Experimental investigation of mixed mode fracture toughness of glass fiber/epoxy laminates with sea water absorption

Degradation of composites properties with water absorption is a severe threat to its application in marine structures and humid environments. Real life composite structures often work under mixed mode loading. In this paper, Glass fiber composite has been investigated for the influence of sea water aging on the fracture toughness under mixed mode loading. Glass fiber/epoxy specimens were immersed for 21 and 35 days in sea water. Controlled mixed mode loading was applied using mixed mode bending fixture. Dry and moisture-saturated specimens were tested for fracture toughness over the room temperature by varying lever length of MMB apparatus. Under mixed mode loading the strain-energy release rate decreased with increase in moisture content. The approximate decrease in fracture toughness was observed 31% and 48.55%, respectively, for 21 and 35 days specimens as compared with dry specimen. Scanning electron microscope analysis revealed interfacial debonding to be leading failure mechanism, representing a strong effect of sea water degradation on fracture toughness results.

Automated summary

The degradation of composite properties due to water absorption poses a severe threat to their application in marine structures and humid environments. Research shows that glass fiber composite materials exhibit significantly reduced fracture toughness under mixed mode loading after exposure to sea water aging, with interfacial debonding identified as a leading failure mechanism.