Interface Toughness Measurements in Blade Stiffened Composite Skin Specimens

Masood, Nadeem and Viswamurthy , SR and Gaddikeri, KM (2014) Interface Toughness Measurements in Blade Stiffened Composite Skin Specimens. In: 18th NASAS (Eighteenth National Seminar on Aerospace Structures), 15-17 December 2014, VNIT Nagpur.

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Separation of skin and stringer is likely to be a failure mode in structures where there is considerable out-of-plane deformation. Such deformations are possible when a stiffened skin structure is loaded in compression/shear beyond buckling or in structures which contain a flaw/defect at the skin-stringer interface. Prediction of such a failure in numerical simulations requires parameters such as interface fracture toughness which have to be obtained through specimen tests. Since, interface toughness is generally mode dependent, this study deals with testing of blade stiffened composite skin specimens under pure Mode-I and Mode-II loading. Specimens are fabricated with Carbon/Epoxy unidirectional prepreg (IMA/M21) material using autoclave molding process. Mode-I & Mode-II interface fracture toughness tests are conducted on blade stiffened composite skin specimens. All specimens contain an initial disbond of known size at the interface between the skin and stringer flange. This disbond is created by placing a thin non-adhesive insert of appropriate size at the interface during layup. Test fixtures are also designed and fabricated. Tests are conducted in displacement control mode in a UTM. Disbond length at various loads is recorded. Compliance calibration method is used to determine the interface fracture toughness in both modes. The interface toughness of blade stiffened skin specimens are found to be different from interlaminar fracture toughness obtained from conventional double cantilever beam and end-notched flexure tests.

Item Type: Conference or Workshop Item (Paper)
Subjects: CHEMISTRY AND MATERIALS > Composite Materials
ENGINEERING > Structural Mechanics
Depositing User: Dr. Viswamurthy S R
Date Deposited: 07 Jan 2015 10:04
Last Modified: 07 Jan 2015 10:04

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