Rate-dependent damage zone leads to micro-stick-slip instability in peeling of soft polymer networks
Phys. Rev. E 114, 055401 – Published 2 November, 2026
DOI: https://doi.org/10.1103/8p56-fy59
Abstract
Adhesive failure of soft polymer networks underpins the mechanical integrity of technologies ranging from packaging to electronics. Yet predictive descriptions of this behavior remain limited because the two main sources of energy dissipation at the peel front, friction and damage, are coupled in ways that are unknown. In prior work, we showed that the damage contribution to the adherence energy is intrinsically rate dependent [A. Arrowood et al., Proc. Natl. Acad. Sci. USA 122, e2509322122 (2025)], challenging viscoelastic fracture theories that treat it as constant. Here we provide further evidence for this picture by identifying a micro-stick-slip instability that emerges from this rate dependence. Using soft acrylic networks labeled with fluorogenic mechanophores, we correlate peel-front kinematics with molecular damage and show that, even under globally steady peeling, the crack front can alternate between a bulged, highly deformed, highly damaged state and a rounded, weakly deformed, weakly damaged state. The onset of this instability is governed by the network relaxation time, and thus by chemical composition and glass transition temperature, whereas the slip speed is the imposed peel speed and the crack-advance length remains nearly constant at 0.26 mm 0.04. Unlike classical stick-slip, which produces large force oscillations and centimeter-scale crack jumps, this micro-stick-slip instability generates only weak force fluctuations and instead reflects localized weakening within the damage zone. Overall, our results reveal a direct coupling between interfacial stress transfer and molecular damage at the peel front, motivating nested cohesive-zone models that incorporate rate-dependent molecular damage to predict adhesive fracture.
