关键词： Discontinuous curved fiber reinforced composites (DCFRCs)   Representative volume element (RVE)   Modified RSA algorithm   Modified rule-of-mixture   Elastic properties   Fiber waviness  

摘要： The present study proposes a modified random sequential absorption (RSA) algorithm to generate a representative volume element (RVE) model for predicting the elastic properties of discontinuous curved fiber reinforced composites (DCFRCs) with varying fiber waviness functions and orientations. A small-move method was proposed to modify the traditional RSA algorithm. In comparison with the original RSA algorithm, the generation efficiency of the proposed modified RSA algorithm increased by over 40%, and the achievable maximum fiber volume fraction could reach up to 15% with a fiber aspect ratio of 15. The generated RVE model was utilized in conducting finite element analysis to investigate the effect of fiber waviness and wavy functions on the elastic properties of DCFRCs. Finally, a modified rule-of-mixture was proposed to predict the elastic properties of DCFRCs with various fiber orientations. The results indicated that the elastic properties predicted by the modified rule-of-mixture were in good agreement with those obtained from the RVE model, thereby demonstrating its effectiveness.

关键词： High-G droplets   Composite substrate   Wetting profile   Hypergravity condition   Scaling law   Energy distribution  

摘要： The wetting phenomenon of composite substrates in hypergravitational environment has a huge application in electronic devices and astronaut healthcare in aerospace missions. In the present contribution, the governing equation of high-G droplets on the composite substrate is firstly established in the hypergravitational environment. Meanwhile, the apparent contact angles at the contact line between droplets and substrates with different stiffness gradients are achieved. Then, we analyze the effects of hypergravity factor and the substrate stiffness on the wetting profile of high-G droplets. By introducing the droplet volume and contact angle into the Bond number, the scaling law of the high-G droplet profile is established, and we find that the contact radius of the droplet R/S-0.5 has a linear relationship with rho omega(2)rl(2)S/(gamma(LV)theta), while the droplet height H/S-0.5 has a power-law relationship with rho omega(2)rl(2)S / (gamma(LV)theta). Finally, we explain the profiles of high-G droplets during the wetting process by illustrating energy components of the entire system and find that the substrate with positive triangular stiffness and inverted triangular stiffness show opposite evolution laws. On a substrate with inverted triangular stiffness, the gravitational potential energy is more dominant.

关键词： Porous metal-matrix nanocomposite   Graphene nanoplatelets   Rotating microbeams   Modified couple stress theory   Dynamics   Thermal buckling  

摘要： A comprehensive dynamic model for thermal buckling, elastic vibration and transient response analysis of rotating nano-composite porous metal-matrix microbeams reinforced with graphene nanoplatelets (GNPs) under a uniform thermal gradient is proposed. Various pore distribution patterns are considered together with different GNPs dispersion rules according to the specific functions. The extended rule of mixture and Halpin-Tsai micromechanics model are employed to evaluate the effective material properties of the nanocomposites. Based on the modified couple stress theory and the improved third-order shear deformation theory, the dynamic equations of the rotating microbeam are established by the Lagrange's equation. The Chebyshev-based Galerkin method is adopted to discretize these equations, which are then solved by the complex modal analysis and Runge-Kutta-Merson method. Convergence study and comparisons with previous literature are conducted for validation of the present method. A parametric study performed analyzes the effects of angular velocity, thickness-to-length scale parameter ratio, porosity coefficient, weight fraction and geometry of GNPs together with distribution patterns of GNPs and pore on the critical buckling temperature rise, fundamental frequency and time-dependent response of the rotating nanocomposite microbeams. The results reveal significant effects of these parameters on the relevant mechanical behaviors, some of which are even contrary to expectations. Therefore, it is necessary to further study this kind of rotating nanocomposite structures for the optimal design.

