Numerical modeling of failure in composite L-beam and T-joint structures

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2022-12-02

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Temiz, Pakize

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Laminated curved-shape composite structures which are used as stiffening components in aerospace, wind, automotive and marine industries are subjected to high radial and tangential stresses. For the scope of this thesis, different modelling strategies are investigated to simulate interlaminar and intralaminar failure in composite L-beam and T-joint structures using commercial finite element (FE) code ABAQUS/Standard 2020. In the first part, [030] and [03/903/03/903/03]s laminated L-beams are evaluated using implicit finite element analysis. 3D and 3D-slice FE models are generated, and XFEM in conjunction with LaRC05 criteria and CZM in conjunction with QUADS initiation criteria and Benzeggagh-Kenane (BK) propagation criterion are used separately. The implicit FE results are validated in terms of load-displacement behavior, stress fields, and failure location with both explicit analysis results and experimental results for [030] laminates. For [03/903/03/903/03]s laminates, the results were compared to the experimental results in the literature. For cross-ply L-beam specimens, failure load is overestimated compared to the experiments in literature. Additional FE analyses are carried out with reduced strengths considering the observed defects and ply mismatch angle at the interface which results in comparable failure load with experiments. To the authors’ best knowledge, this is the first study implementing LaRC05 failure criteria to analysis of L-beam structures. In the second part, 2D implicit FE models with CZM is used to model T-joints under axial loading and compared with 3D implicit FE results in terms of the load-displacement curves, stress fields and failure locations to address the 3D effects. 3D model revealed that the debonding initiates at the middle-width of the filler/stringer interface and extends towards the free edges. Furthermore, 2D implicit FE models with CZM is used to model T-joints under oblique and transverse loadings and compared to axial loading. T-joint under 45° loading resulted in higher load bearing than the others due to opposing mechanisms of vertical and horizontal components of the loading. The results of this thesis contribute to the understanding of failure mechanisms of L-beam and T-joint structures.

Subject Keywords

Composite, Delamination, L-beam, T-joint, Matrix cracking

URI

https://hdl.handle.net/11511/101856

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

P. Temiz, “Numerical modeling of failure in composite L-beam and T-joint structures,” M.S. - Master of Science, Middle East Technical University, 2022.