共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
采用两种形状(纺锤形、矩形)的拉伸试样对热压单向M40JB-Cf/SiC和T800-Cf/SiC复合材料进行了高温拉伸强度测试,得到了Cf/SiC复合材料的拉伸强度,并对纺锤形试样断裂应变的表达式进行修正,得出了复合材料的弹性模量。M40JB-Cf/SiC复合材料1300℃的拉伸强度及模量分别为374 MPa和134 GPa, 1450 ℃的拉伸强度及模量为338 MPa和116 GPa,T800-Cf/SiC复合材料1300 ℃拉伸强度和模量为392 MPa 和115 GPa。测试结果与试样的断裂方式密切相关,在有效部位断裂的测试结果大于在非有效区断裂的测试结果。M40JB-Cf/SiC复合材料的拉伸断裂应力-应变曲线表现出塑性变形的非线弹性破坏特征,而T800-Cf/SiC主要表现为线弹性特征。 相似文献
3.
E. R. de los Rios C. A. Rodopoulos J. R. Yates 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(9):1093-1105
Abstract— An investigation on the fatigue crack growth (FCG) and fatigue failure in metal matrix composites (MMCs) has been conducted using a model based on micromechanical elasto-plastic fracture mechanics (EPFM) principles. To evaluate the model, comparisons between experimental and predicted fatigue life have been made for two silicon carbide strengthened (SCS)-6/Ti-based MMCs. Conditions for crack arrest and crack instability have also been considered in order to define the fatigue damage limits. Crack arrest occurs from the added effects of fibre bridging and the constraint provided by the fibre on matrix microplasticity, while crack instability is achieved when the fibre constraint effect is minimum and the fatigue resistance of the material is reduced due to the accumulation of fatigue damage. Comparisons of the predicted fatigue damage limits with experimental results show good agreement which underlines the usefulness of a microstructural fracture mechanics model. 相似文献
4.
5.
6.
The fatigue crack growth response of Ti-based metal–matrix composites (MMCs) under single overloads was investigated. Extensive debonding and failure of bridging fibres were confirmed to be the major controlling mechanisms accelerating crack growth after peak overloads. Numerical predictions show that the fatigue damage severity is increased when the overload is applied at shorter crack lengths. Finally, extensive debonding and failure of bridging fibres was corroborated with a fatigue damage map to provide design guidelines. 相似文献
7.
E. R. de los Rios C. A. Rodopoulos J. R. Yates 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(5):539-550
A model based on micro-mechanical concepts has been developed for predicting fatigue crack growth in titanium alloy matrix composites. In terms of the model, the crack system is composed of three zones: the crack, the plastic zone and the fibre. Crack tip plasticity is constrained by the fibres and remains so until certain conditions are met. The condition for crack propagation is that fibre constraint is overcome when the stress at the location of the fibre ahead of the crack tip attains a critical level required for debonding. Crack tip plasticity then increases and the crack is able to propagate round the fibre. The debonding stress is calculated using the shear lag model from values of interfacial shear strength and embedded fibre length published in the literature. If the fibres in the crack wake remain unbroken, friction stresses on the crack flanks are generated, as a result of the matrix sliding along the fibres. The friction stresses (known as the bridging effect) shield the crack tip from the remote stress, reducing the crack growth relative to that of the matrix alone. The bridging stress is calculated by adding together the friction stresses, at each fibre row bridging the crack, which are assumed to be a function of crack opening displacement and sliding distance at each row. The friction stresses at each fibre row will increase as the crack propagates further until a critical level for fibre failure is reached. Fibre failure is modelled through Weibull statistics and published experimental results. Fibre failure will reduce the bridging effect and increase the crack propagation rate. Calculated fatigue lives and crack propagation rates are compared with experimental results for three different materials (32% SCS6/Ti-15-3, 32% and 38% SCS6/Ti-6-4) subjected to mode I fatigue loading. The good agreement shown by these comparisons demonstrates the applicability of the model to predict the fatigue damage in Ti-based MMCs. 相似文献
8.
将活性填料Al应用到吉林碳纤维(JC)和M40JB纤维增强先驱体转化SiC陶瓷基复合材料的制备中。研究表明,经过7个周期的致密化处理,当复合材料素坯中不含活性填料时,JC增强复合材料比M40JB增强复合材料有更高的弯曲强度,因此,JC纤维更适合用作先驱体转化陶瓷基复合材料的增强纤维;当复合材料素坯中含有活性填料Al时,由于Al与碳纤维发生碳化反应,使纤维受损,在纤维与基体之间形成不良的界面结合,导致复合材料的强度发生退化。图象分析表明,M40JB与Al的反应层厚度约为0.94μm。为了防止碳纤维与Al发生反应,应对碳纤维进行适当的表面处理。 相似文献
9.
