Fatigue Crack Growth Behavior and Mechanism of Closed-cell PVC Foam

摘要

The applicability of linear-elastic fracture mechanics parameters (AK and K_(max)), elastic-plastic fracture mechanics parameter (AJ), and time-dependent fracture mechanics parameter (C*) to characterize fatigue crack growth (FCG) rate of closed-cell polyvinyl chloride foam was investigated in the present work. The effect of stress ratios (R = 0.1 and 0.4) on FCGs was observed when the AK, K_(max) and AJ were used as fracture mechanics parameters. As a fracture mechanics parameter that combines ΔK and K_(max), the K~* successfully characterized FCGs (dNdN) at R = 0.1 and 0.4. While, a time-dependent fracture mechanics parameter (C~*) successfully correlated dNdt of creep crack growth (CCG) test, but it failed to correlate dNdt of FCG tests. The FCGs at both R = 0.1 and 0.4 were cyclic dependent, while the CCG was time dependent. For cyclic-dependent crack growth, the interaction between polymer-chain scission and small scale crack-tip blunting was the main mechanism, whereas the interaction between polymer-chain pullout and large scale crack-tip blunting dominated fracture process for time-dependent crack growth.