Modeling of mixed-mode delamination in composite t-joints

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Havacılık ve Uzay Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: HASAN GÜLAŞIK

Danışman: DEMİRKAN ÇÖKER

Özet:

Stiffened panel, consisting of skin and stiffeners, is the main design option for aerospace structures. When manufactured with laminated composite materials, they provide high strength/stiffness to weight ratio, resulting in high performance and less fuel consumption. T-joint is one of the typical configurations for composite stiffened panels which consist of a skin panel and stiffeners co-bonded or co-cured together with a filler material between them. T-joints are prone to delaminations between skin/stiffener plies and debonds between skin-stiffener-filler interfaces. In this study, delamination/debond behavior of a co-bonded composite T-joint is investigated with 2D finite element method. A commercial FEA software, Abaqus with zero-thickness cohesive elements with bilinear cohesive law is used to simulate delamination/debond at all ply interfaces and bonding lines in the structure. Numerical results for the T-joints show that, delamination/debond initiation and propagation scenarios are different for 0°, 45° and 90° pull loads which simulate different loading conditions in aerospace structures. Different failure initiation mechanisms of the T-joints observed in the literature are captured in a parametric study for 0° pull load with geometry and material property changes. Failure initiation and propagation behaviors, load displacement curves, initial and max failure loads and stress fields are affected by the property changes. Generally, mixed-mode behavior is observed in the failure initiation and propagation stages. Additionally, in the numerical studies of the DCB, ENF and MMB delamination tests, Abaqus CZM is validated with the analytical solutions and the numerical and experimental data from the literature.