工业机器人在立体编织物中的应用——小间距铺设纤维的方法及装置

针对立体编织预制体铺纱成型工艺在科研和生产中均是人工实施铺纱的现状,提出了应用六轴工业机器人铺设小间距纤维方法及装置的解决方案。实现立体编织预制体生产的自动化和柔性化,解决人工铺设纤维生产周期长、出错率高、纤维纱线张力不均匀、质量不稳定的问题。     

机器人视觉系统在立体编织自动铺纱过程中的应用研究

文章着重讨论了视觉系统应用于立体编织小间距自动铺纱路径规划及实施方案。提出了机器人视觉系统在立体编织自动铺纱过程中的应用方案;解决了机器人连续铺纱的技术难题;机器人具有的灵活性、智能性和环境适应能力的特点在立体织物铺纱成型工艺中得到了更好的应用。     

编织结构复合材料RTM成型流场仿真模拟

针对航空发动机用编织结构复合材料树脂传递模塑料(RTM)成型工艺,开展了增韧树脂基体的工艺特性及编织结构预制体的渗透特性研究,并结合PAM–RTM软件对RTM成型工艺方案进行了研究,研究结果表明,1304增韧环氧树脂RTM成型的工艺窗口期仅有25 min,8步法编织结构经向渗透率远大于纬向和Z向渗透率。通过PAM–RTM软件对RTM成型树脂注射流道和工艺参数进行设计,获得了航空发动机用高韧性编织结构复合材料RTM成型工艺方法。     

多墙结构副翼RTM整体成型工艺研究

采用树脂转移模塑成型(RTM)工艺，研究多墙结构副翼低成本整体成型的可行性。采用数值模拟技术对多墙结构副翼的树脂流动过程进行了模拟计算，根据模拟结果选择合理的注射方式和工艺参数，同时采用碳纤维编织套管成型副翼墙，以进一步降低制造成本。对所选方案进行了工艺试验验证，并对结构件进行了质量检测。结果表明：碳纤维编织套管的应用大大提高了预制体的制备效率，节省人工约60%；理论充模时间和试验充模时间基本一致；结构件表观质量良好，厚度分布均匀，内部无缺陷，验证了所选模拟方案合理有效，整体成型方案切实可行。研究结果为低成本制造高性能复合材料多墙结构件提供了参考。     

一种航空发动机涡轮叶盘预制体工艺设计方法

概述了当前涡轮叶盘预制体的结构类型，得出2D叠层极性编织结构具有力学性能优良和成型难度低的优势。预制体的结构设计对复合材料的性能有显著影响，当前涡轮叶盘预制体研究的相关文献还很少，尤其是体积分数设计方面。为此，提出了一种极性编织结构涡轮叶盘预制体的结构设计方法，推导出能满足体积分数设计要求的结构参数关系式，并通过一个实例对该关系式进行说明验证。研究表明：该种航空发动机涡轮叶盘预制体的工艺设计方法具有实用性。     

其他

<正>复合材料预成型体自动编织装备等两项目通过鉴定近日,受中国纺织工业联合会委托,中国纺织机械协会在江苏徐州召开了东华大学和徐州恒辉编织机械有限公司联合承担的中国纺织工业联合会科技指导性项目"复合材料预成型体自动编织装备"和"特种编织技术与装备及其产业化"成果鉴定会。复合材料预成型体自动编织装备项目建立了编织机主传动系统动力学模型、纱线摩擦力模型,获得了编织机的运     

法向增强预制体/酚醛扩张段RTM制备技术研究

RTM工艺可实现扩张段构件近净尺寸成型,纤维体积含量可达53. 1%～59. 9%。本文对法向增强预制体/酚醛扩张段RTM制备技术涉及的树脂基体、法向增强预制体、注射设备与模具进行了讨论。采用RTM工艺制备以酚醛树脂为基体,以2. 5 D编织预制体或针刺预制体为增强材料的扩张段材料并分析其性能,研究结果表明,扩张段构件的层间剪切强度高达59. 2 MPa以上,抗烧蚀冲刷性能显著提高。     

石英纤维准三维结构针刺预制体性能分析

本文研究了预制体内部结构对石英纤维准三维针刺预制体力学性能的影响,力学性能包括:X-Y向拉伸强度、Z向连接强度、T型剥离强度.研究表明:全网毡针刺结构、单层织物/网毡针刺结构、双层织物/网毡针刺结构预制体X-Y向拉伸强度递增;含织物预制体Z向连接强度和T型剥离强度递减.针刺成型工艺过程中短纤维迁移是Z向性能提高的关键.合理设计针刺预制体内部结构,可优化石英纤维针刺预制体X-Y向和Z向的各项性能.     

