改善腈纶短纤维卷曲性能的研究

影响腈纶短纤维卷曲性能的主要因素有丝束总线密度 ,卷曲箱高度 ,卷曲压力温度 ,丝束张力 ,宽度及热定型温度。实验证明 ,卷曲轮宽度进丝量为 1.1kdtex/mm较合适 ,卷曲箱高度 8～ 12 mm较好 ,卷曲主压为 0 .2 5 MPa,卷曲温度 75± 1℃ ,丝束张力 0 .5 MPa时 ,可获得较好的卷曲性能。通过调节卷曲前及卷曲中的工艺及设备 ,可提高腈纶短纤维的卷曲性能     

超薄高模量织物研制及其在星载反射器上的应用

为了满足天线反射器轻量化以及高精度要求,通过多级展纱工艺制备超薄碳纤维织物并应用于反射器结构。通过对机械展纱原理进行分析,采用多级展纱辊设备展纱,展纱后纱片宽度为4 mm,织物的面密度为106 g/m2。对展纱后丝束与原丝束进行复丝拉伸试验,实验结果表明,展纱后丝束拉伸强度和模量分别下降了1.26%和1.29%。通过工艺试验制备单层厚度的蒙皮试样,试样表观形貌明显提高。同时结合天线反射器结构,采用有限元仿真手段针对超薄高模量碳纤维织物进行复合材料设计,计算得到天线反射器基频为138.53 Hz,蒙皮减重达到16.1%;将超薄高模量碳纤维织物蒙皮与蜂窝夹芯胶接制造反射器,并通过正弦振动试验验证了超薄高模量碳纤维织物可以应用于星载天线反射器结构。     

Numerical simulation and experimental investigation for design of a carbon fiber tow pneumatic spreading system

The work successfully designs a high efficient carbon fiber pneumatic spreading system. The internal flow field of the fiber pneumatic spreader was first simulated by solving Reynolds-averaged Naiver-Stokes equations, and the characteristics of the flow pattern in the spreader under various operation conditions were analyzed in terms of the mass flow rate and the velocity distributions. Comparisons of numerical results with measured velocity and pressure distributions were made to determine the accuracy of the employed method. A good agreement was found in both qualitative and quantitative analysis. A new variable, spreading evenness, was defined to specify the dispersing extent of fibers in a carbon fiber tow during the fiber pneumatic spreading process. By the spreading evenness, a quantitative comparison of a spread carbon fiber tow can be made and the optimum condition can be easily obtained at fiber spreading experiments. The dispersing mechanism of a carbon fiber tow was comprehensive by the computational modeling and the spreading experiment. The performance of the fiber tow pneumatic spreader system was better than prior studies, and the use of numerical analysis combined with the fiber spreading experiment was useful for the development of the fiber pneumatic spreading system.     

大容量涤纶短纤维卷曲工艺优化

分析了丝束总线密度、丝束张力、卷曲温度以及卷曲压力等工艺,对大容量涤纶短纤维卷曲稳定运行的影响,并对装置增容后的卷曲工艺进行了优化。结果表明:丝束总线密度与卷曲辊的宽度要匹配,卷曲压力要适当。该装置卷曲辊为Φ300 mm×520 mm,卷曲辊间隙0.08～0.10 mm,卷曲温度80～85℃,丝束总线密度5.6×10~6 dtex,卷曲质量好,卷曲机运行稳定。     

基于机器学习的高温后聚丙烯纤维混凝土强度预测

影响高温后聚丙烯纤维混凝土(PFRC)力学性能的因素众多,因此相关试验的周期长,试验量大.如何利用现有试验数据预测高温后聚丙烯纤维混凝土的强度能够有效提高试验效率,为实际工程提供参考.通过研究纤维尺度、纤维掺量和温度对混凝土强度的影响,建立纤维尺度、掺量和温度为因子的回归树(RT)、支持向量机回归(SVR)和BP神经网...     

