塑性相结合刚玉复合材料的力学性能

在刚玉－碳化硅耐火材料中添加硅粉,利用硅粉所具有的金属塑性特征,使得制品具有了塑性成型的性质,而且提高了制品的致密化程度和断裂韧性,并达到了坯体增韧的效果。     

多轴向经编/缝合织物增强复合材料冲击后压缩强度研究

本文采用冲击后压缩强度试验对多轴向经编／缝合复合材料的损伤容限进行了研究。结果表明：与层合板复合材料相比,多轴向经编／缝合复合材料的冲击后压缩强度提高了１００％以上,说明缝合对提高材料的抗损伤容限有较大的贡献。最后探讨了多轴向经编／缝合复合材料具有优越的综合性能及广阔的应用前景。     

不同缝合方式对缝合复合材料力学性能的影响研究

缝合技术作为整体成型的制造技术,能有效增强复合材料的层间强度和抗冲击损伤性能。在缝合技术中有不同的缝合方式,目前常用的缝合方式有锁式缝合、链式缝合和临缝三种。不同的缝合方式对复合材料的层间剪切性能、压缩性能、拉伸性能和弯曲性能会产生不同的影响。主要研究了在三种不同的缝合方式下,复合材料的压缩性能、拉伸性能和弯曲性能的变化。     

缝合技术在复合材料上的应用及研究进展

从缝合工艺特点及缝合参数等方面简述缝合技术,综述了近年来缝合复合材料的主要微观力学模型及缝合对复合材料力学性能的影响,介绍了缝合复合材料力学性能的研究进展,并对缝合复合材料的发展趋势进行了展望。     

碳布复合材料力学性能研究

测试了两种不同经纬编织密度和不同含胶量的碳布／环氧复合材料的基本力学性能，对碳纤维复丝及碳布在复合材料中的强度利用率作了比较与分析。结果表明：适当增大含胶量有利于改善复合材料的力学性能；经纬编织密度对复合材料力学性能的影响同样不可忽视。     

缝合工艺在碳/碳复合材料的应用

研究了不同缝合间距和不同碳布对碳/碳缝合复合材料力学性能的影响.结果 表明:在相同缝合间距下,缝合预制体的单元层厚度越薄,其碳/碳复合材料的综合性能越优异,且相比单元层性能,单元层厚度对其碳/碳复合材料的性能影响更显著;随着缝合间距变小,碳/碳复合材料拉伸强度整体呈现下降趋势,且降低幅度均增大,弯曲强度和层间强度呈现增加趋势,且增加幅度均增大.     

基于损伤容限设计的金属材料力学性能评价方法

常规方法评价金属材料力学性能时,力学响应测量值偏差较大,针对这一问题,提出基于损伤容限设计的金属材料力学性能评价方法.利用动态冲击压痕装置,动态冲击金属材料样品,造成材料损伤,统计样品出现裂纹时的施加载荷和压痕数据,计算损伤容限下的力学响应,包括弹性模量、硬度、强度,计算值越大,表明金属材料力学性能的评价等级就越高.实...     

针织复合材料的力学性能

本文介绍了针织复合材料预型件的制造工艺：研究其面内和面外力学性能：并与机织复合材料进行了比较。     

缝合增强泡沫夹芯结构复合材料力学性能研究

采用机械缝合设备连续制备了"X"型构型缝合增强泡沫夹芯结构预成型体,并采用真空导入模塑工艺(VIMP)整体成型了缝合增强泡沫夹芯结构复合材料。实验研究了面板纤维布层数、面板纤维布穿透缝合层数、缝合角度、缝合针距及纱线股数对缝合增强泡沫夹芯结构复合材料弯曲性能和平压性能的影响规律。实验结果表明:与未缝合结构相比,缝合结构在质量未明显增加的情况下,弯曲性能和压缩性能得到了显著提高,其弯曲刚度最大提高了4.66倍,破坏载荷最大提高了13.8倍;压缩强度和压缩模量最大分别提高了26.2倍和15.2倍。     

Notch Sensitivity of Ceramic Composites with Rising Fracture Resistance

A theoretical framework is developed for the notched strength of ceramic composites that exhibit rising fracture resistance. It is based on established concepts of crack stability under stress-controlled loadings. On using a linear representation of the resistance curve (expressed in terms of an energy release rate), straightforward analytical solutions are obtained for the strength as well the amount of stable crack growth preceding fracture and the associated fracture resistance. Calculations are performed for several test configurations commonly used for material characterization, including single- and double-edge-notched tension, center-notched tension, and single-edge-notched bending. The results reveal salient trends in strength with notch length and specimen geometry. An assessment of the theory is made through comparison with experimental measurements on an all-oxide fiber composite. Transitions in the degree of notch sensitivity with notch length are identified and explored. The utility of the theoretical results both for rationalizing the trends in measured notched strength and for guiding experimental studies of notch sensitivity is demonstrated.     

