自动铺丝末端缺陷角度对层合板拉伸性能的影响

自动纤维铺放(AFP)工艺能够有效制造大型复合材料构件,但在铺放过程中因为丝束末端等断面而出现不同角度内嵌缺陷。为解决相关问题,按照[(90°/0°)5/90°]和[(0°/90°)5/0°]的铺层顺序,在0°和90°铺层内分别设置不同丝束末端角度的孔隙缺陷或重叠缺陷。结果表明:不同角度纤维铺层内嵌不同角度缺陷时,导致复合材料构件差异明显。在90°纤维铺层方向上,内嵌90°孔隙缺陷和90°重叠缺陷时,试件拉伸强度最高,拉伸强度比分别为90. 89%和90. 11%。在0°纤维铺层方向上,内嵌±30°孔隙缺陷和30°重叠缺陷时,试件拉伸强度最高,拉伸强度比分别为28. 48%和50. 71%。     

Effects of FDM-3D printing parameters on mechanical properties and microstructure of CF/PEEK and GF/PEEK

Fused deposition modeling (FDM) has unique advantages in the rapid prototyping of thermoplastics which have been developed in diverse fields. However, although great efforts have been made to optimize FDM process, the mechanical properties of printed parts are limited by the weak interlamination bonding as well as the poor performance of raw filaments used, such as acrylonitrile butadiene styrene (ABS), polylactic acid (PLA). Adding fibers into thermoplastic matrix and preparing high-performance filaments have been indicated to enhance the properties of fabricated parts. Recently, heat-resistant polyetheretherketone (PEEK) and its fiber reinforced composites were proposed for FDM process due to overcoming the limitation of equipment and process. However, few researches have been reported on the effects of FDM-3D printing parameters on the mechanical properties of fiber reinforced PEEK composites. Therefore, 5wt% carbon fiber (CF) and glass fiber (GF) reinforced PEEK composite filaments were prepared respectively in this study. The effects of various printing parameters including nozzle temperature, platform temperature, printing speed and layer thickness on the mechanical properties (including tensile strength, flexural strength and impact strength) were surveyed. To analyze the microstructure and failure reasons of printed CF/PEEK and GF/PEEK samples, the tensile fractured surfaces were investigated via scanning electron microscope (SEM).     

2219 铝合金双轴肩搅拌摩擦焊接头组织与性能分析

对2219铝合金进行了双轴肩搅拌摩擦焊工艺试验,详细分析了焊缝成型、接头组织形态及力学性能.结果表明:2219铝合金双轴肩搅拌摩擦焊缝正反面成型美观,内部无缺陷,几乎无焊缝减薄.接头宏观形貌呈典型的“哑铃型”,焊缝上下表面宽,中间略窄.从显微组织角度看,接头的焊核区、热机影响区、热影响区等组织特征与常规搅拌摩擦焊相似.双轴肩搅拌摩擦焊接头显微硬度分布趋势与常规搅拌摩擦焊接头相似,均为典型的“W”型,但双轴肩搅拌摩擦焊接头不存在各层异性.接头力学性能试验表明:双轴肩搅拌摩擦焊接头抗拉强度达到了318.3 MPa,延伸率为5.5％.接头断口形貌呈典型的韧性断裂.     

溶胶-凝胶法制备SiO2 -TiO2 / 聚酰亚胺杂化材料及其性能

采用溶胶-凝胶法制备了纳米SiO2-TiO2溶胶,然后通过共混法制得SiO2-TiO2/聚酰亚胺杂化材料,SEM、DMTA和TGA等方法研究了无机组分的含量对聚酰亚胺性能的影响。结果表明:SiO2-TiO2/聚酰亚胺杂化材料的冲击强度和弯曲强度随无机粒子含量变化而变化,当无机粒子含量为3%(质量分数)时二者出现最大值,其冲击强度较纯树脂提高了177%,弯曲强度提高了54.6%。另外,随着SiO2-TiO2无机材料的增加,杂化材料热稳定性亦有所提高。     

