Damage accumulation during high temperature fatigue of Ti/SiCf metal matrix composites under different stress amplitudes
Damage accumulation during high temperature fatigue of Ti/SiCf metal matrix composites under different stress amplitudes
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DOI：
10.1016/j.actamat.2021.116976
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发表时间：
2021-02
期刊：
影响因子：
9.4
通讯作者：
Ying Wang;Xu Xu-Xu;W. Zhao;Nan Li;S. McDonald;Yuan Chai;M. Atkinson;K. Dobson;Š. Michalik
中科院分区：
文献类型：
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作者：
Ying Wang;Xu Xu-Xu;W. Zhao;Nan Li;S. McDonald;Yuan Chai;M. Atkinson;K. Dobson;Š. Michalik
采用同步辐射X射线计算机层析(CT)和X射线衍射仪(X射线衍射仪)研究了TC17钛合金/单向碳化硅纤维复合材料在两种应力幅值下高温(350℃)高周疲劳(HCF)的损伤机制和载荷重分布。用CT绘制了疲劳裂纹和纤维断口的三维形貌图。在低应力幅值下，发生稳定增长，基质裂纹绕过桥联纤维，高度偏转50-100微米。在较高的应力幅值下，加载到峰值应力会导致纤维断裂，从而导致裂纹的快速扩展。在快速生长阶段，许多纤维断裂发生在基体裂纹面的上方/下方50-300微米，与稳定生长阶段相反，导致断口表面广泛的纤维拔出。用X射线衍射仪绘制了疲劳循环和裂纹快速扩展后裂纹附近纤维载荷、界面应力和纤维基质脱粘程度的变化图。纤维/基质界面滑移延伸到裂纹面两侧的600微米(在稳定增长区)或700微米(在快速增长区)。在加载循环过程中，界面剪应力方向相反，两种状态下的最大摩擦滑动应力都达到了~55 Mpa。根据以前的研究，高温下纤维强度的下降可能是导致纤维断裂和在较高应力幅值下快速裂纹扩展的原因。
The damage mechanisms and load redistribution taking place under high temperature (350 °C), high cycle fatigue (HCF) of TC17 titanium alloy/unidirectional SiC fibre composites have been investigatedin situusing synchrotron X-ray computed tomography (CT) and X-ray diffraction (XRD) under two stress amplitudes. The three-dimensional morphology of the fatigue crack and fibre fractures has been mapped by CT. At low stress amplitude, stable growth occurs with the matrix crack deflecting by 50-100 µm in height as it bypasses the bridging fibres. At higher stress amplitude, loading to the peak stress led to a burst of fibre fractures giving rise to rapid crack growth. Many of the fibre fractures occurred 50-300 µm above/below the matrix crack plane during rapid growth, contrary to that in the stable growth stage, leading to extensive fibre pull-out on the fracture surface. The changes in fibre loading, interfacial stress, and the extent of fibre-matrix debonding in the vicinity of the crack have been mapped over the fatigue cycle and after the rapid crack growth by XRD. The fibre/matrix interfacial sliding extends up to 600 µm (in the stable-growth zone) or 700 µm (in the rapid-growth zone) either side of the crack plane. The direction of interfacial shear stress reverses over the loading cycle, with the maximum frictional sliding stress reaching ~55 MPa in both regimes. In accordance with previous studies, it is possible that a degradation in fibre strength at elevated temperature is responsible for bursts of fibre fracture and rapid crack growth under higher stress amplitude.