基于真实形貌孔隙模型的CFRP孔隙超声衰减特性研究

发布时间：2018-04-10 05:25

本文选题：CFRP　切入点：孔隙率　出处：《大连理工大学》2015年硕士论文

【摘要】：碳纤维增强复合材料(Carbon Fibre Reinforced Plastics, CFRP)孔隙率超声检测是无损检测领域的研究热点之一,其中超声衰减法应用最为广泛,该方法的理论模型主要包括规则孔隙模型和随机孔隙模型(Random Void Model, RVM),前者假设孔隙为规则几何形状、服从固定分布函数,与实际孔隙形貌差异较大,理论结果与实验结果存在较大偏差；后者将孔隙复杂、随机形貌考虑在内,理论结果与实验结果的偏差明显降低,但基于数学方法构建出来的孔隙与实际孔隙形貌仍然存在差异,且当样品中孔隙尺寸离散程度大时建模效果不理想。为了更加真实、准确地描述CFRP孔隙形貌,本文提出通过建立真实形貌孔隙模型(Real Morphology Void Model, RMVM)来研究CFRP孔隙率、孔隙形貌与超声衰减系数之间的复杂关系。研究对象为16层预浸料制备的单向CFRP层压板,采用连续切片法获得441张CFRP金相照片,通过中值滤波、二值化等图像处理方法对真实孔隙形貌特征进行原位提取,建立孔隙率范围在0.58%-3.49%之间的RMVM。采用时域有限差分法对RMVM进行数值模拟计算,得到衰减系数α孔隙率P变化的统计结果。研究表明,α随P增加而增加,二者呈α=0.905+1.053P+0.039P2的二次曲线关系；相同孔隙率下不同RMVM的衰减系数在一定范围内分布,即α与P呈带状分布关系,且孔隙率越高带宽越大。通过实验测量得到的衰减系数基本分布在模拟数据带内,说明基于RMVM的模拟计算具有可行性。此外,根据模拟结果初步探究了孔隙数量、面积、宽度、高度等形貌参量对衰减系数的影响。本文建立的RMVM可以真实地描述CFRP中孔隙形貌的复杂性和随机性,为澄清孔隙导致的超声波散射衰减机理提供了很好的模型基础。
[Abstract]:Ultrasonic testing of carbon Fibre Reinforced plastics (CFRP) porosity is one of the hot topics in the field of nondestructive testing, in which ultrasonic attenuation method is the most widely used.The theoretical models of this method mainly include regular pore model and random Void model. The former assumes that the pore is a regular geometric shape, and follows a fixed distribution function, which is different from the actual pore morphology.There is a big deviation between the theoretical results and the experimental results, the latter takes the pore complexity and random morphology into account, and the deviation between the theoretical results and the experimental results is obviously reduced.However, there are still differences between the pore morphology and the actual pore morphology based on mathematical method, and the modeling effect is not ideal when the pore size dispersion degree in the sample is large.In order to describe CFRP pore morphology more realistically and accurately, this paper proposes to study the complex relationship between CFRP porosity, pore morphology and ultrasonic attenuation coefficient by establishing a real morphology pore model, Real Morphology Void Model (RMVM).One-way CFRP laminates prepared from 16 layers of prepreg were studied. 441 CFRP metallographic photographs were obtained by serial slice method. The real pore morphology was extracted in situ by median filter and binarization image processing methods.To establish RMVM with porosity ranging from 0.58% to 3.49%.The finite difference time-domain (FDTD) method is used to simulate the RMVM, and the statistical results of the attenuation coefficient 伪 -porosity P are obtained.The results show that 伪 increases with the increase of P, and they are conic of 伪 0.9051.053P 0.039P2, and the attenuation coefficients of different RMVM are distributed in a certain range under the same porosity, that is, 伪 and P show a zonal distribution relationship, and the higher the porosity, the larger the bandwidth.The attenuation coefficient obtained by the experimental measurement is basically distributed in the simulated data band, which shows that the simulation calculation based on RMVM is feasible.In addition, based on the simulation results, the effects of the number of pores, area, width and height on the attenuation coefficient are preliminarily investigated.The RMVM established in this paper can describe the complexity and randomness of pore morphology in CFRP and provide a good model basis for clarifying the attenuation mechanism of ultrasonic scattering induced by pores.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33;TB302.5

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