干铺丝预制体的液体成型工艺研究

为解决RTM类成型工艺中的预制体制备及定型问题,在国内率先开展对干铺丝-液体成型工艺的研究,主要研究内容为液体成型过程工艺参数影响机制及制件的力学性能。采用单因素法确定液体成型时预制体粘结剂含量、注胶温度、充模时间的影响机制,再通过正交法确定了最佳工艺组合,最后就层间剪切与弯曲性能与模压工艺进行比较。实验结果表明,液体成型过程中,树脂的流动充模会受到工艺参数不同程度的影响,注胶温度的影响最大,充模时间影响甚微,通过正确的工艺组合可以减少孔隙等缺陷,保证复合材料的内部质量。力学性能测试表明,干铺丝-液体成型工艺的力学性能水准与模压工艺持平,其中弯曲强度略有降低。     

先进拉挤技术辅助成型等截面螺旋结构制品的研究

为了提高等截面螺旋结构制品的成型效率及自动化程度,对其成型工艺进行了研究。针对该结构制品的截面尺寸及其预制体的工艺特征,进行了成型参数设计和工艺试验,最终采用先进拉挤工艺(ADP)制备了等截面的预制体,并将预制体扭转填充至螺旋槽中真空固化成型了相关制品。研究表明,采用ADP辅助成型等截面螺旋结构制品的自动化程度高、致密性好,制品表观质量有所改进。     

三维机织热塑性复合材料新工艺的开发

为了解决三维机织热塑性复合材料中三维机织预型件的织造和热塑性基体浸入预型件这两大难题,开发了制备三维机织热塑性复合材料的新工艺,即微编纱的编织-用微编纱织造三维机织预型件-复合固化成型.该工艺的创新点是利用微编纱来织造三维机织预型件,然后复合成型.对微编纱的性能做了基本的介绍,主要探讨了三维机织预型件的织造及复合成型工艺,为日后三维机织热塑性复合材料的生产加工开辟了一条新的途径.     

不同填充率下FDM 3D打印预制件建模及力学性能分析

以拉伸、压缩、弯曲、扭转4种受载情况下的熔融沉积型三维（FDM 3D）打印预制件为研究对象，以填充率、填充单元结构类型为分析参数，通过确定3D打印预制件填充率的影响因素，建立了填充率与格子形填充单元几何参数的通用解析式，据此构建不同填充率下3D打印预制件的三维几何模型；然后对不同受载类型3D打印预制件进行有限元仿真分析，明确填充率对不同载荷工况下3D打印预制件力学特性的影响规律。仿真和实验结果表明，填充率对3D打印预制件所受拉伸应力、压缩应力、弯曲应力均有较大影响，而扭转情况下影响较小，据此进一步确定了一定受载情况下3D打印预制件的较优填充率；基于本文提出的不同填充率下预制件三维模型建立方法，可有效实现对预制件的力学性能仿真分析，对减少产品试验验证次数、降低研发成本具有积极作用。     

任意矩形组合截面二步法三维编织的纱线布置规律及其计算机辅助设计

本文研究了任意矩形组合截面二步法三维编织的纱线布置规律。并利用软件使二步法三维编织的工艺设计安全由计算机实现，为二步法三维编织的安全自动化奠定了软件基础。     

Surfactant effect on DLP fabrication of silica fibre preforms

Three-dimensional (3D) printing based on digital light processing (DLP), for its great advantage in dealing with material and structural complexities, is being engaged for the fabrication of custom-designed silica optical fibre preforms. Resin preparation and printing are key processes critical to DLP fabrication of optical fibre preforms with high silica loading. In this work, the surfactant effect on preparation of resin and DLP printing of optical fibre preforms for higher silica loading is investigated. Based on our experimental studies of the rheological and photocuring properties of resins and the quality of printed silica fibre preforms, we find that, in the case where 2-phenoxyethanol (POE) is usually added as the surfactant, the resin has higher viscosity and results in poorer preform quality. By removing POE from resin ingredients and designing a multi-step resin processing with appropriate settling and degassing processes, fibre preforms with high silica loading up to 0.8 (w/w) have been successfully fabricated.     

Hysteresis loops of carbon fiber-reinforced ceramic-matrix composites with different fiber preforms

The hysteresis loops of C/SiC ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply, 2D and 2.5D woven, 3D braided, and 3D needled at room temperature have been investigated. Based on fiber slipping mechanisms, the hysteresis loops models considering different interface slip cases have been developed. The effects of fiber volume fraction, matrix cracking density, interface shear stress, interface debonded energy, and fibers failure on hysteresis loops, hysteresis dissipated energy, hysteresis width, and hysteresis modulus have been analyzed. An effective coefficient of fiber volume fraction along the loading direction (ECFL) was introduced to describe fiber preforms. The hysteresis loops, hysteresis dissipated energy and hysteresis modulus of unidirectional, cross-ply, 2D and 2.5D woven, 3D braided and 3D needled C/SiC composites have been predicted.     

