Analysis of the dissipative mechanisms in metal-elastomer interfaces

Remarkable toughnesses have been reported for metal-elastomer interfaces in stretchable electronics and attributed to surface roughness-induced fibrillation. Interestingly, this micro-mechanism was also observed for PDMS, known for its hyperelastic and thus non-dissipative material behavior. Here, the energy dissipation origin is elucidated by a thorough multi-scale experimental analysis of PDMS-copper delamination, for two distinct mode-mixities and surface roughnesses. The fracture process zone was observed by in situ and post-mortem optical and electron microscopy, and compared to cohesive-zone finite elements simulations: The PDMS deformation is indeed (predominantly) reversible and most energy is dissipated by release of elastically stored energy upon fibril fracture.