Fatigue crack growth behavior and mechanism of closed-cell PVC foam

Abstract

The applicability of linear-elastic fracture mechanics parameters (DK and Kmax), elastic–plastic fracture mechanics parameter (DJ), 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 ¼ 0.1 and 0.4) on FCGs was observed when the DK, Kmax and DJ were used as fracture mechanics parameters. As a fracture mechanics parameter that combines DK and Kmax, the K* successfully characterized FCGs (da/dN )a tR ¼ 0.1 and 0.4. While, a time-dependent fracture mechanics parameter (C*) successfully correlated da/dt of creep crack growth (CCG) test, but it failed to correlate da/dt of FCG tests. The FCGs at both R ¼ 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 cracktip 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. POLYM. ENG. SCI., 53:1719–1727, 2013. a 2012 Society of Plastics Engineers