基于随机孔隙模型的CFRP孔隙率超声检测研究

Investigations on CFRP Porosity by Using Ultrasonic Testing Based on Random Pores Model

为解决碳纤维增强复合材料(Carbon fiber reinforced plastics,CFRP)孔隙率超声衰减法检测中,理论值与试验值存在差异的问题,基于随机介质理论,建立CFRP孔隙特征的数学描述方法。该方法利用极值搜索法对椭圆形自相关函数随机介质构造方法进行改造。通过正交试验分析各构造参数对随机孔隙构造结果的影响,并利用CFRP试样的大量孔隙形态及分布统计数据,对自相关长度ab、自相关长度比r0=a/b及分区边长D等参数进行优化,最终构建CFRP随机孔隙模型。研究发现,随机孔隙模型能够反映孔隙的形貌及分布等随机特征,为研究CFRP孔隙对超声波的散射作用提供理论依据。根据此模型计算出的超声衰减系数与孔隙率对应关系与试验结果之间规律一致。表明该随机孔隙模型能够很好地表征CFRP的整体弹性性能及由随机孔隙引起的局部弹性微扰。

In order to solve the problem that there are differences between the analytical and experimental results of ultrasonic testing of carbon fiber reinforced plastics（CFRP） porosity by using ultrasonic attenuation method,a mathematical characterization for pores in CFRP is proposed on the basis of random medium theory.Random medium with ellipsoidal autocorrelation functions is improved through minimum searching method.The effects of building parameters are found with orthogonal test.And parameters such as autocorrelation length a and b,ratio of autocorrelation length r0=a/b and side length of sub-zone D,are optimized according to a large number of CFRP pores morphology and distribution statistical data.Finally,random pores model for CFRP is established.The results show that the morphology and distribution of pores can be characterized by random pores model based on actual statistical data of pores,which provides the theoretical foundations for the analysis of ultrasonic scattering from CFRP pores.For the relation between ultrasonic attenuation coefficient and porosity,the result of numerical calculation accords with that of experimental test.The result shows that random pores model can characterize global elastic properties and partial elastic disturbance from random pores of CFRP.