三维机织热塑复合材料制作微结构力学性能及复合固化过程的研究

【作者】 董卫国；

【导师】 黄故； 马崇启；

【作者基本信息】 天津工业大学 ， 纺织工程， 2003， 博士

【摘要】 热塑复合材料是以各种热塑树脂为基体，以玻璃纤维、碳纤维等各种增强纤维为增强材料的复合材料的总称。热塑性材料有许多优于热固性材料的优点：较好的韧性、耐破坏性；使用寿命长、制成率高、可循环利用及生产周期短等。与热固性复合材料相比，先进的热塑性复合材料的最重要、最具潜力的优点是生产过程的自动化，能低成本地生产。将来热塑基体复合材料被广泛地、扩大化地应用是在预料之中的，特别是混纤热塑性复合材料在近几年已经得到了较快的发展和广泛的应用。虽然人们已经认识到长纤维增强热塑复合材料的优点和在制作结构件方面的潜力，但是，具有低成本效益的、实用的生产工艺的开发和研究只有十年多的历史。目前应用较成熟的加工工艺主要有拉挤成型、缠绕成型、二维织物或单向带的叠层模压成型等。 三维机织物作为纺织结构复合材料的预制件，具有良好的整体性，是理想的结构复合材料。其抗层间剪切强度、抗冲击性、损伤容限、断裂韧性、可靠性等综合力学性能皆优于传统的层合复合材料。三维结构的纺织预型件加工技术的研究已有20年的历史，虽然取得了重要进展，但是三维织造的运动配合复杂、纱线之间的交织摩擦大，特别是玻璃纤维、碳纤维等高性能纤维的脆性较大，在加工过程中，极易被损伤。而且由于开口不清，为织造加工带来了极大的困难，大大限制了织造效率的发挥。 本课题设计了一种高效低成本三维机织热塑复合材料的制作工艺，以微编纱做为中介媒体，使其同时满足热塑树脂的快速均匀浸润、苛刻的三维立体织造条件的要求，为三维织造和热塑复合材料地制作开辟一条新的途径。建立了纤维-树脂受力模型，在此基础上建立了树脂径向有限渗透模型、树脂轴向渗透模型。由两相流体动力学理论建立树脂-气体在纤维介质中的渗流模型。这些模型能对已有的实验结果做出很好的解释，并为本课题的实验所证实。通过试验和理论分析，建立了连续纤维增强的三维机织热塑复合材料工艺条件-微观结构-力学性能之间摘要的关系，为确定合理的加工工艺和提高复合质量提供了理论依据。 微编纱的包缠纤维对芯纱的包缠紧密、牢固，纱线表面毛羽少，在无上浆条件下有良好的织造性能。增强纤维(芯纱)的直径越小，复合质量越好，但当芯纱的直径较小时，纺纱效率低。三维织物结构的几何模型表明:影响接结经取向角的因素主要包括纬纱压扁系数、接结经的接结方式、接结经短径以及纬密。几何模型计算织物的纤维体积密度与实测密度相符。 复合工艺参数主要包括温度、压力和时间。提高浸渍温度可以降低树脂的粘度，提高树脂的渗透性能。PP树脂的温度在160一200℃范围内，温度对粘度的影响较大，超过200℃后，粘度变化较小。实验表明:温度大于180℃时，树脂易外溢，而且表层树脂颜色变暗，树脂被氧化分解。压力的大小影响纤维束之间的紧密结合、树脂在纤维束中的渗透、树脂在材料中的溢出，要根据织物的结构，树脂的温度等因素确定。最大压力以能够达到试样完全渗透时的厚度为限。由于树脂受力的衰减和纤维束孔隙率的减小，树脂在纤维束中的渗透是一个有限过程，延长浸渍时间不能保证树脂在纤维束中的完全渗透。因此，纱线中增强纤维的直径大小是决定树脂能否完全渗透的最重要的因素，减小微编纱中增强纤维的直径是保证良好的复合质量的最关键措施。 模压成型使试样的厚度减小，经纱由原来的平面曲线变为扭曲的空间曲线，扭曲程度和形状与接结经的取向角、试样压缩的程度、接结经的密度有关。复合固化后，纬纱仍然保持直线状态，但纬纱的压扁系数增加。接结经的截面接近圆形，其压扁程度小于纬纱。 接结经的形态对材料的力学性能有重要的影响，结接经弯曲变形大，材料的拉伸模量和弯曲模量小，伸长大，材料表现出较好的柔性。经预拉伸后的试样，接结经的取向角小，弯曲变形小，材料表现出低伸、高强、高模量的特点。实验表明:经10%的预拉伸后，材料的断裂伸长减小65肠，断裂强度提高92%，模量提高3.6倍。弯曲强度提高28%，弯曲刚度提高5倍。复合质量对材料的拉伸强度、拉伸模量、弯曲强度、弯曲模量有明显的影响。更多还原

