-active zone by nearly an order of magnitude and reduce crystallization onset strain from 130% to 65%.
• Strain amplification by fillers diminishes near crack tips, indicating a mechanical compensation effect.
• A dual-slope strain singularity linked to crystallinity gradients was identified, with crystallites acting as in situ reinforcements.

Conclusions:

• Strain-induced crystallization (SIC) generated crystallites mitigate strain concentrations and enhance damage tolerance in filled elastomers.
• The study provides mechanistic insights into SIC-driven toughening in elastomers.
• Findings offer guiding principles for designing soft materials with superior mechanical robustness.