The effect of mode II fatigue crack growth rate on the fractographic features of CFRP composite laminates
An acoustic emission and scanning electron microscopy analysis
Reza Mohammadi (Amirkabir University of Technology)
Mehdi Ahmadi Ahmadi Najafabadi (Amirkabir University of Technology)
Hamed Saghafi (Amirkabir University of Technology, Tafresh University)
M Saeedifar (TU Delft - Structural Integrity & Composites)
Dimitrios Zarouchas (TU Delft - Structural Integrity & Composites)
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Abstract
The present study is focused on the characterization of the fatigue damage features in carbon/epoxy laminates under mode-II loading conditions. To this aim, a sinusoidal cyclic load was applied to the End-Notched Flexural (ENF) specimens and the fatigue behavior of specimens was investigated. Scanning Electron Microscope (SEM) was used to identify the damage features on the fracture surface, i.e. fiber imprints, cusps, roller cusps, and striations. It was found that the fatigue damage features, such as cusps and striations, completely depended on the fatigue crack growth rate, da/dN. In addition, a linear relationship between the fatigue striation space and the strain energy release rate range (ΔGs) and the hysteresis loop area was established. The Acoustic Emission (AE) method was also employed to characterize the damage features. The obtained results showed that higher AE energy indicates larger and rougher cusps and striation features.