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

Abstract

The applicability of linear-elastic fracture mechanics parameters (ΔK and Kmax), elastic-plastic fracture mechanics parameter (ΔJ), 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 ΔK, Kmax and ΔJ were used as fracture mechanics parameters. As a fracture mechanics parameter that combines ΔK and Kmax, the K* successfully characterized FCGs (da/dN) at R = 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 = 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. Copyright © 2012 Society of Plastics Engineers.