Damage mechanisms in glass/epoxy composites subjected to simultaneous humidity and freeze-thaw cycles

Abstract

The damage mechanism in a composite plate with an edge notch influenced by water freezing and subjected to bending loading is investigated using Scanning Electron Microscopy images. The microstructure of the composite plate around the notch tip induced by freeze-thaw cycles is compared to dry specimens and showed a change in shape of the notch in micro-scale as well as introducing surface minor damage after conditioning. Moreover, the fracture surface of specimens, conditioned for 10, 25, 75 and 100 cycles of freeze-thaw, after bending experiments is analyzed. The results show that the different damage modes involved in the final failure are concentrated at the notch tip as the number of cycles is increased. The higher contribution of delamination in failure when the freeze-thaw cycles are increased can explain the changes in load-displacement curves after conditioning such as decrease in load corresponding to onset of nonlinearity and reduction of maximum load.