In-situ observation of microscopic damage in adhesively bonded CFRP joints under mode I and mode II loading

摘要

Microscopic failure mechanisms in adhesively bonded joints of carbon fiber reinforced polymer (CFRP) structures were studied, and in-situ observation during fracture toughness tests under mode I and mode II loading were carried out. Strain in the adhesive layer was quantitatively evaluated by applying the digital image correlation (DIC) method to micrographs. Strain concentration was observed along the CFRP/adhesive interface under mode I loading. On the other hand, strain concentration and microcracks around the polyester carrier was observed under mode II loading. The macroscopic crack growth occurred due to the coalescing of microcracks under mode II loading. The maximum principal strain in adhesive resin under mode II loading at the onset of crack growth was significantly larger than that under mode I loading. The effects of distance from specimen edge on the crack growth behavior were also studied using the X-ray computed tomography.