碳纤维增强塑料的涡流热成像检测研究

发布时间：2019-06-21 01:16

【摘要】：碳纤维增强复合塑料,是一种常见的高强度、轻质量的优质复合材料,常用于环境要求较高的航空航天领域、桥梁结构的加强件、新能源汽车车身部件、有高强度需求的体育器材等。碳纤维增强复合材料的大量应用给无损检测技术和无损评估带来了新挑战,本文旨在评估锁相涡流热成像技术对各种复杂程度的碳纤维增强塑料的检测效果。本研究过程按照被检测材料的复杂程度度,分为三个阶段。第一,针对厚度约1毫米的单向非编织的碳纤维增强复合塑料,顺纤维方向上的导电导热特性更高,属于各向异性材料。使用矩形线圈进行涡流热成像检测,实验观察到在矩形线圈弯角处的材料被加热区域内,存在沿碳纤维走向的明显长条低温区域,并将该区域为加热盲区,通过加做试块旋转实验和改变感应线圈的夹持模式,尝试圆形、盘饼形和亥姆霍兹线圈分别重复上述实验,否定了特定线圈-材料几何位置的原因,排除了线圈几何形状的影响。有限元仿真结果排除了材料本身存在缺陷的可能。第二,在评估了最简碳纤维材料之后,需要明确该技术对真实使用的材料,即对更为复杂的材料的检测能力,对双向六层纤维压合板进行热成像加测,结果表明相位图能够清晰地展现多层材料的纤维纹理,并通过拟合幅值信号与调制频率的关系,确定了该材料的涡流加热属于体加热方式。第三,进行了多层编织碳纤维材料的冲击损伤涡流热成像检测实验,并对比LED阵列光学热成像与三维计算机辅助断层扫描的检测效果,发现当冲击能量超过3 J时,涡流热成像的损伤检测效果优于LED光学热成像。除对以上三种不同复杂程度材料的实验评估,材料内部涡流分布的数值仿真结果可表明:垂向于纤维走向的涡流分量只有顺纤维走向涡流分量的百分之一,却是决定加热效果的首要因素。至此,各向异性碳纤维材料的加热特性得以部分确定。该研究评估了涡流热成像在不同复杂等级的碳纤维增强复合塑料上的检测效果。明确了单向纤维的感应可加热性,且加热盲区现象的发现及解读也填补了以往单向碳纤维涡流加热效果研究的空白,研究还分析了涡流热成像对冲击损伤的检测有效性,为这种材料的无损检测提供了新的解决思路。
[Abstract]:Carbon fiber reinforced composite plastic is a common high strength, light quality composite material, which is often used in aerospace field with high environmental requirements, reinforcement of bridge structure, body parts of new energy vehicle, sports equipment with high strength demand and so on. The extensive application of carbon fiber reinforced composites has brought new challenges to nondestructive testing technology and nondestructive evaluation. The purpose of this paper is to evaluate the testing effect of phase-locked vortex thermal imaging technology on carbon fiber reinforced plastics with various complexity. According to the complexity of the tested materials, the process of this study is divided into three stages. First, for unidirectional non-braided carbon fiber reinforced composite plastics with thickness of about 1 mm, the conductive and thermal conductivity in the direction of fiber is higher, so it belongs to anisotropy material. Using rectangular coil to detect vortex thermal imaging, it is observed that there is an obvious long strip low temperature region along the direction of carbon fiber in the heating area of the material at the bending angle of the rectangular coil, and the area is regarded as the heating blind zone. By adding the test block rotation experiment and changing the clamping mode of the induction coil, the above experiments are repeated by circular, disk cake shape and Helmholtz coils, respectively. The reason of specific coil-material geometric position is denied, and the influence of coil geometry is excluded. The finite element simulation results rule out the possibility of defects in the material itself. Secondly, after evaluating the simplest carbon fiber material, it is necessary to clarify the detection ability of the technology to the more complex material, and to add thermal imaging to the bidirectional six-layer fiber compression plywood. The results show that the phase diagram can clearly show the fiber texture of the multi-layer material, and the Eddy current heating of the material belongs to the bulk heating mode by fitting the relationship between the amplitude signal and the modulation frequency. Thirdly, the experiment of vortex thermal imaging for impact damage of multi-layer braided carbon fiber materials is carried out, and the results of LED array optical thermal imaging and 3D computer aided tomography are compared. it is found that when the impact energy exceeds 3 J, the damage detection effect of vortex thermal imaging is better than that of LED optical thermal imaging. In addition to the experimental evaluation of the above three kinds of materials with different complexity, the numerical simulation results of the vortex distribution in the material show that the vortex component in the vertical direction of the fiber is only 1% of that in the direction of the fiber, but it is the first factor to determine the heating effect. At this point, the heating characteristics of anisotropic carbon fiber materials can be partially determined. In this study, the detection effect of swirl thermal imaging on carbon fiber reinforced composite plastics with different complex grades was evaluated. The induction heatability of unidirectional fiber is clarified, and the discovery and interpretation of heating blind zone phenomenon also fill in the blank of the previous study on the effect of unidirectional carbon fiber vortex heating. The study also analyzes the effectiveness of vortex thermal imaging in the detection of impact damage, which provides a new solution for the nondestructive testing of this kind of material.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ327.3

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