Conventional finite element analysis (FEA) tools have been extensively developed over the last several decades and are now heavily employed for simulating 2D fatigue propagation in laminated carbon fibre reinforced polymer (CFRP) composites. Arguments were raised regarding their reliability in this context due to neglecting the stress strain redistribution at the crack tip which requires continuous remeshing. Alternatively, extended finite element modeling (XFEM) techniques were introduced to overcome this shortcoming with no need of meshing at the crack tip. The new technique adopted eitherapproaches of virtual crack closure technique (VCCT) based on linear elastic fracture mechanics (LEFM) concepts, or cohesive zone methods (CZM). However, its application in available commercial tools typically pertains to 2D quasi-static problems. In this work, we considered 3D damage propagation of multiple modes; delamination, matrix cracks and fibre breakage in CFRP samples subjected to constant amplitude fatigue loading. An assessment was performed on the reliability of Abaqus tool in addressing combined-mode 3D damage propagation caused by fatigue stress, and results from simulations were compared to experimental data. Fatigue behaviour was experimentally tracked using Skyscan 1173 micro computed tomography (microCT) scans of CFRP samples at different levels of fatigue lives. Virtual slices obtained throughout the thicknesses of the samples volumes were visually analyzed and further rendered and processed by applying a threshold method to define the 3D damaged areas and classify the damage modes. Finally, the stacked segmented volumes were meshed for importing to FEA modeling. Limitations of the available commercial FEA tool in addressing the problem are discussed, and the introduced testing procedure was proved to be reliable in providing the quantitative information necessary for analyzing fatigue behaviour and for potentially developing analytical models that may overcome the current limitations.

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Conference Composites and Advanced Materials Expo: Combined Strength. Unsurpassed Innovation., CAMX 2014
El Agamy, N. (Naglaa), Martin, C. (Camille), Sachdeva, T. (Taran), & Laliberte, J. (2014). Proposed procedure to simulate 3D multi-mode fatigue behaviour in laminated CFRP using micro-ct scans in Abaqus. Presented at the Composites and Advanced Materials Expo: Combined Strength. Unsurpassed Innovation., CAMX 2014.