关键词： 纳米金颗粒   介孔二氧化硅   钛表面改性   微纳结构   高糖条件   成骨分化  

摘要： 背景:微纳米结构改性是钛种植体表面处理的热点研究领域。糖尿病高血糖环境会影响钛种植体与骨组织形成稳定的结合,探索通过表面微纳结构改性来提高钛种植体在高糖环境下的成骨活性是有必要的。目的:观察钛表面纳米金颗粒@介孔二氧化硅涂层对体外高糖条件下成骨分化的影响。方法:分别制备纳米金颗粒悬浮液与介孔二氧化硅,将二者按一定比例混合在去离子水中,制备纳米金颗粒@介孔二氧化硅悬浮液。取钛片,分3组处理:光滑组经过水砂纸打磨处理,纳米管组经过水砂纸打磨处理后采用阳极氧化技术制备二氧化钛纳米管涂层,实验组制备二氧化钛纳米管涂层后浸泡于纳米金颗粒@介孔二氧化硅悬浮液中,制备纳米金颗粒@介孔二氧化硅涂层,表征3组钛片表面的微观形貌、亲水性。将大鼠骨髓间充质干细胞接种于3组钛片表面,通过细胞活/死荧光染色及CCK-8实验检测细胞增殖,DAPI/鬼笔环肽染色检测细胞黏附。将大鼠骨髓间充质干细胞接种于3组钛片表面,加入高糖成骨诱导培养基培养,通过碱性磷酸酶与茜素红S染色检测成骨分化。结果与结论:(1)扫描电镜下可见光滑组钛片表面均匀平坦,纳米管组钛片表面排列紧密的二氧化钛纳米管阵列,实验组钛片在二氧化钛纳米管表面及内部均负载纳米金颗粒@介孔二氧化硅;纳米管组、实验组钛片亲水性均优于光滑组。(2)细胞活/死荧光染色结果显示,3组钛片表面的细胞活力均高于90%;CCK-8实验结果显示,实验组细胞增殖率高于光滑组、纳米管组;DAPI/鬼笔环肽染色结果显示,二氧化钛纳米管涂层、纳米金颗粒@介孔二氧化硅涂层更有利于细胞黏附。(3)碱性磷酸酶与茜素红S染色结果显示,实验组钛片表面细胞碱性磷酸酶活性与细胞外基质矿化程度均高于光滑组、纳米管组。(4)结果表明,纳米金颗粒@介孔二氧化硅涂层可增强钛表面生物活性,促进高糖环境下的成骨分化。

关键词： Ti-Ta基复合材料   表面纳米化   表面机械碾磨处理   抗辐照性能   力学性能  

摘要： 对Ti-Ta基复合材料进行表面机械碾磨处理,有望提高材料的抗辐照性能和力学性能,借助XRD、SEM、TEM从微观组织、晶粒尺寸等方面分析SMGT对Ti-Ta基复合材料表面纳米化效果的影响。利用显微硬度计和拉伸试验机验证强化效果,通过断口观察分析断裂机理。实验结果表明,经SMGT处理后在Ti-Ta基复合材料表层形成梯度纳米结构,其中外表层晶粒尺寸最小约为12.1 nm,塑性变形机制为位错切割机制。SMGT后Ti-Ta基复合材料的显微硬度和抗拉强度最高可达440 HV和1097.528 MPa。

关键词： 生物基环保塑料   复合材料   制备工艺   性能优化  

摘要： 随着全球对环境保护和可持续发展的重视,传统石油基塑料因其不可降解性和对环境的长期污染问题,已难以满足现代社会对环保材料的需求。生物基环保塑料复合材料作为一种新型材料,以其独特的优势逐渐受到广泛关注。该类材料不仅来源于可再生资源,如农作物、林业废弃物、微生物等,而且在使用过程中可自然降解,对环境友好。基于此,本文首先阐述生物基环保塑料复合材料的定义与分类,其次,分析生物基环保塑料复合材料的制备工艺,最后阐述生物基环保塑料复合材料的性能优化,以供参考。

关键词： 纳米金刚石   聚己内酯   磷脂   溶液浇铸法   MC3T3-E1细胞   成骨分化   骨组织工程  

摘要： 背景:聚己内酯因具有良好的加工和降解性能在骨组织工程中得到广泛应用,但其较差的亲水性及机械强度并不能为成骨细胞提供良好的生长环境。目的:制备聚己内酯/纳米金刚石-磷脂复合材料,评估其生物相容性和体外促成骨分化能力。方法:使用磷脂对纳米金刚石进行改性,以聚己内酯为原材料,采用溶液浇铸法制备含不同质量比例(0%,2.5%,7.5%,10%)纳米金刚石-磷脂的聚己内酯/纳米金刚石-磷脂复合膜,使用聚己内酯/纳米金刚石膜进行对比,通过对各组材料表面形貌、元素组成、力学性能及水接触角的观察,选取理化性能较佳的复合膜。将MC3T3-E1细胞分别接种于纯聚己内酯膜、聚己内酯/7.5%纳米金刚石-磷脂膜及聚己内酯/7.5%纳米金刚石膜,检测细胞增殖、黏附及成骨分化能力。结果与结论:①通过扫描电镜及表面元素组成证实聚己内酯/纳米金刚石-磷脂复合膜制备成功,与纯聚己内酯膜相比,聚己内酯/7.5%纳米金刚石-磷脂膜的拉伸强度提高了86.06%,弹性模量提高了54.76%,水接触角降低至70.0°,显示出良好的理化性能;②CCK-8检测结果显示,相较于纯聚己内酯膜、聚己内酯/7.5%纳米金刚石膜,聚己内酯/7.5%纳米金刚石-磷脂膜可促进MC3T3-E1细胞的增殖;鬼笔环肽染色显示,相较于聚己内酯/7.5%纳米金刚石膜,纯聚己内酯膜、聚己内酯/7.5%纳米金刚石-磷脂膜上的MC3T3-E1细胞多为菱形或纺锤形纤维状,细胞连接更紧密;碱性磷酸酶染色显示,相较于纯聚己内酯膜、聚己内酯/7.5%纳米金刚石膜,聚己内酯/7.5%纳米金刚石-磷脂膜上的MC3T3-E1细胞展现了更强的成骨分化能力;③结果表明,聚己内酯/纳米金刚石-磷脂复合材料具有良好的力学性能、亲水性、生物相容性及体外促成骨分化能力。