基于灰色关联分析的极限学习机在混凝土抗压强度预测分析中的应用*

利用灰色关联分析法筛选出表征混凝土抗压强度的重要因素指标,并以选取的因素指标为输入变量、以抗压强度为输出变量,创建极限学习机(ELM)模型,克服了冗余因素对模型精度的影响。实例分析表明经指标优化选择的ELM模型具有较高的精度,对抗压强度的预测效果明显优于未经指标筛选的ELM模型,也远好于支持向量机的预测效果,为混凝土抗压强度预测提供了一种新思路。     

超声辅助纤维束展纱效果研究

针对卫星轨道飞行器铺丝用预浸纱要求,开展热熔法制备展纱工艺研究。对比分析超声池和超声杆两种超声辅助方法对浸胶前纤维束展开宽度的影响,研究超声波辅助展纱机理,并结合展纱辊展纱,研究不同展纱方式对纤维束展开宽度及损伤的影响。研究结果表明:由于超声池宽度回缩效应,超声杆法优于超声池法;与展纱辊展纱相比,超声展纱展开宽度增加了18.2%,纤维损伤强度减少了4.03%;两种展纱方式相结合宽度增加至1.66倍,纤维拉伸强度降低至89.14%,两种展纱方式相结合可以提高展纱效率。     

对当前碳纤维供不应求的一些看法

简述了2005年以来世界碳纤维市场出现供不应求和价格大幅上涨的局面。分析了世界碳纤维的生产能力、需求增长情况和造成供不应求的原因。指出造成当前国内碳纤维价格非正常上涨的原因,是在全球碳纤维市场供不应求的基础上人为哄抬的结果,相信碳纤维价格在不久将会回落;先进的分丝技术使12k和24k等较大丝束取代3k、6k甚至1k等小丝束碳纤维来制备先进复合材料的技术可行,在航空、航天等高技术领域得到应用。     

Effect of Fiber Drawing Tension on Optical and Mechanical Properties of Optical Fiber Waveguides

Based on experimental results, the effects of fiber drawing tension on both optical and mechanical properties of optical fibers are discussed. Lower drawing tensions (i.e. > 0.05 N (5 g)) were found to be desirable for fabricating uniform high-strength fibers, whereas higher drawing tensions (i.e. > 0.5 N (50 g)) were better for low-loss fibers having a large silica core.     

纤维缠绕圆筒复合材料固化成型过程机理模型（中）

本文介绍了Springer的一个关于圆筒复合材料纤维缠绕过程的模型。该模型将重要的过程变量如：缠绕速率、纤维张力,操作温度与复合材料筒体和心轴的热化学和力学行为关联起来。以模型为基础编制的程序可以用来计算：1）筒体和心轴内的温度分布。2）筒体内的固化度和粘度的分布。3）纤维的张力和纤维的位移分布。4）筒体和心轴内的应力和应变。5）筒体内的应力和应变分布。     

Dehydrogenation kinetic model of heavy paraffins

Based on the dehydrogenation mechanism of heavy paraffins under industrial conditions, the intrinsic reaction kinetic model and catalyst deactivation model were established considering the influence of side reactions with different carbon‐number heavy paraffins. Based on the experimental data of dehydrogenation reactions with different carbon‐number paraffins in an axial continuous‐flow isothermal fixed‐bed microreactor, Powell optimization method was used to estimate the model parameters. The results show that there is a liner relationship between the activation energies and pre‐exponential factors of homologous reactions and carbon number of paraffins. A correlation model about the deactivation rate constants under different conditions was established. The validation of kinetic model showed that the model could be used to predict detailed product distribution with different feedstocks under different reaction conditions. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

混合流体汽液及液液界面张力分子模型

应用定标粒子理论表面张力方程以及 vd W- 1型混合规则 ,计算了混合流体的表面张力 ,对 64个二元体系 ,7个三元体系的表面张力计算平均相对偏差为 0 .80 %和 2 .43% ;应用 Boudh- Hir和 Mansoori提出的部分互溶体系的界面张力模型 ,给出了硬球直径的确定方法 ,对 37个部分互溶二元含水体系的界面张力进行了计算 ,绝对平均偏差为 1 .5m N/m,相对平均偏差为 8.9% ,计算精度满意。     

