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Progressive interlaminar failure analysis in composite missile structures

Bartan Kumbasar, Büşra
Interlaminar damage in composite structures is very crucial because it may cause splitting of the layers and lead to progressive failure of the whole structure. Delamination initiation and progression must be predicted accurately to aid the design of composites structures. Objective of the thesis is to investigate the interlaminar progressive failure behavior of the composite wing of a missile manufactured by twill composite by finite element analysis and tests. For this purpose, before the analyses and tests of the missile wing are performed, a simpler structure is modelled and tested to investigate the delamination behavior in the twill composite. In this study, simpler structure is selected as the open-hole plate. To initiate delamination, a thin film is inserted in a known location the composite plate in order to provoke delamination and examine the delamination progression behavior at different load levels. After the prediction of delamination initiation and propagation behavior by finite element analysis, open hole tensile test specimens are manufactured by the same twill composite which is used in the missile. Intact (OHT) and delaminated (DOHT) open hole tensile specimens are tested in tensile loading and comparisons are made with the experimental results. The load - displacement curve and load-strain curves obtained for the OHT specimens and DOHT specimens by the finite element analysis and the tests showed relatively good agreement. It is also shown that the increment of delamination areas measured for the DOHT specimens by the C-Scan differed from the finite element solution by %17. For the composite missile wings, similar analysis and test method is followed as the open-hole specimens but in bending load condition. It is shown that the increment of delamination areas measured for DWs by the C-Scan differed from the finite element solution by %7.3. The preliminary analysis performed on a real structure such as a composite missile wing showed that with the cohesive zone modeling, the progression of delamination can be predicted fairly accurately.