Damage characterization and fatigue modeling of CFRP subjected to cyclic loading

Fatigue damage evolution in CFRP is characterized by variation of local transverse strain from digital image correlation (un-notched) and temperature variation from infrared thermography (notched). The damage evolves over 2-3 stages. Matrix cracks and fiber matrix debonding are observed in +/- 45 degrees, 90 degrees and 0 degrees plies in stage I. Fiber fracture is observed in 0 degrees plies only in stage II of the un-notched specimen. It is present even in stage I for notched specimens. In notched specimens, extensive fiber fracture is observed in -45 degrees, 90 degrees and 0 degrees plies in stage II due to higher local stresses. Fiber fracture causes a larger rate of increase in local temperature. A three parameter cumulative damage model is used for predicting the damage evolution and fatigue life. Predictions were good for tension-compression tests in unnotched specimens, but inadequate for compression-compression tests. While using temperature for damage characterization in notched specimens, additional parametrization is required.