Fatigue Crack Propagation in Polyvinylchloride and Polyethersulfone Polymer Foams

Crack growth in cross-linked polyvinylchloride and thermoplastic polyethersulfone foams under mode I fatigue cycling has been experimentally examined. Polyvinylchloride foams of densities ranging from 45 to 100 kg/m3 and polyethersulfone foams of densities ranging from 60 to 130 kg/m3 were considered. All cyclic tests employed the sandwich double cantilever beam test specimen. The test results revealed that crack growth rate (da/dN) compared at a constant cyclic energy release rate (ΔG) decreased with increasing density of the foam. The crack propagation rates in low-density polyethersulfone foams were much less than in polyvinylchloride foams of similar density. The crack growth rate in the high-density polyethersulfone foam was highly dependent on the loading R-ratio. The crack front in the low-density polyethersulfone foam displayed marked deviations from a straight shape, where the edge regions propagated faster than the center of the specimen. All polyvinylchloride foams and high-density polyethersulfone foam displayed straight crack fronts.