聚硅氧硅氮烷胶黏剂耐湿热老化研究

对聚硅氧硅氮烷胶黏剂进行了高温高湿环境条件下的加速老化试验。经过90 d加速老化试验,胶黏剂试样拉剪强度增长了50%以上。在高温高湿条件下,高温对胶黏剂的后固化增强作用和湿度对粘接界面的弱化作用同时存在,但增强作用远大于弱化作用。胶黏剂的90 d加速老化试验结果以及老化机理表明,聚硅氧硅氮烷胶黏剂具有很好的耐高温高湿性能,说明其具有较长的贮存寿命。     

Influence and experiment of cable-net manufacturing errors on surface accuracy of mesh reflector antennas

Cable-net structures are of substantial importance in the construction of large mesh reflector antennas. Owing to the inevitable errors in their manufacturing process, the reflector surface accuracy deteriorates. This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas, and analyze its influence on reflector surface accuracy. Firstly, the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted. Secondly, a non-button connecting method is proposed and analyzed to reduce manufacturing errors. Thirdly, two physical experiment models based on 2.62-meter mesh reflector antenna are made. Finally, numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method. Compared with the traditional method, the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy. Moreover, the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process, and thereby improves the deployment reliability.     

针刺C/C复合材料高温力学性能

文摘采用材料超高温力学性能设备及高温应变测试系统,对针刺C/C复合材料拉伸、压缩性能进行了研究。结果表明:针刺C/C复合材料具有明显的拉、压双模量特性,拉、压模量均随着温度的升高而线性下降,且拉伸模量下降更快;针刺C/C复合材料拉伸、压缩强度均随温度升高而先升高后降低,1 600℃时拉伸强度达到最大值,1 200℃时压缩强度达到最大值;其拉伸破坏为脆性断裂,断口呈现45°豁口;其压缩破坏为典型剪应力引起的压缩失效,破坏面倾角为40°~50°。     

2099 和2196 铝锂合金挤压型材拉伸性能

对4 种不同截面2099-T83 和2196-T8511 铝锂合金挤压型材进行了单向拉伸试验研究,获得了 不同截面、侧壁和厚度型材的应力—应变关系曲线和力学性能。观察铝锂合金的断口形貌发现,各断口分布有 不规则的撕裂带和韧窝,2196-T8511 比2099-T83 铝锂合金断口中的韧窝小且浅,表明2099-T83 铝锂合金塑 性较好,与力学性能测试结果相吻合。     

修复金属板裂纹的复合材料补片正交优化

基于Abaqus软件建立了金属板裂纹复合材料补片修复结构的有限元模型。以应力强度因子(SIF)为判据,利用L9(34)型正交实验考察了各补片参数对修复效果的影响。结果表明:在99%置信度水平下,补片厚度的贡献率为68.77%,铺层顺序的贡献率为29.59%,而补片长度对修复效果的影响不明显。结合工程应用实际与正交分析结果,利用设计好的补片对含中心贯穿裂纹的铝合金板进行了修复,并对修复结构进行了静强度测试。结果表明:修补后静强度为未修复裂纹板的1.32倍,恢复至完好板的97.2%,延伸率为未修复裂纹板的2.24倍,恢复至完好板的50.7%。结论:选用长度为40 mm,厚度为1.2 mm,铺层顺序为[0°/90°]s的正方形补片时修补效果最好。