热压预成型参数对真空辅助成型复合材料性能的影响

发布时间：2018-01-20 00:48

本文关键词： 预成型体干纤维铺放预成型条件渗透率压缩特性力学性能　出处：《东华大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前在航空复合材料领域普遍采用热压罐工艺,但是随着复合材料制件应用范围越来越广,用量越来越大,热压罐工艺存在的问题不断暴露出来:一是热压罐设备以及预浸料运输和储存的成本较高;二是较难实现大型制件的一体化成型,周期较长、效率较低。为克服这些缺点,满足成本和时间效率要求,干纤维铺放树脂浸渍工艺应运而生。本文模拟干纤维铺放的原理,将连续热塑性纤维(定型纤维)铺放在碳纤维铺层中间,经热压制备预成型体,并结合VARI工艺制备复合材料制件。本文具体研究内容和主要结论如下:(1)制备了不同热压工艺条件及不同定型纤维用量的预成型体,并对预成型体的渗透特性进行了研究。结果表明,预成型压力越小,预成型的温度越低,定型纤维含量越接近3.6%左右,预成型体渗透率越大,更利于树脂的浸渍。(2)研究了不同热压工艺条件及不同定型纤维用量的预成型体的压缩特性。结果表明,预成型压力越大,预成型温度越高,预成型体压缩刚度越大,具有较强抵抗变形的能力;预成型体的压缩刚度随着预成型纤维用量的增加,呈现先提高后降低的规律,当定型纤维含量在2.4%左右时,预成型体的刚性较好。(3)制备了不同预成型压力工艺条件下的预成型体,并测试了预成型体采用VARI工艺制备成复合材料的厚度、纤维体积含量、力学性能和微观结构。结果表明,随着预成型压力的增大,复合材料纤维体积含量增大,当预成型压力达到1MPa后,纤维体积含量达到最大值65%左右;0°拉伸模量与弯曲模量随着预成型压力的增大不断升高,并最终达到150GPa和125GPa;而0°拉伸强度和短梁剪切强度呈现先增大后减小的趋势,在预成型压力达到0.6MPa时最高;90°拉伸模量和90°拉伸强度基本保持不变。(4)测试了不同预成型温度条件下制备的复合材料的性能,并表征了其微观结构。结果表明,预成型温度低于或在定型材料软化温度范围内时,随着预成型温度的增大,复合材料性能均有提高;而预成型温度高于定型材料软化温度后,定型材料会发生软化,甚至熔化,会影响树脂的浸润,进而产生缺陷,导致复合材料强度降低。(5)考察不同定型纤维用量对复合材料的厚度、纤维体积含量、力学性能的影响规律,并对其微观结构进行观察研究。结果表明,随着定型纤维含量的不断增加,复合材料试样厚度增大,碳纤维体积含量减小,力学性能降低。通过金相显微观察可以发现,夹杂在碳纤维之间的聚氨酯纤维成型后相当于树脂富集区,这种富集区的存在,会使得碳纤维体积含量降低,导致复合材料力学性能降低。
[Abstract]:At present, hot pressing tank technology is widely used in the field of aeronautical composite materials, but with the application of composite materials more and more extensive, the amount of materials is increasing. The problems of hot pressing tank technology are exposed continuously: first, the cost of transportation and storage of hot pressing tank equipment and prepreg materials is high; Second, it is difficult to realize the integration of large parts, long cycle, low efficiency. In order to overcome these shortcomings, to meet the cost and time efficiency requirements. Dry fiber placement resin impregnation technology came into being. In this paper, the principle of dry fiber placement was simulated, continuous thermoplastic fiber (finalized fiber) was placed in the middle of carbon fiber layer, and the preform was prepared by hot pressing. In this paper, the main research contents and conclusions are as follows: 1) the different hot pressing process conditions and different fiber content of the preforms were prepared. The results show that the lower the preforming pressure, the lower the preforming temperature, the closer the fiber content is to 3.6%, and the greater the preform permeability is. The compression characteristics of preforms with different hot pressing conditions and different fiber content were studied. The results showed that the higher the preforming pressure, the higher the preforming temperature. The greater the compression stiffness of the preform is, the stronger the resistance to deformation is. With the increase of preform fiber content, the compression stiffness of the preform increased first and then decreased, when the fiber content was about 2.4%. The thickness and fiber volume content of the composite prepared by VARI process were measured. Mechanical properties and microstructure. The results show that the fiber volume content increases with the increase of preforming pressure, and the maximum value of fiber volume content is about 65% when the preforming pressure reaches 1 MPA. The tensile modulus and flexural modulus of 0 掳increase with the increase of preforming pressure, and finally reach 150 GPA and 125 GPA. However, the tensile strength of 0 掳and the shear strength of the short beam increased first and then decreased, and reached the highest when the preforming pressure reached 0.6 MPA. The properties of the composites prepared at different preforming temperatures were tested and the microstructure was characterized. The tensile modulus of 90 掳and tensile strength of 90 掳remained almost unchanged. When the preforming temperature is lower than or within the softening temperature range, the properties of the composites are improved with the increase of the preforming temperature. When the preforming temperature is higher than the softening temperature of the molding material, the molding material will soften or even melt, which will affect the resin wetting and then produce defects. The effect of different fiber content on the thickness, fiber volume content and mechanical properties of the composite was investigated, and the microstructure of the composite was studied. With the increasing of the fiber content, the thickness of the composite material increases, the volume content of carbon fiber decreases and the mechanical properties decrease. The polyurethane fibers intermingled between carbon fibers are equivalent to resin rich areas after molding. The existence of such rich zones will reduce the volume content of carbon fiber and lead to the decrease of mechanical properties of composites.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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