D and 3D finite element analyses of dynamic delamination in curved CFRP laminates

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2019
Ata, Tamer Tahir
Most of the aerospace structures such as spars and ribs contain curved regions in which presence of curved region induces significant tensile stresses in the radial direction in these complex parts. Since composite materials inherently have low mechanical properties in the transverse direction, transverse tensile stresses developed in curved region cause delamination which reduces load carrying capacity of the component and even leads to collapse of the part. In this study, progressive interlaminar damage in curved CFRP composite laminates with two different ply architectures (unidirectional and fabric) are investigated by using ABAQUS/Explicit in conjunction with cohesive zone elements. The simulations are based on the experiments conducted by Tasdemir [ 1 ]. 2D and 3D finite element analyses of the considered two specimens (UD and fabric) are performed under moment/axial combined loading. In both 2D and 3D analyses, delamination is found to induce at the center of the curved region which is exactly the maximum radial stress location. 2D and 3D finite element analyses of dynamic delamination in curved composite laminates revealed that the crack propagation speeds inside the laminate varies as edge crack travels faster than center crack. For UD laminate, delamination initiates at the center of the width of the laminate and as the crack passes to arm region it travels in Mode-II dominancy at intersonic speeds. For fabric laminate, delamination initiates at the center of the width of the laminate. It is interesting to observe the delamination onset at center of the width instead of free-edge where the material mismatch exists between different layer orientations. 3D analysis is found to capture effects that are not seen in the 2D analysis. The analysis agrees well with the experimental results in terms of damage initiation location through the thickness direction and load-displacement trend. To the author’s knowledge, this is the first study to model the dynamic delamination in curved CFRP laminates using 3D simulations.

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Citation Formats
T. T. Ata, “D and 3D finite element analyses of dynamic delamination in curved CFRP laminates,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2019.