【作者】 蔡浩鹏；

【导师】 王钧；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 PP/GMT(Glass Mat Reinforced Polypropylene Sheet)复合材料是连续玻璃纤维毡或连续玻璃纤维针刺毡为增强材料与改性聚丙烯为基体复合而成的一种片材。GMT的比强度高，抗冲击性优异；采用压缩模塑工艺，GMT片材可以制造尺寸大、稳定性好、形状复杂的部件，在汽车制造上有广泛的应用前景。 国产悍马军车是我国下一代陆军装备，其挡泥板设计为PP/GMT材质。该挡泥板由三个相互垂直面组成，产品厚度仅为3mm，但高度最大达到了约200mm，是一种超高度／厚度比的复杂制品。本课题研究的主要目的是制定模具设计方案，优化成型工艺参数(温度、压力制度等)，研制出满足国产悍马军车挡泥板设计要求的制品；同时结合产品的研制，对GMT材料的流动性能、热传导性能进行初步的探索，为GMT制品的工业生产提供指导。 本文首先在恒温条件下通过挤压圆盘形GMT坯料，对材料的流动性能进行了研究。1)通过测量挤压流动后不同半径范围内的纤维含量，研究了压力、温度等对材料流动性能的影响。研究表明：GMT材料具有很好的充模流动性，流动过程中纤维毡保持一个整体；GMT材料挤压流动行为表现为各向同性；温度、压力制度对纤维的均匀分布影响很大：2)通过测量不同合模速率下压力变化，采用拉伸粘度模型(Extensional viscosities model)和纯剪切流动模型(Shear force model)对数据进行分析，导出了描述GMT材料宏观行为的流变学参数。对比模型计算结果和实验结果，分析了模型的理论缺陷。拉伸粘度模型的计算结果与实验结果吻合得相当好表明：在合模速率不大或变形率不是很大的情形下，挤压流动过程中剪切力相对于拉伸应力可以忽略。 其次，由于该产品是薄壁件，平面上的尺寸比厚度大得多，可假设为无限大的平板。以此为基础，建立模型对GMT在模具内冷却过程进行模拟。结果表明：在模具内冷却，材料表面和中心的温度很快的达到一致。当模具温度为80℃时，220℃的片材经过30s左右材料中心和边缘的温度几乎一样，为130℃左右。 通过研究温度对GMT材料的力学性能(弯曲强度)、表面质量的影响，得到了优化的工艺参数。研究表明:通过选择合理的温度、压力制度可以压出具有良好的表面质量、优异的力学性能的制品。 在上述实验结果的基础上，设计了国产悍马军车挡泥板模具，确定了产品的压力制度和温度制度，成功的压制出了国产悴马军车挡泥板。产品性能测试表明，性能满足设计要求。更多还原

【Abstract】 PP/GMT (Glass Mat Reinforced Polypropylene Sheet) are made from continuous glass fiber mat or needle mat reinforce modified Polypropylene matrix. GMT has high specific strength as well as excellent impact strength and can be made into large size complex component by compression molding. It has broad applications in automobile industry.Hummer is the equipment for the army of our nation in the future. Its fender is design of PP/GMT composite. The shape of the fender is composed of three inter-vertical planes, which were only 3mm thick, but the length is more than 200mm. So it is a complicate product with superior length/thickness ratio. Our research is to design the mould arid optimize the molding parameters such as temperature and pressure and finally make the fender to meet the design requirements. Also the fluidity and thermal conductivity of GMT are studied and theoretically analyzedThe fluidity of GMT is studied by compressing the round shape GMT sheet under constant temperature. First, by measure the fiber content in different radius range, the influence of pressure and temperature on fluidity is investigated. It shows that the fiber mat keeps integrity during flow and the GMT has good fluidity for molding. We also found that the rheological behavior of single layer GMT is isotropic. Temperature and pressure method has great affection on the distribution of the fiber. Second, We measure the pressure change under different molding rate and use Extensional viscosities model and Shear Force Model to analysis the data. We get the rheological parameters of GMT. By compare the experiential simulate data to the real results, the advantages and disadvantages of each model are evaluated. The calculated value of Shear force model fit well with the experimental results. It means that compare to the tensile stress during squeeze flow the shear stress can be omitted especially when the molding rate is low and distortion rate is low.Since the fender is shell like component, the dimension of the plane is muchlarger than the thickness. So we suppose it as an infinite plane and build the model to simulate the cooling process of the GMT in the mold. It shows that when GMT cooling in the mold its surface temperature and center’s temperature are tend to be uniform quickly. When the mold is 80 C, the sheet cooling from 220 C and the temperature get uniform in 30 seconds, the center temperature is equal to the fringe temperature, which is 130 C.The influence of temperature and pressure on mechanical properties, surface quality and dimension precision are discussed and get the process parameters optimized. The products made by these methods have good surface quality and dimension precision and excellent mechanical properties. They meet the requests of Hummer’s fender.更多还原