3D C/C复合材料的电弧驻点烧蚀及机理分析

采用电弧驻点烧蚀试验方法,测试细编穿刺毡增强体C／C复合材料的烧蚀率,并采用电子扫描显微镜观察烧蚀表面形貌。研究结果表明:在电弧驻点烧蚀试验条件下,3D C／C复合材料具有较好的烧蚀性能;C／C复合材料的烧蚀过程主要受热化学烧蚀和机械剥蚀2种烧蚀机制的共同作用,二者相互促进,以机械剥蚀为主;微观烧蚀形貌主要由热化学化蚀导致,宏观烧蚀形貌则主要是机械剥蚀所致。     

CPP/PLLA软骨组织工程支架复合材料降解性能研究

采用溶媒浇铸/粒子滤取技术与气体发泡相结合的方法制备出CPP/PLLA软骨组织工程支架复合材料,测试了该支架复合材料的物理力学性能和降解性能.研究结果表明,CPP/PLLA软骨组织工程支架复合材料具有适宜的孔隙率,良好的降解性能和物理力学性能,以及三维连通、微孔、网状微观结构.因此,该复合材料有望成为软骨组织工程支架材料之一.     

用于模拟压电复合材料平面问题的边界点法

针对含规则形状夹杂的压电复合材料平面问题,将边界点法和重复相似子域法相结合,实现了一种用于含有大量圆形夹杂的横观各向同性压电复合材料的分析方法,并通过相应的计算模型求得压电复合材料的等效材料性质。数值算例表明该方法具有很高的精度和一定的可行性。由于边界点法具有高精度的特性以及对所有的内部夹杂边界进行离散,因此很容易将该文方法扩展应用到分析含任意形状夹杂的压电复合材料。     

仿生物矿化过程合成无机/有机复合体研究

仿生材料目前是各国科学家关注的焦点,理论与实验研究已经取得很大进展。本文主要对模仿生物矿化过程合成无机/有机复合体进行了综述。     

Cu-11Fe-4Cr原位复合材料在HSO^-3和／或C1^-介质中的耐蚀性

采用选择腐蚀技术，提取了Cu-11Fe-4Cr原位复合材料中Fe-Cr纤维，并测定了其电极电位。通过间歇式盐水喷雾实验和极化曲线测定，研究了Cu-11Fe-4Cr原位复合材料在HSO^-3和／或C1^-介质中的腐蚀行为。用扫描电镜对腐蚀产物和腐蚀表面进行分析。结果表明，Cu-11Fe-4Cr原位复合材料中，E（Cu）〈E（Fe-Cr），故Cu基体为阳极，而第二相Fe-Cr纤维为阴极。Cu-11Fe-4Cr原位复合材料在（NaHS03＋NaC1）和NaHS03介质中的E（Fe-Cr）-E（Cu）显著高于NaC1介质中的E（Fe-Cr）-E（Cu），Cu-11Fe-4Cr原位复合材料在NaC1介质中的腐蚀失重最小，在NaC1介质中具有良好的耐蚀性。     

再生橡胶改性高强混凝土性能试验研究

以废轮胎橡胶粉作为改性材料，研究了橡胶粉含量和细度对高强混凝土密度、坍落度、抗压强度、劈裂抗拉强度和抗折强度的影响。研究表明：随着橡胶粉掺量的增加，橡胶粉高强混凝土材料的密度、坍落度、强度会下降。橡胶粉的粒径对高强混凝土的抗压强度、抗折强度影响不明显，但劈裂抗拉强度就随着橡胶粉粒径的增大而下降。     

氯丁橡胶/丁基橡胶的成形工艺研究

选用CR1211和IIR1751为生胶原料,以氧化锌/氧化镁和硫磺为硫化体系,二氧化硅和白炭黑为补强剂,经混炼、硫化等加工过程,研究了CR1211和IIR1715并用橡胶的成形工艺。结果表明,当IIR投料顺序在先时,混炼较容易,硫化胶的力学性能优异,稳定性好,当CR1211和IIR1715投料比为1∶1时,硫化橡胶强度和热性能都较好。同时还发现,硫化橡胶强度随硫化温度升高而下降,合适的硫化条件为160℃,10.5 min。     

