Moisture Effects on Mixed-Mode Delamination of Carbon/Epoxy Composites

Abstract

An investigation of the effects of moisture on fracture and fatigue performance of a carbon/epoxy composite is presented, including delamination toughness and growth for a range of mode mixities from mode I to mode II loading. Experimental static and fatigue tests were carried out on composite specimens. The static test results show that exposure to moisture led to a decrease in delamination toughness under mode II and mixed-mode I/II loading while enhancing delamination toughness under mode I loading. These results are compared with existing mixed-mode fracture criterion to determine which model better predicts mixed-mode delamination toughness for both dry and moisture conditioned specimens. Fatigue tests demonstrate that moisture has an adverse effect on delamination resistance of the composite under loadings of all mode mixities. An increase in delamination growth rate for exposed specimens is also observed for all mode mixities. Existing delamination growth rate models are compared with experimental values to determine the most suitable model for predicting delamination growth rates for these specimens.