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

• Published in: Engineering fracture mechanics Vol. 241; p. 107408
• Main Authors: Mohammadi, Reza, Najafabadi, Mehdi Ahmadi, Saghafi, Hamed, Saeedifar, Milad, Zarouchas, Dimitrios
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.01.2021; Elsevier BV
• Subjects: Acoustic emission; Acoustic microscopy; Carbon-epoxy composites; Carbon/epoxy laminate; Crack propagation; Cusps; Cyclic loads; Damage detection; Emission analysis; Fatigue damages features; Fatigue failure; Fracture mechanics; Fracture surfaces; Heat treating; Hysteresis loops; Laminates; Mode-II loading; SEM analysis; Strain energy release rate; Striations; Fatigue damages features; SEM analysis; Acoustic emission; Carbon/epoxy laminate; Mode-II loading
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2020.107408

•The Mode II fatigue damage was studied at some crack growth rates using SEM and AE.•Fiber imprints, cusps, and striations, as damage features were identified.•It was found that more damage features indicate more dissipated energy.•The mode II fatigue damage features showed a dependency on the da/dN.•There is a relationship between striation space, ΔGs, fatigue hysteresis loop area.•Larger and rougher cusps and striation features emit higher acoustic energy. 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.