关键词： 纳米混粉   电火花-电解复合加工   SiC_(p)/Al复合材料   小孔加工   加工特性  

摘要： 为实现金属基复合材料的高效加工,以SiC_(p)/Al为工件,采用混入活性剂纳米颗粒的低浓度盐溶液作为工作液,开展纳米颗粒混粉电火花-电解复合加工小孔实验,调整了工作液配比和电加工参数值,研究了电参数如峰值电流、脉冲宽度、脉冲间隔以及不同纳米颗粒、工作液电导率对材料去除率和加工孔锥度的作用规律。结果表明:增加峰值电流和脉宽,可提高材料去除率、降低加工孔锥度;加工孔锥度随着石墨烯、W粉末体积浓度和粒径增加而降低,Al_(2)O_(3)粉末与之相反;石墨烯、W粉末工作液在较高电导率时提高材料去除率,Al_(2)O_(3)粉末工作液的材料去除率最高,加工孔锥度随着电导率增加而增大,证明通过调控工艺参数可有效调控加工效率和加工精度。

关键词： 二氧化硅纳米颗粒   自噬   转录组   Arrdc4基因  

摘要： 为寻找二氧化硅纳米颗粒诱导细胞自噬激活的调控蛋白,用20 nm的二氧化硅纳米颗粒处理大鼠血管内皮细胞株,对细胞样品进行转录组测序分析及试验.根据CCK-8方法测定的细胞死亡率及自噬Marker蛋白的表达量确定诱导时长,由此制备细胞样品并进行转录组测序及分析预测,通过RNA干扰实验筛选具有自噬调控功能的蛋白质.研究结果表明,20 nm二氧化硅纳米颗粒处理细胞的较优诱导时间为24 h,自噬Marker蛋白LC3B-Ⅱ的表达随着纳米颗粒处理时间的增加而增高;在转录组测序结果中共筛选到295个差异表达基因,差异基因的KEGG富集分析结果显示大部分基因参与多个自噬调控信号通路;通过RNA干扰实验和免疫印迹实验验证,结果表明干扰Arrdc4基因的表达可以降低细胞内LC3B-Ⅱ的表达水平.综合考虑所有实验结果,Arrdc4可能通过KEGG显著富集的信号通路影响二氧化硅纳米颗粒诱导的细胞自噬,其调控机制仍有待深入挖掘.

关键词： 不饱和磷酸酯齐聚物   乙烯-醋酸乙烯酯共聚物   耐疲劳性能   低烟无卤阻燃  

摘要： 将不饱和磷酸酯齐聚物(unsaturated polyester oligomer,UPEO)与无机阻燃剂复配,制备了反应型复合无卤阻燃剂(OP-FRC),通过熔融共混法将其引入乙烯-醋酸乙烯共聚物(ethylene-vinyl acetate copolymer,EVA)基低烟无卤阻燃线缆护套材料中,采用热重分析仪、差示扫描量热仪、平行板流变仪、电子万能试验机、扫描电子显微镜、极限氧指数测定仪等研究UPEO对复合材料结构和性能的影响。结果表明,OP-FRC中UPEO的引入可以改善无机阻燃剂在EVA基体中的分散性,增强两者间的相互作用,促进无机填料网络的形成,并提高分子链段的运动能力,促进基体缠结结构的松弛,从而改善复合材料的耐疲劳性能、热稳定性和结晶能力。当UPEO质量分数为4%时,复合材料的断裂伸长率为215.5%,疲劳寿命为26354次,极限氧指数为31.5%。