DLC涂层硬质合金微钻的制备及其切削性能

在硬质合金微型刀具加工高硅铝合金等难加工材料时,通过采用改进的热丝CVD装置开展了DLC涂层硬质合金微钻制备工艺优化,得到了最优沉积工艺,并配合高速加工高硅铝合金(Si15%)材料微小孔钻削性能对比试验,分析了刀具的磨损机理.结果表明:两步预处理方法适合复杂形状硬质合金衬底的预处理方法.钻削高硅铝合金时,DLC涂层具有低摩擦系数和高耐磨损特性,同等切削条件下,涂层微钻的切削寿命比未涂层硬质合金微钻提高了10倍.     

高速钻削复合材料的切削力

采用多种硬质合金钻头,在高转速和不同进给速度条件下对碳纤维/环氧树脂复合材料进行孔加工正交试验,通过研究其轴向力和扭矩以分析刀具条件和切削参数的适应性.结果表明:主轴转速是影响轴向力和扭矩的最主要因素,高转速钻削时轴向力和扭矩都显著减小;减小进给速度也使轴向力和扭矩减小,但其影响小于主轴转速.此外,钻头材质对轴向力和扭矩的影响大于钻头几何形状和进给速度;进给速度对轴向力的影响较大,而钻头几何形状对扭矩的影响较大.     

基于湿热环境下的碳纤维复合材料力学性能研究及老化寿命预测

对T700/TDE-86碳纤维复合材料开展人工加速湿热老化试验,通过对比分析复合材料老化前后剖面形貌和物理化学特性,探讨了复合材料的吸湿扩散行为,研究了复合材料力学性能演变规律;并构建剩余强度计算模型,结合环境系数预测了湿热环境下复合材料的老化寿命。结果表明：复合材料吸湿率随老化时间延长而逐渐增大直至趋于平缓,符合Fick扩散定律;相对于未进行湿热老化的复合材料,经60℃、95%RH湿热环境老化后的复合材料各力学性能均有所下降,其中剪切强度最为严重,老化64 d后其强度下降率高达25%;基于剩余强度与环境系数预估的T700/TDE-86碳纤维复合材料寿命期限约为30年,为树脂基复合材料未来服役可靠性奠定了基础。     

偏置抛物面卫星天线反射器固化变形分析

偏置抛物面卫星天线反射器由碳纤维预浸料铺制而成,在固化过程中通常会出现热变形、固化收缩变形及机械变形等,且过大的变形会导致反射器反射信号产生偏差。为了有效预测天线反射器在热压罐固化过程中的变形,本文采用线性黏弹性本构模型表征纤维增强复合材料在固化过程中的应力-应变关系。采用顺序热-力耦合分析法,对天线反射器内部温度场、固化度场及位移场的分布进行建模,并对铺层结构及降温速率对天线反射器变形的影响开展研究。结果表明：相较于纯0°铺层结构,正交和准各向同性铺层天线反射器z向变形量减小了51%以上,且降低降温速率有助于提高天线反射器的固化型面变形。     

Laser-induced oxidation assisted micro milling of high aspect ratio microgroove on WC-Co cemented carbide

Severe tool wear and poor surface quality are the main problems during micro machining of cemented carbide. In this work, an innovative hybrid process of laser-induced oxidation assisted micro milling (LOMM) was proposed to solve the problems. A nanosecond laser was utilized to induce oxidation of the WC-20%Co material, producing loose oxide which was easy to remove. The micro machinability of the material was improved by laser-induced oxidation. The oxidation mechanisms of cemented carbide were studied. A microgroove with a depth of 2.5 mm and aspect ratio of 5 was fabricated successfully. The milling force, surface quality and tool wear mechanisms were investigated. For comparison, a microgroove was also fabricated with conventional micro milling (COMM) using identical milling parameters. Results revealed that in LOMM the milling force and tool wear rate were extremely low during removing the oxide. The machined surface quality and dimensional accuracy achieved by LOMM were superior to those obtained by COMM. The surface roughness S_a of the microgroove bottom reached 88 nm in LOMM, while the cross-sectional geometry of the microgroove was a trapezoid. Perpendicularity of the microgroove sidewall machined by LOMM was better than that by COMM. The tool wear forms in LOMM were coating spalling and slight tool nose breakage. Compared with COMM, the tool life in LOMM was prolonged significantly. It indicates that the proposed hybrid process is an effective and efficient way to fabricate high aspect ratio micro-features with high dimensional accuracy.     

