复合材料静压痕与落锤冲击初始损伤对比试验

为了研究复合材料层合板的分层起始载荷,对不同材料体系和不同铺层数的复合材料层合板进行了准静态压痕试验和落锤冲击试验.得到了复合材料层板的分层起始载荷和冲击分层损伤能量门槛值,并对损伤情况进行了分析.结果表明,层合板的落锤冲击试验的分层起始载荷与冲击能级有关,并且分层起始载荷值随冲击能级提高而增加;准静态压痕试验的分层起始载荷值要低于低速冲击试验的分层起始载荷值;当冲击能量达到层板分层损伤能量门槛值时,层板发生大量分层损伤,层合板刚度出现急剧下降.     

对接机构地面仿真试验误差综合方法研究

对仿真试验中仿真误差的综合是给出判断仿真结果的准确度和可信度依据的重要手段。针对在对接机构半实物仿真综合试验台上进行的对接机构的地面仿真试验,提出了一种基于Ｍｏｎｔｅ－Ｃａｒｌｏ方法的误差综合方法;并通过大量的仿真模拟,得出了对接机构地面仿真试验结果的统计规律;给出了仿真结果的置信区间与置信度。此结果可为评定仿真结果的准确性和可信性提供依据。     

基于属性权重的关系数据库数字指纹算法

分析了在数字指纹系统中引入属性的必要性和可行性。介绍了基于属性权重的关系数据库数字指纹算法,适用于版权保护中的叛逆者追踪。通过把重要的属性赋予高的权重确保实现重要的属性多水印。最后,就抗同谋攻击等分析了算法的性能。实验证明该算法对于各种常见的攻击具有较好健壮性。     

B/Al复合材料的制造、性能及应用

综述了国内外B/Al复合材料的发展研究现状 ,具体介绍了几种制备技术的基本原理和工艺 ,包括热压扩散法、熔体浸渗法等。从工艺的角度分析了复合工艺参数———温度、时间、压力和环境对B/Al复合材料及对B纤维的影响。对B/Al复合材料的力学性能和在航空航天等方面的应用也做了较为系统的介绍 ,分析认为国内采用热压扩散法制备的B/Al复合材料性能稳定 ,其管材、型材已达到了应用阶段 ,为我国航空航天技术中应用此类复合材料奠定了基础     

航空发动机压气机叶片砂尘冲蚀防护涂层关键问题综述

军用直升机和运输机沙漠作战时,砂尘被高速吸入发动机导致压气机叶片外形和结构完整性遭到破坏,严重影响作战性能和耐久性。涂层是提高压气机叶片抗砂尘冲蚀能力的有效措施,但涂层的防护能力与涂层的服役环境、材料体系、结构成份、制备技术以及考核体系等密切相关。结合美军在西亚沙漠作战直升机压气机受损严重的问题,从涂层设计指导性、制备技术可实现性以及试验考核体系的完备有效性三方面综述和对比国内外抗冲蚀涂层研究发展情况,重点分析涂层环境适应性、材料和结构强韧性、制备方法以及考核体系中的影响涂层防护能力的关键问题,深入剖析我国存在的主要差距和原因。分析表明:机理研究不深入、涂层结构与性能设计研究亟待加强、考核手段不完备、研究系统性不强是制约我国抗冲蚀涂层向应用转化的关键,本文对梳理抗冲蚀涂层领域的发展方向具有十分重要的指导意义。     

屈曲模态对含缺陷复材加筋板后屈曲的影响

某些结构类型的复合材料加筋板,由于一阶和二阶屈曲载荷十分接近,在压缩失稳时,相同的试验件会出现不同的失稳模态,并表现出明显不同的后屈曲承载能力。就此问题,进行了试验和数值模拟研究。轴压试验中,通过影像云纹法和超声C扫技术监测试验件的失稳模态及缺陷扩展情况,以确定不同失稳模态对相同试验件后屈曲承载能力的影响。基于ABAQUS软件建立有限元模型,采用虚拟裂纹闭合技术（VCCT,Virtual Crack Closure Technology）模拟含预置脱胶缺陷的筋条-蒙皮界面,将失稳波形以几何扰动的形式引入后屈曲分析。通过分析缺陷前缘应变能释放率,研究两种模态下缺陷扩展特性。计算结果与试验结果相吻合,研究表明两种模态下缺陷的扩展特性明显不同,导致该型加筋板在3个半波失稳模态下的后屈曲承载能力明显高于2个半波模态下的后屈曲承载能力。     

