Effects of the marine environment on the interfacial fracture toughness of PVC core sandwich composites

An experimental study was undertaken to investigate the facesheet/core interfacial fracture toughness of E-Glass/Vinylester facesheet, closed-cell polyvinyl chloride (PVC) core, sandwich composites. To determine the effects of a marine environment (temperature and sea-water) on conditioned specimens with a crack present, an interfacial crack was induced prior, as well as subsequent to, 5000 h of elevated temperature (80 °C), elevated temperature and moisture (80 °C, 90%+ relative humidity), and sea-water (submersed) conditioning. The interfacial fracture toughness from room temperature double cantilever beam tests for each environmental condition was then compared using the critical strain energy release rate, G_C. The G_C was reduced considerably (greater than 50%) in specimens submerged in sea-water, and significantly (approximately 90%) due to 5000 h of the ‘hot/wet’ and hot/dry exposure. Results showed that elevated temperature exposure contributes greatest to the PVC core degradation, whereas sea-water exposure mostly degrades the facesheet/core interface. Exposure to elevated temperatures, along with inducing cracks between the facesheet and a PVC core degraded by elevated temperature exposure, appear to be the most detrimental to interfacial fracture toughness.