双向受载裂纹板的碳纤维复合材料补片的胶接修补分析

建立了碳纤维复合材料补片胶接修补双向受载裂纹板的3D有限元模型,分析了补片的单面胶接修补效果,探讨了补片材料、铺层顺序、补片长度及载荷比等对裂纹应力强度因子的影响规律。结果表明:复合材料补片的存在使裂纹板垂直裂纹方向载荷和平行裂纹板方向载荷发生耦合作用,从而影响补片修补效果。平行裂纹方向的压应力可降低裂纹尖端的应力集中因子,而拉应力可提高裂纹尖端的应力集中因子。     

磁控溅射工艺对CrN基复合涂层微观结构及摩擦学性能的影响

采用闭合场非平衡磁控溅射技术在不锈钢基体上制备了不同质量分数Mo的CrMoN复合涂层。采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、能谱仪（EDX）和光电子能谱仪（XPS）,系统分析了CrMoN复合涂层的相结构、表面形貌、成分、原子化合价价态等,结果表明：添加Mo后,CrMoN涂层的择优取向由CrN涂层的（220）转变为（200）,CrMoN涂层中的Mo原子取代了CrN晶格中的Cr原子,形成（Cr,Mo）N置换固溶体。采用Nano Test 600硬度测试仪测定了CrMoN复合涂层的纳米硬度,结果表明：由于CrN相和MoN两种硬相的协同作用,使得CrMoN复合涂层的纳米硬度值增大。采用多功能摩擦磨损试验机测定了CrN涂层及CrMoN复合涂层的摩擦因数,结果表明：CrMoN复合涂层的摩擦因数低于CrN涂层,磨损过程中由于摩擦热反应生成大量MoO3,使得复合膜的摩擦因数降低,起到了一定的润滑效果,降低了磨损量。     

Fabrication and analysis of TIG welding-brazing butt joints of in-situ TiB2/7050 composite and TA2

Lightweight hybrid structures of Al MMCs and titanium alloy dissimilar materials have great prospect in the defence industry application. So, it is necessary to join Al MMCs with Ti metal to achieve this structural design. In this work, in-situ TiB2/7050 composite and TA2 were firstly attempted to join by TIG welding-brazing technique. The result was that the intact welding-brazing butt joint was successfully fabricated. The joint presents dual characteristics, being a brazing on TA2 side and a welding on TiB2/7050 side. At brazing joint side, ER4043 filler metal effectively wets on TA2 under TIG heating condition, and a continuous interfacial reaction layer with 1—3μm is formed at welded metal/TA2 interface. The whole interfacial reaction layers are composed of Ti(AlSi)3 intermetallic compounds (IMCs), but their morphologies at the different regions present obvious distinguishes. The microhardness of the reaction layers is as much as 141—190 HV. At welding joints side, the fusion zone appears the equixaed crystal structure, and the grain sizes are much smaller than those of welded metal, which is attributed to the effect of TiB2 particulates from the melted TiB2/7050 on acceleration formation and inhibiting growth for the new crystal nucleus. The tensile test results show that average tensile strength of the optimal welding-brazing joint is able to achieve 138 MPa. The failure of the tensile joint occurs by quasi-cleavage pattern, and the cracks initiate from the IMCs layer at the groove surface of TA2 and propagate into the welded metal.     

Influence of thickness and projectile shape on penetration resistance of the compliant composite

The present study deals with development of conceptual proof for jute rubber basedflexible composite block to completely arrest the projectile impacting the target at high velocity impact of 400 m/s through numerical simulation approach using finite element (FE) method. The proposed flexible composite blocks of repeating jute/rubber/jute (JRJ) units are modelled with varying thickness from 30 mm to 120 mm in increments of 30 mm and impacted by flat (F), ogival (O) and hemispherical (HS) shaped projectiles. All the considered projectiles are impacted with proposed flexible composite blocks of different thicknesses and the penetration behaviour of the projectile in each case is studied. The penetration depth of the projectile in case of partially penetrated cases are considered and the effect of thickness and projectile shape on percentage of penetration depth is statistically analyzed using Tagu-chi's design of experiments (DOE). Results reveal that the though proposedflexible composite block with thickness of 90 mm is just sufficient to arrest the complete penetration of the projectile, considering the safety issues, it is recommended to use theflexible composite with thickness of 120 mm. The nature of damage caused by the projectile in the flexible composite is also studied. Statistical studies show that thickness of the block plays a prominent role in determining the damage resistance of the flexible composite.     

