亚麻增强树脂基复合材料的开发与研究

【作者】 刘丽妍；

【导师】 黄故；

【作者基本信息】 天津工业大学 ， 纺织工程， 2005， 博士

【摘要】 我国亚麻资源丰富,与玻璃纤维等无机纤维相比,具有较高的比强度、比模量。同时亚麻容易种植,生长周期短,具有天然可降解性,可以作为绿色复合材料的理想增强材料。利用这一资源优势,课题选取亚麻为主要原料,进行亚麻纤维增强热固、热塑性树脂基复合材料的开发和研究,制备出性价比较高、力学性能较优的复合材料板材,为工程应用提供理论依据。 课题着重研究了亚麻纤维增强热塑性树脂基复合材料的制备以及性能测试。作为对比和参考,首先加工出针刺亚麻纤维毡作为增强体,与不饱和聚酯树脂及环氧树脂进行复合,制备出亚麻增强热固性树脂基复合材料板材,并进行性能测试和分析。 考虑热塑性树脂粘性大,成型困难以及加工成本等问题,课题利用亚麻纤维的可纺性,选取密度较小的聚丙烯作为热塑性基体,通过与亚麻纱线捻合,形成PP包覆亚麻的纱线结构,实现基体与纤维的丝束级均匀混合。 分别制备了45%、50%和60%三种纤维体积含量的包覆纱线,采用机织的方法加工出复合材料预制件,经过层合热压制得亚麻/PP复合材料。通过调节压力、温度,确定了热压工艺;在不同纤维体积含量、不同铺层数、以及不同组织的条件下,进行板材拉伸、冲击性能测试,并对测试结果进行了分析和讨论。结果表明纤维在复合材料中的状态对材料的性能起到重要作用。纬纱在板材中的伸直状态好于经纱,所以同种工艺中,纬向的拉伸性能、经向的冲击性能(纬纱为主要的承力单元)均较高;不同组织中,由于斜纹组织中纱线的伸直状态良好,所以其板材的拉伸、冲击性能均优于平纹组织。 对纤维浸渍过程、板材的固化成型过程进行模型分析及数值模拟;分析了孔隙产生的原因并计算孔隙率的具体数值;通过板材的拉伸试验,利用多项式拟合,得到板材经、纬向纤维伸直系数a_j、a_w与对应断裂伸长率的关系式,从而给出相关的强度修正公式;运用有限元分析软件ANSYS分别对亚麻增强热固性、热塑性树脂基复合材料的拉伸过程进行计算机编程,模拟拉伸破坏过程。结合亚麻增强热固性、热塑性复合材料的SEM拉伸断口破坏形貌,分析了纤维增强与板材破坏机理。更多还原

【Abstract】 Flax is abundant in China and flax fiber has higher strength and modulus--density ratio compared with other inorganic fibers such as glass fiber. It is easy to cultivate and its growth period is shot. As a result flax fiber can be decomposed naturally;it could be used as an ideal reinforcing material of environmental protection composites. Flax fiber was used to fabricate with thermo-setting and thermo-plastic resins in this research. Laminates with high property-cost ratio were developed and researched;the results may be important reference for engineering applications theoretically.Flax reinforced thermo-plastic composites were mainly analyzed in this paper. For comparison, first flax fiber was needle-punched to form the mats, then fabricated with unsaturated polyester (UP) and epoxy (EP) separately. The mechanical properties of these composites were tested and analyzed.Polypropylene (PP), which has the lowest density among man-made fibers, was used as the thermo-plastic matrix. Te overcome the difficulties of resin penetrating during the composite processing because of the high viscosity, commingled yarns were produced by PP filaments wrapping around the linen yarn. The even distribution of flax and PP in the yarn gave a better mixture of the matrix and reinforcing material, and the reduction in cost was also realized to some extend.Commingled yarns with volume fraction of 45%, 50% and 60% were processed and woven into fabric as the pre-pregnant. Then fabric was sandwiched into laminates by optimum hot-pressing technology that was chosen through testing the parameters such as pressure and temperature during experiment. The laminates with different volume fractions, layers, and woven structures were tested by the tensile and impact instruments. Analysis revealed that fiber status in laminates was the most important factor affecting the mechanical properties. Since the weft yarns straightened better than warp yarns in laminates with the same manufacture technology, the tensile property in fill direction and impact behavior in warp direction were much better. As far as the woven structures were concerned, the mechanical properties of laminateswith twill structure were better than those with plain structure.The fiber impregnation process was analyzed with the help of model and the shaping process was numerically simulated. The reason of the void was analyzed and the numerical value of the content was calculated as well. As for the tensile results, the revised formula for tensile strength was conducted. Two yarn straightened coefficients a,, aw were quoted to the formula, which were related to the extending ratio at break of laminates, and the expressions were defined by polynomial fit.The tensile processes of flax reinforced thermo-setting & thermo-plastic composites were programmed and simulated by using ANSYS, the software of Finite Element Analysis (FEA). The mechanisms of fiber reinforcing and fracture were discussed through examining the fracture photographs of Scanning Electronic Microscope (SEM).更多还原