关键词： Short-fiber composites   Textile composites   Mechanical properties   Additive manufacturing  

摘要： In contrast to conventional preforming techniques, additive manufacturing features direct and layer-by-layer fabrication, which provides viable new capabilities for the fabrication of reinforced composites. In this article, we explore the microstructural design as well as additive manufacturing and characterization of 3D orthogonal, short carbon fiber/acrylonitrile-butadiene-styrene (ABS) preforms and composite. First, an array of 3D orthogonal preforms is designed based on topological consideration and validated by fused filament fabrication of pure ABS wire;high fidelity between models and preforms is accomplished. Then, short carbon fibers are introduced into the designed 3D orthogonal preforms as reinforcement, using a short carbon fiber/ABS wire. Lastly, the compressive behavior of a 3D orthogonal, short carbon fiber/ABS preform and that of its silicone infused composite are characterized. The preform design methodology developed in this research as well as the preliminary effort made in composite fabrication and characterization demonstrates the feasibility of additive manufacturing of 3D orthogonal preform based fiber composites. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： 能量法   材料微结构   极限弹性性能   拓扑优化   SIMP插值  

摘要： 基于应变能等效的能量法,求解材料微结构的等效弹性系数矩阵,以等效弹性系数矩阵主对角线上元素的某项或某几项的加权组合最大为目标,以材料体积率为约束,构建具有极限弹性性能材料微结构的拓扑优化模型,采用SIMP插值结合优化准则法求解该优化模型,推导了优化求解过程中的敏度表达式,实现了具有极限弹性性能的材料微结构拓扑构型设计.数值算例验证拓扑优化模型和算法的有效性.

关键词： 水化硬化机理   水泥基材料   构形   中国硅酸盐学会   南召   学术交流   物理力学性能   研讨内容  

摘要： 为了促进学科发展，充分发挥中国硅酸盐学会的学术交流优势和《硅酸盐学报》作为开展学术交流、学术争鸣重要阵地的作用，定于2016年8月14日～16日在山东省济南市举办水泥基材料水化硬化机理与微结构形成研讨会，研讨内容为：水泥基材料的组成、水化硬化机理、微结构形成及其与物理力学性能的关系。

关键词： 纳米镁铝水滑石   微结构   生长机理   吸附  

摘要： 本文以硝酸镁、硝酸铝为原料,以碳酸钠和氢氧化钠为沉淀剂和pH值调节剂,采用液相沉淀法制备了纳米镁铝水滑石层状化合物(Mg-Al-LDHs),利用X射线衍射(XRD)、扫描电镜(SEM)及X射线能谱分析仪(EDS)系统比较研究了pH值、反应温度、镁铝比等条件对合成LDHs晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其生长机理进行了初步探讨,在此基础上,以甲基橙(MO)模拟染料废水为吸附对象,考察了最佳条件下制备的LDHs培烧产物的吸附性能和吸附机理。研究结果表明:pH值、温度的增加有利于生成结构单一、结晶性、规整性较好的镁铝水滑石晶体,产物晶粒尺寸及径厚比呈增大趋向。当反应温度等于或大于80℃时,温度的升高对镁铝水滑石晶体的形态影响较小。镁铝比的改变对产物的物相影响较小,但影响产物的结晶及生长,当镁铝比为3∶1时,所得产物晶粒的规整度、均一性最好,尺寸约为70-100 nm,厚度为20 nm左右,镁铝比为1∶1时,晶粒粒径明显减小,约为30 nm左右。最佳条件下合成的纳米镁铝水滑石焙烧产物具有较好的吸附性能,随着时间的增加,吸附脱色率逐渐增加,当吸附时间达到70 min,LDO对染料的吸附逐渐达到饱和平衡,脱色率达到90%以上,吸附动力学研究表明LDHs对甲基橙的吸附过程更符合准一级动力学方程,其R2值更接近1,吸附等温线符合Langmuir模型。

关键词： Microstructure   MIP   Road pavement   Salinity   Salt crystallization   SEM  

摘要： Areas of high environmental salinity are predicted to increase over the next 40 years in Australia, due to land use and climatic changes. This presents a risk to road assets as accumulation of salts within roads has been found to cause damage to thin bituminous surfacings. It is in this context that the present study explores the microstructural changes caused by environmental salt crystals accumulating within unbound granular road pavements. Fine-grained specimens were prepared by static compaction, immersed in different solutions, and finally either freeze-dried or oven-dried at 40 degrees C. The effects of different drying procedures and salinity on soil's microstructure were explored via mercury intrusion porosimetry and scanning electron microscope observation. Results suggest that a freeze-drying process can significantly modify the microstructure, which should be taken into account when conducting any microstructural analysis on high-salinity soil specimens.

