Kinetics of channeling cracks in polymeric coatings

These approaches were used to analyze a multi-layer system consisting of a polymeric, colloidal-silica nano-composite layer and a primer layer coating a polycarbonate substrate. The crack growth showed a threshold value of energy-release rate corresponding to about 6.6 J/m2, with a minimum detectable crack velocity of about 3 nm/s. When the energy-release rate was increased to about 25 J/m2, the resultant crack velocity was 10-2 m/s. The channeling cracks in this system exhibited the characteristics of a thermally-activated rupture process, but showed no evidence of fatigue or stress-corrosion cracking under the conditions studied.