不同厚度碳纤维布/环氧树脂复合材料孔隙率超声衰减模型

复合材料中孔隙的存在造成了材料性能的下降,因此,对材料孔隙的检测至关重要。本文利用异丙醇(IPA)添加量的不同,制备了不同层数、不同孔隙率含量的碳纤维(CF)布/环氧树脂层合板试件。采用脉冲反射法测试计算了CF布/环氧树脂层合板试件的超声衰减系数,通过金相显微分析对孔隙的分布、形状及尺寸进行了表征,运用MATLAB对金相显微图进行分析得到试件的孔隙率。讨论了孔隙率对材料的声速、声阻抗及超声衰减系数的影响规律,利用4组不同层数样本试件的孔隙率和超声衰减量的试验数据,给出了基于模型的孔隙率与材料层数、超声衰减量的拟合公式。结果表明,随着IPA添加量的增加, CF布/环氧树脂层合板(2 mm)孔隙率从1.09%增加到4.16%,材料的声速和声阻抗均下降,超声衰减系数从2.51 dB/mm增大到5.34 dB/mm。孔隙率为1%时,厚度从2 mm (8层)增加到5 mm(20层),衰减系数增大了0.54 dB/mm。

Ultrasonic attenuation model of porosity of carbon fiber cloth/epoxy resin composites with different thicknesses

The presence of pores in composites results in a decrease of material properties, therefore, it is critical to the detection of material pores. Carbon fiber (CF) cloth/epoxy resin laminated plates with different number of layers and different porosities were prepared by using different amounts of isopropanol(IPA). The ultrasonic attenuation coefficient of the test piece was calculated by pulse reflection method. The distribution, shape and size of the pore were characterized by metallographic microscopic analysis. The porosity of the test piece was obtained by analyzing the metallographic micrograph by MATLAB. The effects of porosity on the sound velocity, sound impedance and ultrasonic attenuation coefficient of the CF/epoxy resin laminated plates were discussed, and the fitting formulas of porosity, material layer number and ultrasonic attenuation were given based on the experimental data of porosity and ultrasonic attenuation of four samples with different layers. The results show that as the amount of IPA increases, the porosity of the laminate (2 mm) increases from 1.09% to 4.16%, the sound velocity and acoustic impedance of the material decrease, and the ultrasonic attenuation coefficient increases from 2.51 dB/mm to 5.34 dB/mm. When the porosity is 1%, the thickness increases from 2 mm (8 layers) to 5 mm (20 layers), and the attenuation coefficient increases by 0.54 dB/mm.