Crack propagation resistance of slide-ring gels. (24th October 2019) - Liu, Chang
Abstract: The crack propagation behavior of pre-cut slide-ring (SR) gels with movable cross-links is investigated and compared to that of fixed cross-link (FC) gels under uniaxial stretching at a constant speed. Two fracture stages with 20-fold difference in crack velocity are observed for both SR and FC gels. At the beginning, the crack propagates slowly, and the crack propagation resistance is in good accordance with the evaluation based on tearing modulus T r, the initial slope of J -integral – crack tip opening displacement (CTOD) curve. Higher T r and slower crack velocity are observed in SR gels compared to FC gels with similar modulus. Moreover, T r decreases and crack velocity increases with increasing modulus (cross-linking density) for FC gels, whilst both parameters are modulus-independent for SR gels. This means that the slow mode crack propagation resistance of SR gels is dominated by the sliding movement of cross-links instead of the cross-linking density. However, as the strain energy input exceeds a critical value, crack accelerates abruptly and overtakes the sliding dynamics of the cross-links, thus the fracture behavior of SR gels resembles that of FC gels. Our results have revealed the strong correlation between the cross-link mobility and crack propagation resistance of SR gels. Graphical abstract: Image 10330 Highlights: Tearing modulus T r obtained via J -integral – CTOD method is for the first time used to estimate crack propagation resistance of gel materials. Sliding of cross-links improves the crack propagation resistance of slide-ring (SR) gels. Crack propagation behavior of SR gels changes from modulus-independent to modulus-dependent when the sliding of cross-links cannot catch up with the opening of crack tip.