In situ optical observation of damage and failure process in adhesively bonded CFRP joints under mixed-mode loading

The effects of mode mixity on microscopic damage and failure process in adhesively bonded carbon fiber reinforced plastic (CFRP) joints were studied by in situ observation. Optical microscopy observation revealed that the damage and failure process were largely affected by the mixed-mode ratio of joints. The whitening of the adhesive resin due to cavitation was observed with an increasing mode I component, whereas the plastic zone length increased with an increasing mode II component. The damage and failure process observed by experiment were correlated with the stress state around the crack tip obtained by finite element analysis. The results indi-cated that the microscopic failure process well reflects the deformation and failure properties of epoxy resin depending on stress triaxiality.

Automated summary

In situ observation was used to study the effects of mode mixity on microscopic damage and failure process in adhesively bonded carbon fiber reinforced plastic (CFRP) joints. The results showed that the damage and failure process were significantly influenced by the mixed-mode ratio of joints. An increasing mode I component led to the whitening of the adhesive resin due to cavitation, whereas an increasing mode II component resulted in an increased plastic zone length. The observed damage and failure process correlated with the stress state around the crack tip obtained by finite element analysis.