Abstract—A method for measuring the acoustic impedance for the assessment of the porosity of carbon fiber reinforced plastic composites using laser thermo-optical excitation of longitudinal acoustic waves is proposed and experimentally realized. The acoustic impedance of the test sample is measured from the magnitude of the antiderivative ultrasonic pulse reflected from the immersion liquid–sample interface. A method for calculating the porosity of carbon fiber plastic composites based on the measured acoustic impedance is presented. Composite samples with three different carbon fiber layers stacking schemes were investigated. It is shown that in the studied composites, the local porosity distribution is nonuniform along the fiber stacking plane. The porosity value, averaged from optoacoustic measurement results, actually coincides with X-ray tomography data within the error limits. The presented method for determining porosity does not require determining the volume and mass of the studied object and can be used for investigation of composite structures with complex shapes.

中文翻译：

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基于声阻抗测量的碳纤维增强塑料复合材料定量孔隙率评估的激光光声法

摘要提出并通过实验实现了一种测量声阻抗的方法，该方法利用纵向声波的激光热光激发来评估碳纤维增强塑料复合材料的孔隙率。根据浸没液体-样品界面反射的反导超声脉冲的幅度来测量测试样品的声阻抗。提出了一种基于测得的声阻抗计算碳纤维塑料复合材料孔隙率的方法。研究了具有三种不同碳纤维层堆叠方案的复合材料样品。结果表明，在所研究的复合材料中，沿纤维堆积平面的局部孔隙率分布不均匀。根据光声测量结果求出的孔隙率平均值，实际上与误差范围内的X射线断层扫描数据重合。所提出的确定孔隙率的方法不需要确定研究对象的体积和质量，并且可以用于研究具有复杂形状的复合结构。