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

9423668杜塔本研究采用分析和实验相结合的方法，对单向增强、连续纤维、金属基复合材料(MMC)的蠕变机理进行了全面的研究。这项工作的独到之处有三个方面：(1)它寻求建立一个模型，明确地解释应变历史、界面滑动和随时间变化的基质蠕变；(2)它通过提出对基质、界面和纤维对整体蠕变响应的作用的实验量化来寻求力学洞察力，而不是预测能力；(3)它是迄今为止以瞬时变形机制图的形式总结连续纤维MMC中蠕变机制的应力-温度-时间依赖关系的唯一尝试，这对于预测在广泛的应力和温度条件下复合材料的应变响应和主要变形机制是有价值的。该实验方案包括一种在复合材料蠕变试验期间实时监测损伤机制的新方法。连续纤维复合材料的蠕变响应是复杂的，因为载荷从基体逐渐传递到纤维上，导致了暂态行为，这给力学研究带来了困难。这是复杂的纤维-基质界面滑动，内部残余应力与施加的应力的相互作用，以及基质变形机制随着应力条件的变化而变化。因此，连续纤维增强金属基复合材料(MMC)的蠕变现象还没有出现。%该项目有望对连续纤维MMC的蠕变机制，特别是基质和界面变形的作用提供实质性的基础性见解。

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.