卫星中心承力筒结构优化设计研究

利用有限元软件ANSYS建立复合材料中心承力筒式卫星平台结构的参数化有限元分析模型,计算了整星结构振动模态,在此基础上对复合材料蜂窝夹层中心承力筒结构分析模型进行简化,在满足结构的强度、变形、振动和屈曲约束条件下,对承力筒结构进行优化设计,并对多种方案进行比较,提出的方法和思路为今后同类结构设计提供了参考。     

基于复合等效可信度加权的Bayes融合评估方法

在小子样试验评估时,为避免大量先验信息湮没实际飞行试验的信息,融合先验补充样本时通常会进行数学相容性检验并加权.首先分析了小子样情形下直接根据数据计算数学相容性可能造成的不稳定性,为改善这种情况,根据不同试验类型的不同试验环境,对不同试验类型下的误差进行分析和折合,定义了物理等效可信度;并结合物理等效可信度和数学相容性检验,得到先验样本的复合等效可信度权重,基于正态逆伽玛分布计算了Bayes融合评估的后验结果;通过比较Bayes估计后验方差与不磁合先验信息的估计后验方差,根据先验信息参与融合后是否能减小后验方差来判断先验样本是否应该参与融合.理论分析和仿真说明,基于复合等效可信度的加权方法是合理的.     

整体缝合夹芯结构复合材料力学性能

所设计的新型整体缝合泡沫夹芯复合材料结构,能够避免一般斜缝方式引起纤维交叉损坏的弊端。采用真空导入模塑工艺制备整体缝合泡沫夹芯结构复合材料,研究缝合结构、缝合方式以及缝合纱线用量对整体缝合泡沫夹芯复合材料平压力学性能和弯曲性能的影响。结果表明,新型缝合结构在保证平压力学性能的同时,相比于垂直缝合结构弯曲破坏载荷提高了94.4%;穿透缝合方式能够显著提高试样的平压强度和弯曲破坏载荷;随着缝合纱线用量的增加,整体缝合泡沫夹芯复合材料的压缩和弯曲性能显著提高。     

基于响应面法的复合材料层合板平面应力强度可靠性分析

针对处于平面应力状态下的复合材料层合板，考虑其材料参数、强度参数、几何尺寸以及承受载荷等随机因素，用分支限界法识别结构系统的各重要失效序列，应用响应面法对某具体层合板的各失效事件进行计算，进而计算出整个系统的失效概率，并且利用MATLAB程序以及ANSYS中的APDL语言编写了JC法计算程序。计算结果表明，一般情况下层合板首先出现基体损伤失效，然后才会出现纤维断裂失效。这一结果与一些文献中的试验结果相一致，表明这种概率分析方法可以应用于实际复合材料层合板结构的可靠性分析。     

复合导引头多源异步信息融合精确拦截算法

针对单一制导体制难以满足现代战场作战需求且多传感器数据更新率不同步的问题,建立一种新的微惯导/毫米波/红外复合制导体制,研究了该体制下多传感器异步信息融合的时间同步和空间配准问题;提出一种自适应无迹卡尔曼滤波算法,该算法采用预测残差构造状态模型误差统计量,通过自适应因子调整状态模型信息对状态参数估值的贡献,有效控制状态模型噪声异常对状态参数估值的影响。将提出的算法应用到微惯导/毫米波/红外复合制导系统中进行仿真验证,结果表明,提出的自适应无迹卡尔曼滤波算法的解算精度高于标准扩展卡尔曼滤波和无迹卡尔曼滤波算法,能有效提高导弹的制导的解算精度。     

一种新的复合导引头多源异步信息融合精确拦截算法

针对单一制导体制难以满足现代战场作战需求，而多传感器数据更新率不同步的问题，建立一种新的微惯导/毫米波/红外复合制导体制，研究了该体制下多传感器异步信息融合的时间同步和空间配准问题；提出一种自适应Unscented卡尔曼滤波算法，该算法采用预测残差构造状态模型误差统计量，通过自适应因子调整状态模型信息对状态参数估值的贡献，有效控制状态模型噪声异常对状态参数估值的影响。将提出的算法应用到微惯导/毫米波/红外复合制导系统中进行仿真验证，结果表明，提出的自适应Unscented卡尔曼滤波算法的解算精度高于标准扩展卡尔曼滤波和Unscented卡尔曼滤波算法，能有效提高导弹的制导的解算精度。