Strain-rate-dependent failure criteria for composites |
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Authors: | I.M. Daniel B.T. WernerJ.S. Fenner |
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Affiliation: | Robert McCormick School of Engineering and Applied Science, Northwestern University, 2137 Tech Drive, Evanston, IL 60208, USA |
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Abstract: | The objective of this study was to characterize the quasi-static and dynamic behavior of composite materials and develop/expand failure theories to describe static and dynamic failure under multi-axial states of stress. A unidirectional carbon/epoxy material was investigated. Multi-axial experiments were conducted at three strain rates, quasi-static, intermediate and high, 10−4, 1 and 180-400 s−1, respectively, using off-axis specimens to produce stress states combining transverse normal and in-plane shear stresses. A Hopkinson bar apparatus and off-axis specimens loaded in this system were used for multi-axial characterization of the material at high strain rates. Stress-strain curves were obtained at the three strain rates mentioned. The measured strengths were evaluated based on classical failure criteria, (maximum stress, maximum strain, Tsai-Hill, Tsai-Wu, and failure mode based and partially interactive criteria (Hashin-Rotem, Sun, and Daniel). The latter (NU theory) is primarily applicable to interfiber/interlaminar failure for stress states including transverse normal and in-plane shear stresses. The NU theory was expressed in terms of three subcriteria and presented as a single normalized (master) failure envelope including strain rate effects. The NU theory was shown to be in excellent agreement with experimental results. |
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Keywords: | A. Polymer-matrix composites (PMCs) B. Mechanical properties B. Strain rate effects C. Failure criterion D. Dynamic testing |
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