GLARE层板滚弯成形的理论分析与试验研究

发布时间：2018-10-23 08:47

【摘要】：作为第二代纤维金属层板,GLARE层板综合了复合材料和金属材料的各种优异性能,目前该类层板的研究热点主要集中于制备工艺、复杂构件成形方法以及服役性能评价等。因此,本文针对GLARE层板的滚弯成形理论与工艺技术开展了系统地研究分析,为GLARE层板在大型飞机上的应用提供理论依据和工程指导。首先,通过试验研究了GLARE层板的基本成形性能。结果可知,采用n yσ=σ+Kε本构模型来拟合真实应力-应变曲线,其拟合结果最优。GLARE 2A层板的抵抗拉伸变形能力最强,很难产生厚向变形,因此其压延成形性能较差。在弯曲变形过程中,GLARE 6A层板的相对弯曲角最小,并且GLARE 6A层板的弯曲回弹量最小,表现出良好的弯曲成形性能。其次,通过理论分析建立了GLARE层板滚弯成形的解析模型。采用Hill屈服准则和指数强化模型来描述各向异性的铝合金板材,分析计算了弯曲成形过程中GLARE层板的应力应变分布、弯矩大小以及理论回弹半径和回弹角,建立了层板滚弯成形的解析模型。通过试验验证了解析模型的准确性,表明所建立的解析模型具有一定的适用性。随后,通过试验研究分析了上辊下压量、纤维铺层方式以及层板结构三个参数对其滚弯回弹规律的影响。研究结果表明,上辊下压量越大,GLARE层板的回弹越小,并且上辊下压量与层板的弯曲成形半径之间的关系曲线符合幂函数关系。保持上辊下压量相同情况下,GLARE2A层板的回弹量最大,GLARE 3层板次之,GLARE 6A层板最小。GLARE层板的回弹量是随着结构的增加而逐渐减小,并且减小的幅度趋向于稳定。另外,采用腐蚀去层法分析了滚弯成形后GLARE层板的残余应力分布情况,分析结果表明,层板的外表面及其整个铝合金层均处于压应力状态,但是不同类型GLARE层板铝合金层的残余应力变化规律并不明显。最后,利用SEM对滚弯成形后的GLARE层板损伤失效特征进行了观察分析,得到了层板的临界下压量和临界成形曲率半径。结果表明,当上辊下压量达到12 mm时,玻璃纤维达到极限应变,层板发生损伤失效,以GLARE 2A层板为研究对象,由此可确定,在滚弯成形过程中,临界上辊下压量为11 mm,对应的临界弯曲曲率半径为172.47 mm。当上辊下压量达到12 mm时,三种纤维铺层方式的GLARE层板均发生一定程度的损伤失效,其失效形式主要表现为树脂基体挤压破坏、基体开裂以及纤维断裂,但都没有出现界面分层现象。当GLARE层板从3/2结构依次增大为4/3、5/4、6/5结构时,层板的损伤失效程度也随之变大。
[Abstract]:As the second generation fibrous metal laminates, GLARE laminates integrate various excellent properties of composite materials and metal materials. At present, the research focus of this kind of laminates is mainly on the preparation process, the forming methods of complex components and the evaluation of service performance. Therefore, in this paper, the theory and technology of roll bending forming of GLARE laminates are systematically studied and analyzed, which provides theoretical basis and engineering guidance for the application of GLARE laminates in large aircraft. Firstly, the basic formability of GLARE laminates was studied by experiments. The results show that the true stress-strain curve is fitted by the constitutive model of ny 蟽 = 蟽 K 蔚, and the fitting result is optimal. The GLARE 2A laminate has the strongest resistance to tensile deformation and is difficult to produce thick deformation, so the forming property of GLARE 2A laminate is poor. In the process of bending deformation, the relative bending angle of GLARE 6A laminates is the smallest, and the flexural springback of GLARE 6A laminates is the least, which shows good bending formability. Secondly, the analytical model of GLARE sheet roll forming is established by theoretical analysis. Hill yield criterion and exponential strengthening model are used to describe anisotropic aluminum alloy sheet. The stress and strain distribution, bending moment, theoretical springback radius and springback angle of GLARE laminates during bending forming are analyzed and calculated. The analytical model of laminate rolling forming is established. The accuracy of the analytical model is verified by experiments, which shows that the established analytical model is applicable to some extent. Then, the influence of three parameters, such as the pressure of upper roll, fiber layer and laminate structure, on the springback rule of roll bending is analyzed. The results show that the higher the pressure is, the smaller the springback of the GLARE laminate is, and the curve between the roll down pressure and the bending radius of the laminate is in accordance with the power function. When the upper roll pressure is the same, the springback of GLARE2A laminates is the largest, that of GLARE 3 laminates is the second, and that of GLARE 6A laminates is the smallest. The springback of GLARE laminates decreases gradually with the increase of structure, and the decreasing amplitude tends to be stable. In addition, the residual stress distribution of GLARE laminates after roll forming is analyzed by corrosion delamination method. The results show that the external surface of the laminate and its whole aluminum alloy layer are in the state of compressive stress. However, the variation of residual stress in different types of GLARE laminate aluminum alloy layer is not obvious. Finally, SEM was used to observe and analyze the damage failure characteristics of GLARE laminates after rolling forming, and the critical compression and curvature radius of the laminates were obtained. The results show that when the pressure of top roll reaches 12 mm, the glass fiber reaches the limit strain and the laminate is damaged and invalidated. Taking the GLARE 2A laminate as the research object, it can be determined that in the process of rolling forming, The critical bending curvature radius corresponding to the critical roll down pressure of 11 mm, is 172.47 mm.. When the pressure of the top roller reaches 12 mm, the GLARE laminates with three kinds of fiber laminates have a certain degree of damage and failure. The main failure forms are extruding failure of resin matrix, cracking of matrix and fiber fracture. However, there is no phenomenon of interface delamination. When the structure of GLARE laminates increases from 3 / 2 to 4 / 3 / 5 / 4 / 5, the damage failure degree of the laminates also increases.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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