复合材料开孔层压板压缩长期强度预测

Accelerated testing methodology (ATM) predicts long-term strength in low temperature with short-term in high temperature, which is based on the viscoelasticity of matrix and the time-temperature superposition principle (TTSP). The strain invariant failure theory (SIFT) was modified by using micro maximum strain criteria to judge fiber tensile and compressive failure. Master curve of storage modulus of epoxy resin and the time-temperature shift factors were tested from dynamic mechanical analysis(DMA). Master curves of SIFT critical parameters were constructed by tension and compression test for unidirectional carbon fiber reinforced plastics (CFRP) under various temperatures with the time-temperature shift factors of matrix resin. Long-term compression strength of open-hole composite laminates was predicted based on SIFT/ATM combined method. The damage process of fiber and matrix was simulated by progressive damage analysis as well. Good agreement between numerical results and experiments was observed, which demonstrates the applicability of this method.     

星载GPS数据质量控制方法研究

针对星载全球定位系统（GPS）数据的特点,分别从阈值设置和周跳检验量的角度对TurboEdit方法进行改进,并在传统抗差估计方法的基础上,提出一种改进的抗差估计策略。利用GRACE卫星的星载GPS观测数据对本文的质量控制方法进行分析验证,结果表明：改进的质量控制方法能明显增强周跳探测性能,有效抑制小周跳和粗差的影响,提高几何法定轨的精度和可靠性。     

Chicxulub and climate: radiative perturbations of impact-produced S-bearing gases

We use one-dimensional (1D) atmospheric models coupled to a sulfate aerosol model to investigate climate forcing and short-term response to stratospheric sulfate aerosols produced by the reaction of S-bearing gases and water vapor released in the Chicxulub impact event. A 1D radiation model is used to assess the climate forcing due to the impact-related loading of S-bearing gases. The model suggests that a climate forcing 100 times larger than that from the Pinatubo volcanic eruption is associated with the Chicxulub impact event for at least 2 years after the impact. In particular, we find a saturation effect in the forcing, that is, there is no significant difference in the maximum forcing between the highest (approximately 300 Gt) and lowest (approximately 30 Gt) estimated stratospheric S-loading from the Chicxulub impact. However, higher S-loads increase the overall duration of the forcing by several months. We use a single column model for a preliminary investigation of the short-term climate response to the impact-related production of sulfate aerosols (the lack of horizontal feedbacks limits the usefulness of the single column model to the first few days after the impact). Compared with the present steady-state climate, the introduction of large amounts of sulfate aerosols in the stratosphere results in a significant cooling of the Earth's surface. A long-term climate response can only be investigated with the use of a three-dimensional atmospheric model, which allows for the atmospheric circulation to adjust to the perturbation. Overall, although the climate perturbation to the forcing appears to be relatively large, the geologic record shows no sign of a significant long-term climatic shift across the K/T boundary, which is indicative of a fast post-impact climatic recovery.     

国外高能量密度材料与目标化合物CL—20的进展

介绍了国外高能量密度材料(HEDM)发展的新动态。以多硝基/硝胺基多环化合物和主体笼形化合物等的开发研究作为契机,HEDM发展进入了一个新的阶段。CL-20即六硝基六氮杂异伍兹烷(HNIW)是一个很有前途的多环硝胺主体笼形化合物,本文着重评述它的结构、性能、应用及合成途径。认为通过它的六氮杂前驱物体系的基团转化而引入硝基的途径是可取的。