高强耐热镁合金陀螺仪支架精密锻造工艺

采用数值模拟的方法研究了高强耐热镁合金陀螺仪支架的等温锻造过程,分析了坯料形状、锻造方案对构件成形过程中金属流动行为的影响,根据模拟的结果制定了相应的成形方案,并成功锻造出了高强耐热镁合金陀螺仪支架锻件.对该锻件进行了时效热处理工艺研究,得出优化的时效处理制度为200℃ ×63 h.在该时效制度下,材料的室温抗拉强度达到了371MPa,屈服强度达到243MPa,伸长率达4.1％     

NEPE高能推进剂力学性能模拟计算

将颗粒填充聚合物三相结构(颗粒相-中间相-基体相)和粘弹模型相结合,提出了NEPE高能固体推进剂三相结构粘弹模型,建立了NEPE高能推进剂力学性能与其配方组成、固体填料粒径及级配、弹性母体(基体)的拉伸强度和模量、界面层模量等参数的数学关系,进行了编程计算,其拉伸强度和伸长率90%的计算值和测试结果相对误差小于20%。     

陶瓷隔热瓦力学性能影响因素及其稳定性控制

通过研究陶瓷隔热瓦力学性能与密度之间的变化关系,发现陶瓷隔热瓦的密度均匀性是影响其力学性能稳定性的重要因素.通过工艺改进制备了力学性能稳定的陶瓷隔热瓦,陶瓷隔热瓦的平均拉伸强度由0.250 MPa提高到0.786 MPa.结果表明:提高陶瓷隔热瓦的密度均匀性是控制其力学性能稳定性的有效途径.     

高增塑聚乙二醇聚氨酯弹性体形态结构的研究

研究了高增塑聚乙二醇聚氨酯弹性体网络的形态结构,结果表明,由于极性增塑剂的存在,室温条件下,体系不存在结晶;常温条件下,不同增塑剂含量的聚乙二醇聚氨酯弹性体网络均不存在微相分离形态结构。     

增塑剂及燃烧催化剂对BAMO-THF复合推进剂性能的影响

采用混合硝酸酯(NG+DEGDN)和2,2-二硝基丙醇缩甲醛与2,2-二硝基丙醇缩乙醛混合物(A3)研究了增塑剂对3,3-二叠氮甲基氧丁环-四氮呋喃共聚醚(BAMO-THF)复合推进剂燃速、力学性能的影响。结果表明NG+DEGDN增塑的推进剂燃速和力学性能均优于A3。另外,研究了一种有机过渡金属燃速催化剂(代号OME)对BAMO-THF复合推进剂性能的影响。在显著提高BAMO-THF复合推进剂燃速同时,OME还可提高该体系力学性能。X射线光电子能谱(XPS)分析表明OME与粘结剂中叠氮基团存在作用力。     

Microstructure evolution and mechanical anisotropy of M50 steel ball bearing rings during multi-stage hot forging

This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging (MSHF) and subsequent spheroidizing annealing (MSHFA). To this end, the present study mainly employed stereo microscopy, Optical Metallurgical Microscopy (OMM), Scanning Electron Microscopy (SEM), and Electron Backscatter Diffraction (EBSD) to characterize and analyze the workpiece at each processing stage of MSHF while performing microhardness measurement and uniaxial tensile experiment to test and analyze the mechanical properties of the workpiece. Macro-structure observation showed that the simulation results of flow lines at each stage were consistent with the experimental results. Microscopic observation showed that, after MSHF, deformation gradually became less significant along the outward radial direction of the bearing ring. After MSHFA, the microstructures of the bearing ring became uniform, whereas primary carbides did not dissolve. The mechanical properties were better in the axial direction (AD) than in the radial (RD) and circumferential directions (CD) after MSHF due to the smaller grain width. After MSHFA, the mechanical properties in the ADs and CDs were better than those in the RDs, which was due to the large cross-sectional area of carbides along the flow-line direction.