Adhesion of PBO Fiber in Epoxy Composites

The high mechanical and thermal performance of poly p-phenylene- 2, 6-benzobisoxazole ( PBO ) fiber provides great potential applications as reinforcement fibers for composites. A composite of PBO fiber and epoxy resin has excellent electrical insulation properties, therefore, it is considered to be the best choice for the reinforcement in high magnetic field coils for pulsed magnetic fields up to 100 T.However, poor adhesion between PBO fiber and matrix is found because of the chemically inactive and/or relatively smooth surface of the reinforcement fiber preventing efficient chemical bonding in the interface, which is a challenging issue to improve mechanical properties. Here, we report the surface modification of PBO fibers by ultraviolet (UV)irradiation, O2 and NH3 plasma, as well as acidic treatments. The interfacial adhesion strength values of all the treatments show the similar level as determined for aramid fibers by pull-out tests, a significant impact on fibermatrix-adhesion was not achieved. The surface free energy and roughness are increased for both sized and extracted fibers after plasma treatments together with maleic anhydride grafting. The sized fiber shows marginal improvement in adhesion strength and no change in fiber tensile strength because of the barrier effect of the finish.For the extracted fiber, different surface treatments either show no apparent effect or cause reduction in adhesion strength. Atomic force microscopy (AFM) topography analysis of the fracture surfaces proved adhesive failure at the fiber surface. The fiber surface roughness is increased and more surface flaws are induced, which could result in coarse interface structures when the treated fiber surface has no adequate wetting and functional groups. The adhesion failure is further confirmed by similar adhesion strength and compression shear strength values when the fiber was embedded in various epoxy resins with different temperature behavior. The tensile strength of fiber is sensitive to surface treatment conditions as revealed by a bimodal Weibull statistical distribution analysis. Considerable strength reduction occurred, particularly for cases of acidic and plasma treatments, while UV irradiation shows the better ability to retain fiber strength.     

Synthesis of novel superhard materials under ultrahigh pressure

Superhard materials are solids whose Vickers hardness is beyond 40 GPa. They have wide applications in industry such as cutting and polishing tools, wear-resistant coatings. Most preparations of superhard materials are conducted under extreme pressure and temperature conditions, not only for scientific investigations, but also for the practical applications. In this paper, we would introduce the recent progress on the design and preparations of novel superhard materials, mainly on nanopolycrystalline diamond, B–C–N superhard solid solutions, and cubic-Si3N4/diamond nanocomposites prepared under ultrahigh pressure and high temperature（HPHT）, using multi-anvil apparatus based on the hinged-type cubic press. Bulk materials of all these superhard phases have been successfully synthesized and are systematically tested. We emphasize that ultra-HPHT method plays an important role in the scientific research and industrial production of superhard materials. It provides the driving forces for the light elements forming novel superhard phases as well as the way for sintering high-density nanosuperhard materials.     

Transition from Multiple Macro-Cracking to Multiple Micro-Cracking in Cementitious Composites

This paper presents an experimental study of the possibility of transition from multiple macro-cracking to multiple micro-cracking in cementitious composites.Conventional polyvinyl alcohol fiber reinforced cementitious composites normally exhibit macroscopic strain-hardening and multiple cracking after the first cracks appear.However,the individual crack width at the saturated stage is normally 60 to 80 μm.In the current study,the effect of fine aggregate size on the cracking performance,especially the individual crack width in the strain-hardening stage was studied by bending tests.The results show that the individual crack widths can be reduced from 60-80 μm to 10-30 μm by modifying the particle size of the fine aggregates used in the composites.