关键词： Microhardness   Precipitation   Steel   Carbide  

摘要： Nanometer-sized carbides that precipitated in a Ti-Mo bearing steel after interrupted continuous cooling in a temperature range of 620-700 degrees C with or without hot deformation were investigated by field -emission -gun transmission electron microscopy. The nanometer-sized carbides were identified as randomly homogeneous precipitation carbides and interphase precipitation carbides coexisting in the ferrite matrix. It is found that this dual precipitation morphology of carbides in the steel leads to the non -uniform mechanical properties of individual ferrite grains. Vickers hardness data mainly revealed that, in the specimens cooled at a rate of 0.5 degrees C/s without hot deformation, the range of Vickers hardness distribution was 230-340 HV 0.1 when cooling was interrupted at 680 degrees C, and 220-360 HV 0.1 when cooling was interrupted at 650 degrees C For the specimens cooled at a rate of 0.5 degrees C/s with hot deformation, the range of Vickers hardness distribution was 290-360 HV 0.1 when cooling was interrupted at 680 degrees C, and 280-340 HV 0.1 when cooling was interrupted at 650 degrees C Therefore, a narrower range of hardness distribution occurred in the specimens that underwent hot deformation and were then cooled with a lower interrupted cooling temperature. The uniform precipitation status in each ferrite grain can lead to ferrite grains with a narrower Vickers hardness distribution. On the other hand, interrupted cooling produced a maximum Vickers hardness of 320-330 HV 0.1 for the hot deformed specimens and 290-310 HV 0.1 for the non -deformed specimens with cooling interrupted in the temperature range of 660-670 degrees C. The maximum Vickers hardness obtained in such a temperature range can be ascribed to the full precipitation of the microalloying elements in the supersaturated ferrite matrix with a tiny size (similar to 4-7 nm). (C) 2016 Elsevier Inc. All rights reserved.

关键词： Biopolymer blend   Imperfect interface   Microstructure   Elasticity behaviour  

摘要： The underlined microstructure of biopolymer blends reflects complexity of mass and heat transfer during processing. In the present work, such complexity is apprehended using simple and intuitive way to generate typical microstructures resulting from thermomoulding processing. The starting point is a simple generation scheme of the feed powder approximated as circular heat sources. Finite element computation of a transient thermal analysis is performed and the resulting nodal fields are again converted into 2D microstructures. The final microstructures prove to be similar in all geometrical characteristics starch-zein blends. Elasticity response of these blends is explored using finite element computation. Sensitivity analysis is performed to derive the effect of perfect and imperfect interface properties on the mechanical performance of the biopolymer blend. Predictions show a significant role of interfaces which trigger the elasticity properties of the biopolymer blends much larger than the contrast in phase properties. This study demonstrates that nonlinear interface effect on elasticity behaviour is related to geometrical percolation that occurs at specific phase content. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Steels   Quenching and partitioning   Mechanical properties   Fracture toughness   Crack tip opening displacement   Crack growth resistance  

摘要： Quenching and partitioning (Q&P) is receiving increased attention as a novel heat treatment to produce advanced high strength steels (AHSSs) containing martensite/retained austenite mixtures, with desirable combination of strength, ductility and toughness. Despite the significant body of research on microstructure and mechanical properties of Q&P steels, there is still a significant lack of knowledge on the effect of complex microstructure on their mechanical performance. This work addresses the effect of microstructural architecture in multiphase Q&P steels on their fracture behavior at macro- and micro scales. It is demonstrated that the RA volume fraction does not affect significantly the local fracture initiation toughness, whereas it can greatly improve the total crack growth resistance in Q&P steels. In addition, matrix conditions can play an important role in the fracture behavior of Q&P steels. Based on the analysis of the experimental results, a general recipe to tailor fracture properties of Q&P steels is proposed. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Electron energy loss spectroscopy   Electron diffraction   Collapse of layered structure   High resolution (S)TEM   LiNi0.6Co0.2Mn0.2O2   Li-ion batteries  

摘要： Electrochemical performance of lithium ion batteries is associated with structural and chemical stability of electrode materials. In the case of nickel-rich layered cathode materials LiNi0.6Co0.2Mn0.2O2, cation mixing, which results from the migration of transition metal ions into vacant lithium sites, is accelerated owing to similar ionic radii between nickel and lithium. However, the inevitable lattice distortions and chemical evolution have not been investigated intensely. In this paper, we report the structural evolution localized at surface regions through electron diffraction and high resolution imaging analyses with aberration-corrected transmission electron microscopy and scanning transmission electron microscopy. Repetition of volumetric change generates cracks and voids associated with deterioration of electrochemical performance. Structural change is related with (003) intensity in electron diffraction and it can be presented by dark field transmission electron microscopy imaging at a glance. Drastic structural degradation during early cycling shows relation with rapid capacity and voltage fade. Electron energy loss spectroscopy elucidates that the structural evolution caused by the migration of Ni ions accompanies chemical modification of Mn ions and creation of hole states at the O2p level. This study provides an insight into correlating structural and chemical evolution with degradation mechanism on battery performances of LiNi0.6Co0.2Mn0.2O2 cathode materials. (C) 2016 Elsevier B.V. All rights reserved.

关键词： 多孔压电驻极体   孔洞微结构   拓扑优化   渐近均匀化  

摘要： 多孔压电驻极体是带有分布电荷的孔洞聚合物材料,是一种新型的压电材料.多孔压电驻极体材料的宏观压电性与内部孔洞微结构的构型和分布密切相关.将多孔压电驻极体材料看成含周期微结构的复合材料,采用渐近均匀化理论求解宏观等效系数性质,基于变密度法和拓扑优化方法,利用ANSYS的APDL参数化设计语言编制基于有限元分析的优化程序,给出最优的孔洞微结构拓扑,获得最大压电系数.