Effect of temperature on pure modes I and II fracture behavior of composite bonded joints

The influence of the temperature on pure modes I and II fracture behavior of carbon-epoxy composite bonded joints was investigated. The joints were exposed to a specific range of temperatures during three months in order to simulate long exposure time. Three temperatures were studied: 0 °C, 25 °C (room condition) and 50 °C. The limit temperatures were defined in order to be representative of the extreme climatic conditions to which structures can be exposed in winter and summer in Portugal. Similar fracture energies were obtained at 0 °C and 25 °C under mode I loading, but an abrupt decrease was observed at 50 °C. Regarding mode II, the fracture energy was only slightly affected by temperature. A numerical study using a cohesive zone model considering trapezoidal laws was also performed to evaluate the temperature effect on the cohesive parameters. For mode I loading some influence was observed on those parameters contrasting to which happened under pure mode II whose parameters were almost unaffected in the range of temperatures studied.