自生TiC增强钛基复合材料的微观组织 总被引:6,自引:0,他引:6
采用反应自生法制备了TiC颗粒增强钛合金基复合材料,研究了复合材料的相组成和微观组织。在Ti-6Al-2C合金中存在Ti和TiC两种相。TiC权树枝状初生Tic和短棒状共晶TiC两种开头存在,其中共晶TiC主要存在于晶界,特别是三角晶界处。TiC晶格常数的计算结果表明TiC的衍射峰存在一定的偏移,主要是由于存在于TiC中的C空位引起晶格畸变。随着Al含量的增加,初生TiC由发达粗大的树枝晶变为不发达的树枝晶,当Al含量为35%时变为短棒状和薄片状的TiC。基体组织也相应地由单一的Ti基体变为Ti和Ti3Al的两相基体以及Ti3Al和TiAl两相基体。根据相图分析了组织变化的主要原因。 相似文献
10.
利用钛与碳化硼及石墨之间的自蔓延高温合成反应经普通的熔铸工艺原位合成制备了不同摩尔比值TiB和TiC增强的钛基复合材料。测定了原位合成钛基复合材料的高温力学性能。结果表明:由于增强体的原位合成,复合材料的高温拉伸性能与基体合金比较有了明显的提高。高温拉伸断裂与温度有关,温度较低时,增强体断裂是材料失效的主要原因;而随着温度的提高,增强体与基体合金界面脱粘成为材料失效的主要原因。高温拉伸时裂纹容易在短纤维状增强体TiB的端面处形核与长大从而使增强体与基体合金脱粘导致材料失效,因此加入石墨形成更多的TiC粒子有利于提高复合材料的高温力学性能。 相似文献
11.
将活性填料Al应用到吉林碳纤维(JC)和M40JB纤维增强先驱体转化SiC陶瓷基复合材料的制备中。研究表明,经过7个周期的致密化处理,当复合材料素坯中不含活性填料时,JC增强复合材料比M40JB增强复合材料有更高的弯曲强度,因此,JC纤维更适合用作先驱体转化陶瓷基复合材料的增强纤维;当复合材料素坯中含有活性填料Al时,由于Al与碳纤维发生碳化反应,使纤维受损,在纤维与基体之间形成不良的界面结合,导致复合材料的强度发生退化。图象分析表明,M40JB与Al的反应层厚度约为0.94 μm。为了防止碳纤维与Al发生反应,应对碳纤维进行适当的表面处理。 相似文献
12.
13.
采用单边缺口梁(SENB) 法、扫描电镜和电子理论, 研究了碳化钨(WC) 增强钢基复合材料经960~1040 ℃奥氏体化及淬火、回火共12 种状态的断裂行为和断口特征。实验结果表明, 该材料在具有高强度(σbb~2200 MPa,σbc~3000 MPa) 高硬度( HRC 62~68) 的同时, 还具有较高的SENB 断裂韧性(~30 MPa ·m1/2 ), 断口形貌主要特征为WC 解理、基体准解理及分散韧窝和韧窝带。研究发现, 高体积分数(~40 %) 的硬质相对材料的断裂韧性和断裂行为起决定性作用, 基体内存在的具有高共价键强的含碳结构单元和具有较多晶格电子的α-Fe (Ni) 结构单元共同作用, 既给予硬质相以强韧支持, 又产生断裂时的微观延性。 相似文献
14.
15.
在先驱体转化陶瓷基复合材料的制备中,坯体在裂解前后的体积发生变化。引入体系体积收缩率参数,对单一先驱体转化纤维增强陶瓷基复合材料致密化模型进行了修正。同时,分别对含惰性填料和/或活性填料的先驱体浆料浸渍-裂解纤维增强陶瓷基复合材料致密化进行了模型分析。从理论上揭示了复合材料的浸渍-裂解周期与材料的理论密度和理论孔隙率之间的关系。当先驱体浆料中含有活性填料时,复合材料的理论密度和理论孔隙率与活性填料的反应陶瓷产率、反应密度比、体积收缩率有密切的数学关系。在先驱体中引入活性填料比引入惰性填料能更为有效地提高材料的密度,降低材料的孔隙率。 相似文献
16.
SiCw/Al复合材料中SiCw的空间取向函数 总被引:3,自引:2,他引:1
通过理论分析,建立了SiCw/Al复合材料中SiCw的平面取向函数与空间取向函数的关系,研究了压铸态及挤压iCw/Al复合材料中SSicw的平面间取向函数。结果表明,复合材料中SiCw平面取向函数与空间取向函数存在明显差咖;其中空间取向函数代表复合材料中SiCw的实际取向分布状态,与复合材料中的各工异相符合。 相似文献
17.
基体改性碳/碳复合材料抗氧化影响规律探析 总被引:8,自引:1,他引:7
碳/碳复合材料(以下简称C/C)在空气中400℃以上显着氧化,目前所采用的防氧化涂层不能很好地解决涂层与基体间热膨胀所带来的裂纹问题,我们认为,同时着重于C/C本身改性及其涂层的抗氧化性提高,是大大改善其抗氧化性能的有效途径.本论文就是基于这一出发,点,在C/C基体中加ZrO2、SiO2、SiC等玻璃陶瓷粉,并且将数学工具引入实验,得到了基体添加剂对C/C抗氧化性的影响规律,实验结果表明,SiO2、B4C等玻璃陶瓷粉显着改善C/C的抗氧化性能,大大降低氧化烧蚀率. 相似文献
18.
19.