常温冲孔性优良的CEM-1覆铜板的研制

本文介绍了一种CEM-1覆铜板的制作方法,采用这种方法制作的覆铜板具有优良的常温冲孔性和良好的性价 比。     

CEM-1覆铜板的研制

本文介绍了CEM-1覆铜板用环氧树脂的增韧改性、CEM-1覆铜板的制作及其性能。     

Toughening Mechanisms in Cemented Carbides

Plastic zones much larger than previously expected have been observed around cracks in several cemented carbide materials. A preliminary estimate of the crack tip shielding due to the plastic zone in one material suggests that a substantial fraction of the fracture toughness may be due to the zone. Moreover, reduced zone sizes were observed in regions of rapid crack growth, implying that the dynamic fracture toughness may be smaller than the quasi-static value.     

Toughening of a Particulate-Reinforced Ceramic-Matrix Composite by Thermal Residual Stress

The micromechanics involved in increased crack growth resistance, K _R, due to the addition of TiB₂ particulate in a SiC matrix was analyzed both experimentally and theoretically. The fractography evidence, in which, the advancing crack was attracted to adjacent particulates, was attributed to the tensile region surrounding a particulate. Countering this effect is the compressive thermal residual stress, which results in the toughening of the composite, in the matrix. This thermal residual stress field in a particulate-reinforced ceramic-matrix composite is induced by the mismatch in the coefficients of thermal expansion of the matrix and the particulate when the composite is cooled from the processing to room temperature. The increase in K _R of the composite over the monolithic matrix, which was measured by using a hybrid experimental-numerical analysis, was 77%, and compared well with the analytically predicted increase of 52%. The increase in K _R predicted by the crack deflection model was 14%. Dependence of K _R on the volume fraction of particulates, f _p, and of voids, f _v, is also discussed.     

Ti(C0.3N0.7)-Si3N4复合材料的制备与性能

在Si3N4基体材料中添加高弹性模量的第二相粒子Ti(C0.3N0.7),研究第二相的引入对氮化硅陶瓷材料力学性能的影响.结果表明,在Si3N4基体材料中添加Ti(C0.3N0.7)能起到弥散颗粒增韧的作用.     

热固性树脂的刚性增韧Ⅰ、环氧-聚砜体系的断裂韧性及其增韧机理

用斜削双悬臂梁试件测试环氧-聚砜体系的断裂韧性(G_IC)表明:该体系有较高的G_IC值,并且G_IC与G_Ia相近,也就是其断裂韧性与止裂韧性相当;比较该体系G_IC的温度谱和动态力学性能(DMA)的温度谱说明,该体系韧性与其粘弹性有关;分析扫描电镜(S-M)的照片可以看出,该体系由韧性聚合物的连续相包络热固性树脂固化球粒,即“网络-球粒”结构,这种结构是导致该体系高韧性的原因。     

Rubber phase dispersion in polypropylene

Impact properties of rubber-modified blends are significantly dependent on particle size and size distribution (dispersion). Past work has shown strong variations in these particle parameters with different processing conditions and these variations reflect, in part, different shear fields developed during melt extrusion and moulding. A major problem ensues involving property variability because of process variability. It is neither practical nor economical to place stringent controls on process variability in a plant. Instead, our current research has indicated that lightly crosslinking the rubber reduced drastically the sensitivity of dispersion to processing conditions, and, with the correct rheology between the rubber and the resin, the same dispersion could be maintained through both the extrusion and moulding stages resulting in finished parts with increased chance of dispersion and property consistency. Four rubbers of different degrees of crosslinking and three polypropylenes of different melt flow and structure were blended at six rubber levels. Mixing was carried out with two twin-screw configurations and the blends were cast or injection moulded using a ram or a screw moulder representing six different processing shear histories. Dispersion was quantitatively characterized by scanning electron microscopy (SEM). Spherical rubber particles revealed on the fracture surface were counted and measured to determine particle size and size distribution for the individual blends. Correlation of the results indicated how particle size and size distribution was influenced by crosslinking and the rubber/resin rheology. This provided some understanding of the mechanics of soft-phase dispersion in these blends.     

PVC/超细二氧化硅复合材料的制备及其性能研究

用沉淀法制备了超细二氧化硅粉体。研究了纳米二氧化硅溶胶的最佳沉淀率和不同偶联剂用量、不同二氧化硅添加量对材料力学性能的影响。结果表明：经表面处理后的超细二氧化硅可以有效改善PVC的力学性能。     

硅氧烷预聚体改性热塑性酚醛树脂的交联结构及其力学性能

通过不同预聚程度的环氧化硅氧烷（ES）与酚醛树脂共固化及固化物理状态的调控,构建不同拓扑结构的交联网络,探讨了不同预聚程度的硅氧烷预聚体（PES）改性热塑性酚醛树脂（NR-PES）交联网络的调控及其强韧化的构建方法。首先,合成了一种不同预聚程度的环氧化硅氧烷（PES）,通过DSC和流变分析,明确了NR-PES的固化反应和物理状态特征,在此基础上,确定了不同交联结构NR-PES的制备方法。接着,采用DMA、TGA、力学测试研究了PES的预聚程度对NR-PES交联网络和性能的影响规律。结果表明,当PES预聚程度较低时,NR-PES的交联密度较低,导致其热稳定性和弯曲强度较低;随着PES预聚程度的增加,NR-PES的交联密度不断增加,其热稳定性、弯曲强度随之增加,但K_IC不断降低。特别是,PES的预聚程度为30%时,2-NR-PES展现出优异的热稳定性、弯曲强度和断裂韧性,残炭率C_800℃为53.43%,弯曲强度为20.51 MPa,K_IC为0.389 MPa·m^1/2。此外,当PES预聚程度过高时,NR-PES的热稳定性、弯曲强度和断裂韧性显著降低。