STP1206

    The Effect of Mixed-Mode Loading on Delamination Fracture Toughness

    Published: Jan 1993


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    Abstract

    Interlaminar fracture (delamination) is the dominant failure mechanism in most advanced composite materials. The resistance of a material system to delamination failure is generally quantified in terms of the interlaminar fracture toughness, Gc. The recently developed Mixed-Mode Bending (MMB) test is unique in that it facilitates measurement of the fracture toughness Gc under any combination of mixed-mode loading from pure Mode I to pure Mode II. This makes it a very attractive technique for developing interlaminar fracture failure criteria. This paper reports on an application of the MMB test to fatigue loading for the generation of Gc versus-curves and identification of the threshold value, Gth. Fatigue results from unidirectional IM7/5260 graphite/bismaleimide and IM7/8320 graphite/thermoplastic specimens are presented for a GI/GII ratio of 0.25. Static test results are also presented for both materials with the mode mix varying from pure Mode I to pure Mode II. The static results indicate different mixed mode failure laws for the two materials. All tests were conducted using displacement controlled loading under room temperature, dry conditions.

    Keywords:

    composite materials, laminated composites, delamination, fatigue testing, interlaminar fracture toughness, mixed-mode strain energy release rate


    Author Information:

    Sriram, P
    Assistant professor, graduate student, and associate professor, Wichita State University, Wichita, KS

    Khourchid, Y
    Assistant professor, graduate student, and associate professor, Wichita State University, Wichita, KS

    Hooper, SJ
    Assistant professor, graduate student, and associate professor, Wichita State University, Wichita, KS


    Paper ID: STP12635S

    Committee/Subcommittee: D30.06

    DOI: 10.1520/STP12635S


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