ECCOMAS 2024

Investigation of Interlaminar Fatigue Damage Behaviour of Composite Structures via Two-Way Coupling Global-Local Analysis

  • Değerliyurt, Boray (Turkish Aerospace)
  • Şahin, Melin (METU)

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Delamination and debonding stand out as crucial failure modes in composite helicopter rotor components, demanding accurate estimation of their growth and extent. A rapid and robust approach for analyzing progressive fatigue delamination is essential to assess the propagation of interlaminar flaws. Existing literature primarily confines progressive failure investigations to coupon scale due to substantial computation times and convergence challenges. The commonly observed strategy to tackle these issues involves the utilization of the global-local method. While global-local methods are prevalent in progressive damage computations, they are typically limited to static analyses; and the literature lacks global-local methods specifically designed for progressive fatigue damage modeling. The simplest form of the global-local method is sub-modeling where the displacement field derived from the intact global model is applied to the boundary of the local model once. In cases of substantial damage resulting in significant global structural stiffness changes, relying on the unchanged displacement field of the intact global model may mislead and result in inaccurate solutions. Therefore, according to the damage state of the local model, the global model should be updated accordingly via a two-way coupled method. Consequently, this study introduces a novel procedure for conducting extensive fatigue delamination analyses with a two-way coupling global-local method. The approach encompasses fatigue progressive inter-laminar damage modeling with cohesive elements. In this method, the displacement field derived from the global model is applied to the local model; and subsequently, the global model is updated iteratively based on internal nodal reactions of cohesive elements extracted from the local model. The study presents the results of analysis of Double Cantilever Beam (DCB) model employing this method, comparing them with regular methodologies and experimental findings to verify the proposed approach. The method gives consistent results with regular analyses and experimental findings. In 3D models with finer local mesh, the current method has a significant computational advantage over regular analyses.