基于光纤传感的航天器结构应变参数精确测量

为实现空间高低温环境下航天器结构应变参数的精确测量,采用基于法布里–珀罗（Fabry-Perot, F-P）标准具和乙炔（C2H2）气室的复合波长参考的光纤测量方法,对可调谐滤波器透射波长进行校正,以保证解调精度。在解调过程中,采用自适应阈值法解决光源平坦度差引起的F-P标准具寻峰困难问题,并且基于时间预测性最大化原理对透过气室的光源信号进行盲分离,以提高气室波长校正精度。实验结果表明,该方法可实现在高低温环境下光纤传感器中心波长解调偏差小于3 pm,结构应变测量相对误差小于4%,能够满足实际工程应用中航天器结构应变参数的高精度测量需求。     

复合材料不同截面空心柱体压溃吸能特性研究

对圆形截面和正六边形截面碳纤维复合材料空心柱体的压溃吸能特性优劣进行研究。以约束相同质量、相同铺层的方式,分别研究单胞及按蜂窝阵列排列多胞结构2种情况下的吸能特性,并通过 ANSYS 有限元分析及实物试验辅证,得出相同铺层方式不同截面的复合材料空心柱体性能优劣。单胞结构性能结果为,圆截面单胞空心柱体的压溃吸能效果优于正六边形截面的效果:按蜂窝阵列排列多胞结构性能结果为,正六边形截面蜂窝结构压溃吸能能力优于圆截面类蜂窝结构。     

Interconnected Ni（OH）2 and polyether amine on carbon fiber surface for simultaneously improving interfacial adhesion of epoxy composites and electrochemical properties

Interconnected Ni（OH）₂ nanoflakes and polyether amine（PEA） were deposited on carbon fiber tows via a facial and effective process of chemical bath deposition and dip coating. Based on this, a win–win benefit of simultaneously improvements in interfacial shear strength（IFSS） of carbon fiber/epoxy composites and the electrochemical activity has been achieved. Compared with CF and CF-Ni（OH）₂ composites, the IFSS of CF-Ni（OH）₂-PEA/epoxy composite respectively increas...     

玻璃纤维增强酚醛基复合材料平均线胀系数测试影响因素

研究了保温时间、升温速率、预处理温度等对玻璃纤维增强酚醛基复合材料线胀系数测试的影响。结果表明,玻璃纤维增强酚醛基复合材料在加热条件下进一步固化,造成样品收缩与样品受热膨胀相抵消,升温曲线出现平台。因此,测试前应对样品进行预处理,处理温度高于试样最终的测试温度,低于样品固化温度,以免材料内部结构发生变化;设置合适的升温速率,升温速率低,增加了时间成本,升温速率太高,测温热电偶引入的误差增加,且不均匀的加热使试样产生热应力,影响试验结果。     

聚对苯撑苯并双嗯唑（PBO）纤维制备及性能研究

采用4，6-二氨基间苯二酚（DAR）与对苯二甲酸（TPA）缩聚的方法制备PBO聚合物溶液，在180—200℃使聚合物形成液晶态，利用干喷湿纺制法制备纤维。采用DSC、Raman及XRD等方法对纤维进行表征。制备的纤维与商品纤维相比，具有相同的结构和热性能，但表面形貌和强度有差异；两种纤维具有6个相同的主要Raman光谱带，但制备纤维的峰面积较小。制备的PBO纤维热降解温度达650℃，热牵伸处理可使纤维的模量提高至240～300GPa。