本文關鍵詞： 預成型體 干纖維鋪放 預成型條件 滲透率 壓縮特性 力學性能　出處：《東華大學》2017年碩士論文　論文類型：學位論文

【摘要】：目前在航空復合材料領域普遍采用熱壓罐工藝,但是隨著復合材料制件應用范圍越來越廣,用量越來越大,熱壓罐工藝存在的問題不斷暴露出來:一是熱壓罐設備以及預浸料運輸和儲存的成本較高;二是較難實現大型制件的一體化成型,周期較長、效率較低。為克服這些缺點,滿足成本和時間效率要求,干纖維鋪放樹脂浸漬工藝應運而生。本文模擬干纖維鋪放的原理,將連續(xù)熱塑性纖維(定型纖維)鋪放在碳纖維鋪層中間,經熱壓制備預成型體,并結合VARI工藝制備復合材料制件。本文具體研究內容和主要結論如下:(1)制備了不同熱壓工藝條件及不同定型纖維用量的預成型體,并對預成型體的滲透特性進行了研究。結果表明,預成型壓力越小,預成型的溫度越低,定型纖維含量越接近3.6%左右,預成型體滲透率越大,更利于樹脂的浸漬。(2)研究了不同熱壓工藝條件及不同定型纖維用量的預成型體的壓縮特性。結果表明,預成型壓力越大,預成型溫度越高,預成型體壓縮剛度越大,具有較強抵抗變形的能力;預成型體的壓縮剛度隨著預成型纖維用量的增加,呈現先提高后降低的規(guī)律,當定型纖維含量在2.4%左右時,預成型體的剛性較好。(3)制備了不同預成型壓力工藝條件下的預成型體,并測試了預成型體采用VARI工藝制備成復合材料的厚度、纖維體積含量、力學性能和微觀結構。結果表明,隨著預成型壓力的增大,復合材料纖維體積含量增大,當預成型壓力達到1MPa后,纖維體積含量達到最大值65%左右;0°拉伸模量與彎曲模量隨著預成型壓力的增大不斷升高,并最終達到150GPa和125GPa;而0°拉伸強度和短梁剪切強度呈現先增大后減小的趨勢,在預成型壓力達到0.6MPa時最高;90°拉伸模量和90°拉伸強度基本保持不變。(4)測試了不同預成型溫度條件下制備的復合材料的性能,并表征了其微觀結構。結果表明,預成型溫度低于或在定型材料軟化溫度范圍內時,隨著預成型溫度的增大,復合材料性能均有提高;而預成型溫度高于定型材料軟化溫度后,定型材料會發(fā)生軟化,甚至熔化,會影響樹脂的浸潤,進而產生缺陷,導致復合材料強度降低。(5)考察不同定型纖維用量對復合材料的厚度、纖維體積含量、力學性能的影響規(guī)律,并對其微觀結構進行觀察研究。結果表明,隨著定型纖維含量的不斷增加,復合材料試樣厚度增大,碳纖維體積含量減小,力學性能降低。通過金相顯微觀察可以發(fā)現,夾雜在碳纖維之間的聚氨酯纖維成型后相當于樹脂富集區(qū),這種富集區(qū)的存在,會使得碳纖維體積含量降低,導致復合材料力學性能降低。
[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 擄increase with the increase of preforming pressure, and finally reach 150 GPA and 125 GPA. However, the tensile strength of 0 擄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 擄and tensile strength of 90 擄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.
【學位授予單位】：東華大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB33

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