预制体孔隙结构对炭/炭复合材料ICVI制备工艺的影响

研究了预制体孔隙结构对ICVI工艺致密化过程及基体热解炭微观结构的影响。结果表明：2D针刺炭毡致密化速度高于炭布叠层预制体，1K炭布叠层预制体的致密化速度高于3K炭布叠层；在致密化过程中，热解炭均匀沉积在纤维表面，预制体AS／VR比值变化是导致热解炭微观结构发生改变的根本原因。     

Chemical vapor infiltration of additively manufactured preforms: Pore-resolved simulations and experimental validation

The densification of additively manufactured porous preforms by chemical vapor infiltration (CVI) is studied using pore-resolved simulations and experiments. Experimentally, 3D printed silicon carbide (SiC) preforms are subject to CVI synthesis using methyltrichlorosilane (MTS) precursor to obtain high purity SiC/SiC composites. Optical images of the cross sections of the processed preforms are analyzed to obtain the spatial porosity distribution. The numerical method is based on a level set formulation to capture the spatial distribution and time evolution of the pore scale microstructural characteristics. The coupled transport and kinetic effects are represented using a dimensionless Thiele modulus. Simulations are initialized using representative synthetic preform geometries comprising of packed particles based on the size distribution of the powder used for 3D printing. The simulation results are validated against the experimental observations in terms of total density and the distribution of residual porosity. The densification characteristics, porosity classification, concentration profiles, and structure functions are analyzed as functions of processing temperature and Thiele modulus.     

Effects of air oxidation on mesophase pitch-based carbon/carbon composites

Mesophase pitch-based carbon–carbon (C/C) composites were fabricated by cycles of impregnation/carbonization using two different preforms. Air oxidation was used as a stabilization process prior to carbonization. In order to study the effects of air oxidation, composites without air oxidation were also fabricated for comparison. The results showed that the effect of air oxidation was different for different preforms. For 2-dimensional (2D) punched carbon cloth preforms, air oxidation could greatly shorten the fabrication period, and had significant effects on the matrix microstructures. Without air oxidation, the carbon matrix of the composites consisted of small domains with a mosaic texture. With air oxidation, the matrix consisted of domains mingled with flow domains. However, air oxidation had little effect on composites prepared from 2D carbon felts preforms, and the corresponding carbon matrix in the composites consisted of mainly small domains with a mosaic texture irrespective of air oxidation.     

Fabrication and characterization of carbon fiber reinforced SiC ceramic matrix composites based on 3D printing technology

A novel method has been developed to fabricate carbon fiber reinforced SiC (C_f/SiC) composites by combining 3D printing and liquid silicon infiltration process. Green parts are firstly fabricated through 3D printing from a starting phenolic resin coated carbon fiber composite powder; then the green parts are subjected to vacuum resin infiltration and pyrolysis successively to generate carbon fiber/carbon (C_f/C) preforms; finally, the C_f/C preforms are infiltrated with liquid silicon to obtain C_f/SiC composites. The 3D printing processing parameters show significant effects on the physical properties of the green parts and also the resultant C_f/C preforms, consequently greatly affecting the microstructures and mechanical performances of the final C_f/SiC composites. The overall linear shrinkage of the C_f/SiC composites is less than 3%, and the maximum density, flexural strength and fracture toughness are 2.83?±?0.03?g/cm³, 249?±?17.0?MPa and 3.48?±?0.24?MPa m^1/2, respectively. It demonstrates the capability of making near net-shape C_f/SiC composite parts with complex structures.     

Comparison of the mechanical hysteresis of carbon/ceramic-matrix composites with different fiber preforms

The mechanical hysteresis of four ceramic matrix composites with different carbon fiber preforms, i.e. needled C/SiC, 2D C/SiC, 2.5D C/SiC, and 3D C/SiC, was investigated and compared during cyclic reloading-unloading tests. An effective coefficient of the fiber volume fraction in the direction of loading (ECFL) was defined to characterize fiber architectures of the preforms. It is shown that an increase in permanent strain and a decrease in stiffness with the applied stress were strongly affected by the ECFL. The thermal residual stress (TRS) and ultimate tensile strength of the composites are predicted theoretically related to the ECFL, and then validated by experimental results and microstructural observations. The predicted results not only demonstrate good agreement with experimental measurements, but also explain why differences in the composite ECFL result in substantial variations in TRS.