Multi-scale modelling of progressive damage and failure behaviour of 2D woven SiC/SiC composites

In this paper, a multi-scale modelling approach has been developed to predict the progressive damage and failure behaviour of 2D woven SiC/SiC composites. At the tow scale, non-linear tow properties have been determined by a micromechanics-based damage model, in which two scalar damage variables were introduced to characterize the fibre-dominated and matrix-dominated damage, respectively. Based on periodic boundary conditions, a meso-scale unit cell model has been established to simulate the macroscopic stress-strain responses and progressive damage processes of the composite under uniaxial tensile, compressive and in-plane shear loadings, respectively. In the numerical method, the non-linear properties of constituent materials have been implemented by the user defined subroutine, USDFLD of the finite element package, Abaqus. The numerical results and their comparisons with experimental stress-strain curves have been presented. The failure mechanisms of the composite under each loading have been also discussed. The high efficiency and prediction accuracy of the model make it possible to analyse large scale woven composites.     

涤纶短纤维牵伸机传动齿轮强度的验算

计算了15kt/a涤纶短纤维第三牵伸机(DF_3)前13只辊筒在不同负荷,不同情形下丝束的张力,根据丝束张力计算输入、过桥及前5只辊筒传动齿轮节圆上的圆周力。根据日本齿轮协会标准计算出许用圆周力,得出安全系数,为涤纶短纤维纺丝线增容20％提供理论依据。     

薄壁钢内衬CF圆筒承压性能仿真及水压爆破试验

针对含薄壁钢内衬的碳纤维缠绕圆筒典型结构,建立三维有限元模型,采用温度参数法逐层计算内衬剩余应力,并预测其承压性能;基于水压爆破试验,研究了多缠绕角下缠绕张力、不同碳纤维等级对钢内衬及复合材料圆筒承压能力的影响,并结合钢内衬的声发射振铃计数特征判别载荷屈服点。试验结果表明,含薄壁钢内衬的碳纤维缠绕圆筒的最佳缠绕张力为75 N左右,T700,T300两种强度碳纤维复合圆管的钢内衬最大屈服载荷基本相同。     

激光与微波协同加热碳纤维的温度与热应力分布规律

利用仿真软件建立微波加热-激光加热-热辐射-流动传热-固体力学多物理场模型，研究了激光加热直径1mm碳纤维丝束的温度场分布与热应力大小，以及不同激光功率对于温度场与热应力的影响。同时，首次提出激光加热与微波加热结合的方式调节温度场分布与热应力大小的方法，仿真结果显示激光加热与微波加热结合的方式可以改善碳纤维丝束温度场的分布，有效降低丝束加热过程中的热应力。     

玄武岩复合材料筋增强ECC受拉性能及裂缝控制机理

工程水泥基复合材料(ECC)因其高韧性和多缝开裂特性成为研究热点,纤维复合材料(FRP)因具有抗拉强度高、密度小、耐腐蚀性好等优点而受到广泛关注。为研究玄武岩复合材料(BFRP)筋增强ECC(BFRP-ECC)的受拉性能以及筋材对基体的裂缝控制机理,考虑了基体类别和配筋率等因素,对ECC狗骨试件、BFRP-ECC和BFRP-砂浆薄板试件进行了单轴拉伸试验,同时借助数字图像相关法(DIC)技术获得了试件受拉过程中的全场应变和开裂状态,基于Richard的弹塑性应力应变公式提出了BFRP-ECC单轴受拉应力应变本构模型。结果表明：BFRP-ECC的极限拉应力随配筋率的增加而增大;ECC基体对复合材料的受拉性能增强效果优于砂浆基体,同时以ECC为基体的复合材料在裂缝间距和宽度控制上都明显优于以砂浆为基体的复合材料;BFRP筋能增加BFRP-ECC裂缝处的桥连应力,减小裂缝间距和宽度,增加裂缝数量。本文建立的BFRP-ECC单轴受拉应力应变本构模型与试验数据吻合良好,较好地反映了BFRP-ECC受拉应力应变关系。     

The gap between the measured and calculated liquid–liquid interfacial tensions derived from contact angles

