An Analytical and Experimental Study of Longitudinal Creep in Countinous Fiber Composites

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9423668 Dutta This research is a comprehensive investigation of creep mechanisms in unidirectionally reinforced, continuous fiber, metal-matrix composites (MMCs), combining both analytical and experimental approaches. The work is unique in three respects: (1) it seeks to develop a model, which explicitly accounts for strain history, interfacial sliding, and time-dependent changes in matrix creep; (2) it seeks mechanistic insight, rather than predictive ability, by proposing experimental quantification of the roles of the matrix, interface and fiber on the overall creep response; (3) it constitutes the only attempt to date at summarizing the stress-temperature-time dependence of creep mechanisms in continuous fiber MMCs in the form of transient deformation mechanism maps, which are valuable in predicting the strain response and dominant deformation mechanisms in composites over a wide range of stress and temperature conditions. The experimental program includes a novel approach to monitor damage mechanisms in real time during creep testing of composites. The creep response of continuous fiber composites is complex because of progressive transfer of load from the matrix to the fibers, resulting in transient behavior which makes mechanistic studies difficult. This is complicated by fiber-matrix interfacial sliding, interaction of internal residual stresses with the applied stresses, and changes in the matrix deformation mechanism with evolving stress conditions. Accordingly, a clear phenomenological picture of creep in continuous fiber reinforced metal-matrix composites (MMC) has not emerged. %%% This project is expected to yield substantial fundamental insight on creep mechanisms in continuous fiber MMCs, particularly with respect to the roles of matrix and interface deformation.