热塑性树脂基复合材料的加工方法

简要介绍了为克服热塑性树脂熔融粘度大，浸渍纤维困难，而采用的加工方法。  

用于热塑复合材料的混合纱织造性能

 研究了由玻璃纤维和丙纶纤维组成的包芯编带纱、摩擦纺纱、空心锭子包缠纱以及玻璃纤维纱的织造性能。在设计的实验条件下,经过100次摩擦后,包芯编带纱表面只出现少许毛羽,纱线强力基本没有变化;摩擦纺纱的包覆纤维被完全剥离,纱线强力下降60%;空心锭子包缠纱在摩擦70次左右发生断裂;玻璃纤维纱产生大量的断丝,强力下降52%。三维织造实验表明,包芯编带纱具有优良的可织造性能,而上述其它的纱线难以进行织造加工,特别是难以织造高密织物和三维织物。  

三维机织热塑复合材料的制作与性能

 设计了一种以包芯编带纱为中间体制作三维机织热塑复合材料的方法。对复合材料的空隙率、拉伸、弯曲性能进行了实验和分析。研究表明,包芯编带纱既能满足热塑树脂的均匀渗透,又具有良好的三维织造性能;三维机织热塑复合材料的刚度较低,预拉伸工艺可以显著提高复合材料的拉伸刚度和弯曲刚度。  

正交三维织物增强热塑树脂复合材料的成型工艺对其弯曲性能的影响

主要研究了正交三维织物增强热塑复合材料的成型工艺，即成型厚度、成型温度对其弯曲性能的影响。这为得出复合材料的最佳成型工艺方案提供了一定的理论依据。  

Hybrid Yarns and Textile Preforming for Thermoplastic Composites

In the recent years, the use of textile structures made from high performance fibers is finding increasing importance in composites applications. In textile process, there is direct control over fiber placements and ease of handling of fibers. Besides economical advantages, textile technologies also provide homogenous distribution of matrix and reinforcing fiber. Thus textile performs are considered to be the structural backbone of composite structures. Textile technology is of particular importance in the context of improving certain properties of composites like inter-laminar shear and damage tolerance apart from reducing the cost of manufacturing. Textile industry has the necessary technology to weave high performance multifilament fibers such as glass, aramid and carbon, which have high tensile strength, modulus, and resistance to chemicals and heat into various types of preforms. Depending upon textile preforming method the range of fiber orientation and fiber volume fraction of preform will vary, subsequently affecting matrix infiltration and consolidation. As a route to mass production of textile composites, the production speed, material handling, and material design flexibility are major factors responsible for selection of textile reinforcement production. This opens a new field of technical applications with a new type of semifinished material produced by textile industry. Various types of hybrid yarns for thermoplastic composites and textile preforming methods have been discussed in detail in this issue. Information on manufacturing methods, structural details and properties of different hybrid yarns are presented and critically analyzed. Characterization methods used for these hybrid yarns have been discussed along with the influence of different processing parameters on the properties being characterized. The developments in all areas of textile preforming including weaving, knitting, braiding, stitching and nonwovens techniques are presented and discussed along with the characterization techniques for these preforms. The techniques used for manufacturing composites using hybrid yarns and textile preforms are discussed along with the details on compaction behavior of these structures during consolidation process. The structure of hybrid yarns and the textile preforms have direct influence on the properties of the composite made from them. The reported literature in this aspect is discussed in detail. In the end, the potential application areas and their trends for thermoplastic composites are discussed and analyzed.  

微编纱的开发与研制

为了解决三维机织热塑复合材料中三维机织预型件的织造和热塑基体浸入预型件这两大难题，开发了织造预型件的微编纱。此纱是将一种纤维采用编织绳带的方法，按照一定的比例均匀包覆在另一种纤维外部而形成，外覆纤维用丙纶，内部纤维用玻璃纤维。通过摩擦实验，表明该微编纱能有效地保护增强纤维，能满足织物组织较复杂的三维机织预型件的织造条件。对微编纱的加工原理、工艺参数的选定进行了分析、探讨，为三维机织热塑复合材料的生产加工开辟了一条新的途径。  

Analysis of flexural strength of preoxidized fiber-reinforced composites made by a nonwoven process and hot-pressing

Preoxidized fiber was used here as a reinforcement for the first time. Polypropylene fiber was used as resin matrix, and the preform with the two types of fiber was prepared by a nonwoven process. Then, hot-pressing was applied to make a treatment for the preform, and the thermoplastic composites reinforced with preoxidized fiber were prepared. The effects of the hot-pressing temperature, hot-pressing pressure, weight percentage of preoxidized fiber, and nonwoven process on bending failure strength along the machine direction (MD) and transverse direction (CD) were studied under a three-point bending load. It was concluded that the flexural strength of the composites along MD and CD decreases with increasing hot-pressing temperature and hot-pressing pressure, while an initial increase and then decrease was observed with the increase in the weight percentage of preoxidized fiber. However in both directions, flexural strength of the composites is influenced significantly by the nonwoven process. Finally, the bending failure mode of the composites generated micro-flaws, which can be observed on the center surface of the composites. The micro-flaws extend to the ends along the thickness direction of the composites, and plastic bending failure is observed due to partial delamination.  

Impact properties of thermoplastic composites

The excellent properties exhibited by thermoplastic composites at much reduced weight have attracted attention in the development of products in different sectors. Thermoplastic (TP) composites, because of their distinctive properties as well as ease of manufacturing, have emerged as a competitor against the conventional thermoset resin-based composites. Depending on the application, these composites may undergo impact events at various velocities and often fail in many complex modes. Hence, the development of TP composites having high energy-dissipation at (the desired) much-reduced weight has become a challenging task, but it is a problem which may be alleviated through the appropriate selection of materials and fabrication processes. Furthermore, fibre surface modification has been shown to increase fibre-matrix interfacial adhesion, which can lead to improved impact resistance. Textile preforms are helpful in acting as a structural backbone in the composites since they offer a relatively free hand to the composite designer to tailor its properties to suit a specific application. Additionally, hybrid textile composite structures may help in achieving the desired properties at much lower weight.

Simulation software can play a significant role in the evaluation of composites without damaging physical samples. Once the simulation result has been validated with actual experimental results, it should be possible to predict the test outcomes for different composites, with different characteristics, at different energy levels without conducting further physical tests. Various numerical models have been developed which have to be incorporated into these software tools for better prediction of the result.

In the current issue of Textile Progress, the effects of various materials and test parameters on impact behaviour are critically analyzed. The effect of incorporating high-performance fibres and natural fibres or their hybrid combination on the impact properties of TP composites are also discussed and the essential properties of TP polymers are briefly explained. The effects of fibre and matrix hybridization, environmental factors, various textile preform structures and fibre surface modification treatments on the impact properties of thermoplastic composites are examined in detail. Various numerical models used for impact analysis are discussed and the potential applications of TP composites in automobile, aerospace and medical sectors are highlighted.