We present our new findings about the causes of discrepancies between the measured and calculated liquid-liquid interfacial tensions derived from contact angles. The calculated ones are based on either the equation developed by Fowkes or that by van Oss, Chaudhury and Good (VCG), while the measured ones are based on the sessile drop, weight-volume by Jańzuk et al. and the axisymmetric drop shape analysis (ADSA) by Kwok and Neumann. Indeed, there are deviations between the calculated and measured results. For an immiscible liquid-liquid or liquid-solid interface, we prefer to employ Harkins spreading model, which requires the interfacial tension to be constant. However, for the initially immiscible liquid-liquid pairs, we propose an adsorption model, and our model requires the interfacial tension to be varying and the surface tensions of bulk liquids at a distance from the interface to remain unchanged. Thus, the difference between the initial and final interfacial spreading coefficients (S_i) equals the equilibrium interfacial film pressure (π_i)_e. According to our findings, the calculated interfacial tension represents the initial value (γ₁₂)_o, which differs from the equilibrium value (γ₁₂)_e obtained experimentally after some time delay. This expected gap at a reasonable time frame is chiefly caused by the equilibrium interfacial film pressure between the two liquids. The initial (or calculated) interfacial tension can be positive or negative, while the equilibrium (or measured) one can reach zero. In fact, the former is shown to have more predictive value than the latter. A negative initial interfacial tension is described to favor miscibility or spontaneous emulsification but it tends to revert to zero instantaneously. Thus, a miscible liquid mixture should have zero interfacial tension. In response to recent papers by Kwok et al., we show that the disagreements between the calculated and measured interfacial tensions are definitely not caused by the failure of the VCG approach. Correct interfacial tensions are calculated for liquid pairs containing formamide or dimethyl sulfoxide (DMSO) by using the dispersion components cited in Fowkes et al.'s later publication. With the corrected surface tension components, the equilibrium interfacial film pressures (π_i)_e's for at least 34 initially immiscible liquid pairs have been calculated. These values are generally lower than the corresponding spreading pressures π_e's obtained by others using the Harkins model. Recently, we established a relationship between these two film pressures with the Laplace equation and found a new criterion for miscibility to be (π_i)_e = π_e.     

上海地区高等级公路沥青路面使用性能预测方法研究探讨

在分析评价现有路面使用性能预测模型的基础上,分别采用马尔可夫概率预测模型和灰色理论预测模型,针对上海及类似地区高等级公路沥青路面进行使用性能预测分析。实例结果表明,马尔可夫概率预测模型受养护水平与PC I频数的干扰较大而适用性不强,而灰色理论预测模型具有受测试数据样本量影响小、预测精度高及适用性强等优点,因此更能适应上海及类似地区高等级公路沥青路面使用性能的预测,对公路养护决策具有重要意义。     

端钩型钢纤维UHPC抗压强度的试验研究

本文对5组超高性能混凝土(UHPC)立方体试件进行了轴心受压试验,观察不同纤维掺量及不同尺寸UHPC试件的破坏过程及破坏形态,研究了端钩型钢纤维及不同尺寸对UHPC受压性能的影响,比较各纤维体积掺量立方体试块的荷载-位移曲线,给出了纤维约束系数,分析了其对UHPC立方体抗压强度及压缩耗能的影响,建立了UHPC立方体抗压强度的预测模型。结果表明:与未掺纤维UHPC试件相比,掺入端钩型钢纤维的试件,在载荷达到极限荷载的40%左右时,试件开始发生损伤,在载荷接近极限荷载时,试件内部发生持续的快速断裂声响;掺入端钩型钢纤维的UHPC试件最终破坏呈多条斜向裂缝,且最终破坏时试件仍能保持完整形态,呈现“裂而不碎”的状态;随着端钩型钢纤维体积掺量的增加,试件的受压峰值荷载增加,且伴随着试件的变形增大;与未掺纤维UHPC试件相比,随着纤维掺量的增大,尺寸效应对UHPC的受压性能的影响逐渐减小。基于纤维约束指数,建立了UHPC立方体抗压强度的预测模型,预测结果与试验结果吻合度较高。