侯军涛
,
乔生儒
,
张程煜
,
张跃冰
新型炭材料
doi:10.1016/S1872-5805(08)60046-3
3D-C/SiC复合材料试样在空气介质中600℃、900℃和1300℃热曝露不同时间后,采用三点弯曲法测试了以室温弯曲弹性模量表征的损伤变化规律,并进行了SEM和EDS分析.结果表明:3D-C/SiC在热曝露15 h后,损伤变化可分为急剧上升(阶段Ⅰ)和平稳上升(阶段Ⅱ)两个阶段.阶段Ⅰ归因于炭纤维和炭层界面在空气中的直接氧化,阶段Ⅱ由复合材料内部氧的扩散所致.在复合材料制备过程的冷却阶段,因基体和炭纤维热膨胀系数不同所产生的基体微裂纹提供了氧化反应的表面与氧扩散的途径.在同一热曝露时间下,损伤随温度的上升而减少的原由可能是由于高温下裂纹收缩导致氧化表面减少,并降低氧向复合材料内扩散所致.
关键词:
3D-C/SiC
,
热曝露
,
损伤
,
弯曲性能
乔生儒
,
杨忠学
,
韩栋
,
李玫
材料工程
doi:10.3969/j.issn.1001-4381.2004.04.009
对3D-C/SiC复合材料进行拉伸蠕变试验,蠕变进行一段时间后,用扫描电子显微镜(SEM)观察试样表面的变化,同时测量试样的共振频率.结果表明,3D-C/SiC除通常CMC所产生的蠕变损伤外,纤维束滑动,纤维束之间的夹角变化,孔隙变形,部分孔隙表面空间位置改变,孔隙表面产生基体微裂纹,损伤在纤维束交叉处更为集中,这些可作为3D-C/SiC蠕变变形的独特机理.电阻和模量的相对变化与蠕变曲线相似,因此电阻和模量都可表征C/SiC材料的蠕变损伤,作为损伤变量.该材料的蠕变属于损伤引起.
关键词:
蠕变损伤机理
,
3D-C/SiC
,
纤维束交叉处
,
模量
,
损伤表征
罗国清
,
乔生儒
材料工程
doi:10.3969/j.issn.1001-4381.2003.10.003
研究了在室温、1100和1500℃夹头位移速率分别为0.008,0.06和5.82 mm/min对CVI工艺制备的3D-C/SiC拉伸性能的影响.拉伸中用钨-铼热电偶测温,真空度为10-3Pa,LVDT测量变形.结果表明,室温条件下材料的断裂应力随夹头位移速率的增大而增加;1500℃断裂应力随夹头位移速率的增大而减小;1100℃条件下断裂应力基本不随变形速率而改变.随着夹头位移速率的提高,断裂应变减小,初始弹性模量增加.分析了可能造成以上现象的因素.
关键词:
夹头位移速率
,
3D-C/SiC
,
拉伸性能
,
高温
任伟华
,
乔生儒
,
敖强
材料工程
doi:10.3969/j.issn.1001-4381.2003.12.007
用3D-C/SiC和重结晶SiC陶瓷材料在光辐射热震试验机上进行了两种温度落差(AT=600 ℃,800 ℃)和不同应力的热震试验.3D-C/SiC用弹性模量和电阻表征的热震损伤曲线有相似的规律,即都大致由三阶段构成,首先是损伤急剧增加阶段,紧接着是损伤缓慢增加阶段,最后为损伤短暂的急剧增加阶段.个别电阻表征的热震损伤曲线仅在初始阶段损伤有下降现象.3D-C/SiC复合材料的抗热震性能明显优于重结晶SiC陶瓷材料;三种界面层的3D-C/SiC中,以热解碳沉积时间为20h获得的界面层复合材料热震寿命最长.
关键词:
热震
,
3D-C/SiC
,
重结晶SiC
,
损伤
,
弹性模量
D.Han
,
S.R.Qiao
,
M.Li
,
J.T.Hou
,
X.J.Wu
金属学报(英文版)
The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.
关键词:
2D-C/SiC
,
null
,
null
G.C.Ji
金属学报(英文版)
Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterized by evaluation the load/qoad point displacement curves tested by three points bend experiment with single notch beam at 1300℃. The cracks length was determined by compliance calibration curves. It is shown by experimental results that the compliance of 3D-C/SiC composites changes with the cracks can be described by third order polynomial. The variation of crack advancing resistance with non-dimensional equivalent crack length presents a convex curve. The crack advancing resistance increases firstly and then decreases with the non-dimensional equivalent crack length, finally is in comparatively low level. The maximum values of crack advancing resistance are 269.73k J/m^2 for nondimensional equivalent crack length of 0.318 and original notch length of 0.35mm, and 138.65kJ/m^2 for non-dimensional equivalent crack length of 0.381 and original notch length of 2.06mm, respectively.
关键词:
fracture resistance
,
null
,
null