微波烧结对ZTA陶瓷力学性能的影响

本文选用微波烧结新工艺,对ZTA陶瓷力学性能进行了研究,获得了较传统烧结工艺优良的陶瓷抗奇强度和断裂韧性。新工艺可以显著降低ZTA陶瓷的致密化温度,同时改善其显微结构。     

三维缝合复合材料微观力学模型研究进展

三维缝合复合材料由于复杂的微观结构，其力学性能与层合板的力学性能有着本质的区别。许多研究者通过理论分析模型的建立来模拟其真实的内部结构，以达到预测其力学性能的目的。本文综述了近年来提出的一些主要的微观理论分析模型，分析了其存在的优缺点，并以此指导力学工作者合理地选择计算模型，使之能对三维缝合复合材料进行较为精确的力学性能预报。     

Enhanced Mechanical Properties of Alumina by Dispersed Titanium Diboride Particulate Inclusions

The mechanical properties of composite ceramics composed of 0 to 20 vol% of titanium diboride particles dispersed in an α-alumina matrix were investigated. The alumina–titanium diboride composite powder was hot-pressed at 1470°C for 20 min to achieve over 98.8% of the theoretical composite density. The strength and fracture toughness of the twophase, hot-pressed composite were both significantly improved compared to the single-phase alumina. Results from different methods of measuring the stress intensity factor, ( K _{I c} ) are compared and discussed.     

Mechanical Properties of Bismaleimides Modified Polysulfone Epoxy Matrices

Epoxy resin has been chemically modified using 4, 8, and 12% of bisphenol-A based polysulphone along with three types of bismaleimides, namely [N, N′-bismaleimido-4,4′-diphenylmethane (BMI-1), 1,3-bis (maleimido) benzene (BMI-2) and 1,1′-bis (4-maleimidophenyl) cyclohexane (BMI-3)]. The epoxy hybrid matrices developed, in the form of castings, were used to characterize their mechanical properties like tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength, hardness, and dynamic mechanical analysis as per ASTM standards. Data obtained from mechanical studies indicate that the introduction of hydroxyl terminated polysulfone into epoxy resin enhanced the value of impact strength to the extent of 48% due to the formation of flexible graft structures. Similarly, the incorporation of bismaleimides into epoxy resin also improved both tensile and flexural behavior of epoxy resin. Further, the introduction of combination of both polysulfone and bismaleimides into epoxy resin improved the mechanical properties according to their percentage content. Among the bismaleimides-modified polysulfone epoxy matrices, the epoxy matrix modified with 8% polysulfone and 8% BMI-2 exhibited better mechanical properties than other modified epoxy matrices.     

Mechanical Properties of β-Si3N4-Whisker/Si3N4-Matrix Composites

Composites containing 30 vol%β-Si₃N₄ whiskers in a Si₃N₄ matrix were fabricated by hot-pressing. The composites exhibited fracture toughness values between 7.6 and 8.6 MPa · m^1/2, compared to 4.0 MPa · m^1/2 for unreinforced polycrystalline Si₃N₄. The improvements in fracture toughness were attributed to crack wake effects, i.e., whisker bridging and pullout mechanisms.     

纳米SiC增韧Al_2O_3陶瓷复合材料的制备、表征及力学性能研究

以SiC和Si微米粉为添加剂,采用无压烧结工艺制备了纳米SiC增韧的Al2O3陶瓷复合材料,探讨了SiC含量、烧结气氛和烧结温度对复合材料的烧成收缩率、微观形貌、抗弯强度、维氏硬度及断裂韧性的影响。结果显示：SiC的添加使复合材料的烧成收缩率下降,惰性气氛下复合材料的收缩率要大于氧化气氛和还原气氛时的收缩率。在氧化性气氛下烧结时,当SiC添加量为4%时,复合陶瓷的体积密度为3.80 g·cm^-3,抗弯强度、断裂韧性及维氏硬度均达到最大值,分别为480 MPa、5.12 MPa·m1/2、16.2 GPa。添加SiC后所得复合材料的基体颗粒为椭圆状,粒径为2μm左右,颗粒与颗粒之间结合紧密,颗粒形状的改变可能是因为烧结机理发生变化所致。纳米SiC颗粒位于晶界处,形成了由Al2O3-SiC-Al2O3搭桥联结的晶界,提高了晶界强度,导致裂纹只能在晶内传播。     

Mechanical Properties of Monoclinic Zirconia

Fracture toughness and fracture strength data are presented for the first time for monoclinic zirconia. An undoped nanocrystalline zirconia powder was sintered at 1100°C and yielded a theoretical density of more than 90% with a grain size of about 150 nm. The surface crack in flexure (SCF) technique was deemed most suitable for nanocrystalline materials. Measurements of Young's modulus and the determination of the fracture origin are also provided.