泡沫夹层结构复合材料热膨胀模压法工艺研究

在传统泡沫夹层结构复合材料成型工艺基础上,探索了一种新型的夹层结构成型工艺。传统工艺需要热压罐、真空袋等外部设备来为成型提供压力,文中提出了利用泡沫本身热膨胀和刚性模具的限制作用,为泡沫夹层结构复合材料提供成型压力。通过对泡沫芯材的模压发泡工艺的控制、监测,分析了夹层结构成型时内部产生压力的大小。同时,对其弯曲强度和剥离强度进行了表征。实验结果表明:控制芯材密度、发泡温度和发泡时间能有效地提高夹层结构的成型压力和力学性能。     

CFRP二面角电磁散射特性分析

用时域有限差分(Finite difference-time domain,FD-TD)法分析计算了由碳纤维复合材料(Carbon fiber reinforced polymer,CFRP)单向板组成的二面角的电磁反射特性.计算结果表明,碳纤维二面角的雷达散射截面(Radar cross section,RCS)对纤维方向和极化方向敏感.当两块板的纤维方向垂直时,对极化方向敏感度降低.     

利用SiO2欧泊制备高比表面积三维有序大孔碳

通过自组装的方法制备了面心立方结构的S iO2欧泊,并利用其为模板,分别采用“体积模板”与“表面模板”两条途径,合成了两类不同结构的三维有序大孔碳材料,分析了填充次数对产物形貌结构的影响。通过场发射扫描电子显微镜和氮气等温吸附-脱附分析对所合成的三维有序大孔碳进行了表征。结果表明:两种结构的碳材料都保持了欧泊的三维有序性,并且具有高的比表面积与孔容。这类材料在催化、分离、吸附以及电极等领域有着广阔的应用前景。     

组合式起落架缓冲器耐坠毁性能仿真与分析

提出了一种油气?泡沫铝组合式直升机缓冲装置,基于塑性坍塌应力理论计算模型和有限元模型对单一泡沫铝冲击压溃应力?应变进行了计算和仿真分析,计算结果和仿真分析结果进行了相互校验.通过单一泡沫铝冲击压溃试验对理论和仿真模型进行了试验验证.将泡沫铝压溃动态特性曲线融入油气?泡沫铝组合式起落架缓冲动力学模型开展耐坠毁性能仿真分析...     

45#钢微动疲劳特性的研究

微动疲劳发生于两零件的接触表面间，紧密接触表面间的微辐滑动是产生微动疲劳的重要因素。微动疲劳导致零部件的强度显著降低，是引发意外失效事故的重要原因之一，因此研究材料的微动疲劳特性具有重要的理论和工程应用价值。本文研究了45^#钢在室温下的微动疲劳特性，通过采用宏观力学试验与微观结构分析相结合的方法探讨了45^#钢微动疲劳破坏的机理。通过对试验结果进行分析，确定了显著影响微动疲劳特性的重要因素，从而加深了对微动疲劳过程的认识，而且其中一些结果可以推广应用到其他材料上去。     

Numerical Modeling of the Compression Process of Elastic Open-cell Foams

The random models of open-cell foams that can reflect the actual cell geometrical properties are constructed with the Voronoi technique. The compression process of elastic open-cell foams is simulated with the nonlinear calculation module of finite element analysis program. In order to get the general results applicable to this kind of materials, the dimensionless compressive stress is used and the stress-strain curves of foam models with different geometrical properties are obtained. Then, the influences of open-cell geometrical properties, including the shape of strut cross section, relative density and cell shape irregularity, on the compressive nonlinear mechani- cal performance are analyzed. In addition, the numerical results are compared with the predicted results of cubic staggering model. Numerical results indicate that the simulated results reflect the compressive process of foams quite well and the geometrical properties of cell have significant influences on the nonlinear mechanical behavior of foams.     

碳纤维增强塑料的强度与碳纤维性能的关系

本文探讨了碳纤维增强塑料的强度与碳纤维性能的关系,结果表明二者关系密切,并指出根据材料在结构中的不同工作条件确定对碳纤维的要求时,应综合考虑对其工作性能起决定性作用的各种因素。     

新生代的气候效应与碳循环

对发生于新生代的６次巨大天体撞击作用（６５Ｍａ，３４Ｍａ，１５Ｍａ，２４Ｍａ，１．１Ｍａ，０．７Ｍａ）的气候效应进行的模拟表明，这６次巨大天体撞击作用产生的尘埃进入平流层后，可使全球平均温度下降至零度以下，降温效应持续时间最长可达３０年之久，首次在模拟中考虑全球性森林大火产生的ＣＯ２和死亡生物分解生成的ＣＯ２的温室效应，研究表明这两种作用使大气中ＣＯ２增量最大仅达６７％，其增温效应远远低于尘埃层产     

Fabrication of Diamond-like Carbon Films by Ion Assisted Middle Frequency Unbalanced Magnetron Sputtering

Diamond-like carbon (DLC) films are deposited by the Hall ion source assisted by the mid-frequency unbalanced magnetron sput-tering technique. The effects of the substrate voltage bias, the substrate temperature, the Hall discharging current and the argon/nitrogen ratio on the DLC film’s performance were studied. The experimental results show that the film’s surface roughness, the hardness and the Young’s modulus increase firstly and then decrease with the bias voltage incrementally increases. Also when the substrate temperature rises, the surface roughness of the film varies slightly, but its hardness and Young’s modulus firstly increase followed by a sharp decrease when the temperature surpassing 120 ℃. With the Hall discharging current incrementally rising, the hardness and Young’s modulus of the film decrease and the surface roughness of the film on 316L stainless steel firstly decreased and then remains constant.     

Study on Microwave Dielectric Property of Carbon Black and Short Carbon Fibers

Carbon black and carbon fibers of different lengths were introduced in different matrices at different ratios to explore their microwave dielectric properties under 8.2 GHz-12.4 GHz. It is found that the actual dielectric constants of the samples containing carbon black are in a two-order function of the contents of carbon black （ε＇, ε＂=Av2＋Bv＋C） and the complex dielectric constants show an obvious frequency response. Of the added fibers of different lengths, the 4 mm-long one could well disperse in the matrices having not only good frequency response, but also larger real parts, imaginary parts and loss values. The imaginary parts and the loss values （tanδ）of the samples with 4 mm-long carbon fibers added increase linearly with the contents of fiber increasing. So it is practicable to adjust the dielectric parameters of the material in a wide range by changing the added amount of carbon black, and the carbon fiber or altering the lengths of the carbon fiber added.