Longitudinal permeability determination of dual-scale fibrous materials

In this work, the longitudinal permeability of squarely packed dual-scale fiber preforms is studied theoretically. These fiber preforms are composed of aligned porous tows and the tows are tightly packed. The effective permeability is calculated as a parallel-like network of intra-tow permeability and inter-tow permeability, which are quantified by Darcy’s law and the inscribed radius between tows, respectively. The jump velocity at the interface between inter-tow fluids and porous tows is considered, as derived by substituting Beavers and Joseph’s correlation into Brinkman’s equation. We further examine the effects of intra-tow permeability on the effective permeability of the fibrous system with three interface conditions: (1) interface velocity = 0, (2) interface velocity = mean intra-tow velocity, and (3) interface velocity = jump velocity. The jump-velocity-based model is found to be closest to numerical data. The influence of the fiber volume fraction of tows on the effective permeability is also analyzed.     

钡酚醛树脂体系化学流变特性研究

在粘度实验和DSC热分析实验的基础上,对用于RTM工艺的钡酚醛树脂体系的化学流变特性进行研究,并根据双阿累尼乌斯方程建立树脂体系的流变模型。模型与实验结果具有良好的一致性。模型可揭示树脂体系在不同工艺条件下的粘度变化规律,定量预报RTM工艺树脂的低粘度平台工艺窗口,为合理制定RTM工艺参数、保证产品质量和实现工艺参数的全局优化提供必要的科学依据。     

超声处理对RTM成型复合材料界面性能的影响

在RTM成型过程中采用超声技术。探讨了超声处理的最佳工艺参数,着重研究超声处理对RTM成型复合材料界面性能的影响。结果表明,在RTM成型过程中采用超声技术增加了树脂对纤维增强体的浸润性,使树脂中的空气和成型过程中产生的气泡易于排出,从而减少了复合材料的孔隙率,进而改善复合材料的界面性能。     

树脂传递模塑工艺中工艺参数对树脂-纤维界面的影响

本文系统研究了工艺参数对由树脂传递模塑成型的复合材料的拉伸强度和树脂-纤维界面的影响.这些参数包括注射压力和模腔/纤维毡的温度.在较低的注射压力和较高的成型温度下,纤维得到良好的浸润和粘结,成型复合材料的拉伸强度也较高.     

酚醛树脂及其复合材料成型工艺的研究进展

随着社会的发展,人们越来越重视安全和环保。新型酚醛树脂品种和酚醛树脂新的成型工艺得到了发展。文中介绍了酚醛树脂的改性方法。重点介绍了基于酚醛树脂的RTM、拉挤等复合材料成型工艺研究进展。     

RTM制品常见缺陷及其对策

本文主要阐述了RTM制品缺陷产生的原因及其解决方法.     

RTM二维径向流动模型的理论概况及研究

综述了牛顿流体在放置了各向同性和各向异性预制件的RTM平板模具中二维径向恒流和恒压渗流的流动模型.对各个模型的可测量物理量之间的关系通过求解其解析解进行了必要的拓展补充推导和研究分析,对传统的二维解析方程进行了拓展和改进,提供了在不透明模具中测定渗透率的方法.即在恒流条件下利用压力传感器和恒流泵测定预制件的二维渗透率;或者在恒压条件下利用数字流量计和压力表测得二维渗透率.这些解析解的关系式也可用于实验预估模具中的压力分布及充模时间等.     

RTM汽车部件工业化生产技术研究

针对RTM汽车制品工业化生产急需解决的生产效率和产品质量稳定性问题,对制造工艺、质量控制体系以及生产装备等方面进行了系统研究.通过对引发体系类型、各组分用量以及温度调整,确定了适宜生产的固化体系;通过研究复合材料模具结构及其制造工艺,提高了模具的表面质量、型腔尺寸稳定性;通过对各生产环节的集成,建立了工业化生产线.     

A fuzzy reasoning and fuzzy-analytical hierarchy process based approach to the process of railway risk information: A railway risk management system

Risk management is becoming increasingly important for railway companies in order to safeguard their passengers and employees while improving safety and reducing maintenance costs. However, in many circumstances, the application of probabilistic risk analysis tools may not give satisfactory results because the risk data are incomplete or there is a high level of uncertainty involved in the risk data. This article presents the development of a risk management system for railway risk analysis using fuzzy reasoning approach and fuzzy analytical hierarchy decision making process. In the system, fuzzy reasoning approach (FRA) is employed to estimate the risk level of each hazardous event in terms of failure frequency, consequence severity and consequence probability. This allows imprecision or approximate information in the risk analysis process. Fuzzy analytical hierarchy process (fuzzy-AHP) technique is then incorporated into the risk model to use its advantage in determining the relative importance of the risk contributions so that the risk assessment can be progressed from hazardous event level to hazard group level and finally to railway system level. This risk assessment system can evaluate both qualitative and quantitative risk data and information associated with a railway system effectively and efficiently, which will provide railway risk analysts, managers and engineers with a method and tool to improve their safety management of railway systems and set safety standards. A case study on risk assessment of shunting at Hammersmith depot is used to illustrate the application of the proposed risk assessment system.     

不同结构的树脂复鞣剂在皮革中形态的电镜研究

借助扫描电镜(SEM)观察了SCC丙烯酸皮革填充树脂、ART丙烯酸树脂复鞣剂、HMP多功能皮革材料以及RTM三聚氰胺树脂复鞣剂等4种高分子材料在皮革中的微观结构，讨论了每种材料赋予皮革的不同性能，为制革工作者在制革时正确选择皮化材料提供参考。