【Abstract】 Thermoplastic composite is the general term of composite based on thermoplastic resin and reinforced by all kinds of reinforcing fibers, such as glass fiber, carbon fiber. Thermoplastic composites have a number of important advantages over thermosetting composites for instance, better toughness/damage tolerance, longer service life, recyclable, and shorter processing period. The most important and potential advantage of thermoplastic composite is the automatization of processing, which can reduce the costs of the final products. Therefore, it is predictable that thermoplastic composites will come into use in a rapid and wide way in the future. Especially thermoplastic composites with commingled fiber have been developed rapidly and used widely in recently years. Though people have realized the advantages and potentials of thermoplastic composites in structure manufacture, the development and study of practical processing technique has been conducted only in recent ten years. At present, the successful application processes mainly are pultrusion process, winding and uni-direction band compressing molding process, etc.Three-dimensional fabric used as preform of weaving structural composite is ideal material with excellent integrity; its toughness, damage tolerance and reliability are better than traditional materials. The research of there-dimensional preform has a history over twenty years, though great progress has been made, high performance fibers such as glass fiber and carbon fiber are easy to be damaged because of the complex motion and the great friction between fibers during fabric production, which limits the weaving efficiency greatly.In this paper, a kind of low-cost but effective manufacturing technology of 3D woven thermoplastic composites is designed, and micro-braided yarn is chosen asthe medium to meet the requirement of rapid, even impregnating and rigorous 3D weaving condition, which inaugurates a new approach for weaving 3D weave and producing thermoplastic composites. Along with the fiber-resinimpregnating model’s construction, the transverse finite impregnating model and lognitudinal-impregnating model of fibers are also constructed. Theimpregnating and flowing patterns of resin-air among the fibers are established according to the theory of two-phase fluid dynamism. These models can explain the results of the experiment done before and are proved to be correct by the experiment of this research. The relationships among the processing-microstructure-property of the 3D woven thermoplastic composites are established, which offer theoretical foundation for determining the reasonable processing technique and improving the composites’ quality.The core yarn is wrapped tightly and firmly by micro-braided yarn’s wrapping fibers with little hair on its surface and has good weaving properties under the circumstances of non-sizing. The less the diameter of reinforcing fiber (core yarn), the better quality of the final material. However, when the core’s diameter is too small, the spinning efficiency is low. The geometry model of 3D woven structure indicates that the factors that influence the binder orientation angle mainly include the aspect ratio of weft yarn cross section, binding pattern, the shot diameter of binder and weft density. A good agreement is demonstrated between theoretical predictions and experimental results.Temperature, pressure and time are the most important parameters in the fabrication process. Rising temperature may reduce resin viscosity. Temperature has great influence on viscosity of the resin when melting point of PP resin is within 160 ~200 C; but viscosity varies slightly over 200 C. Experiment demonstrates when temperature is over 180掳C, resin overflows easily, and the surface resin’s color becomes faint. The processing pressure which influences the combination state, the flowing behavior of the matrix among the fiber bundles, the overflowingcharacter should be determined by the woven structure, the temperature更多还原