Abstract: Due to the advantages of high strength and good fatigue strength, composites are widely used in aerospace field. However, voids are easily produced in the preparation process, and it significantly decreased the materials′ final mechanical properties. This paper proposes a composite pore content ultrasonic parameter evaluation method, which works through the measurement of ultrasonic relative nonlinear coefficient, and comparative study sound velocity and acoustic attenuation measurement, set up internal relation of composite pore defects and various parameters and evaluation method. The experimental results show that the relative nonlinear coefficient, velocity of sound and acoustic attenuation coefficient can evaluate composite pore content. Among them, the sound velocity can quickly reflect the density of composite materials. The sound attenuation coefficient within the scope of a certain size can be used as more accurate evaluation. For the samples that the change of sound velocity and acoustic attenuation coefficient is not obvious, using ultrasonic nonlinear coefficient of relative evaluation is more suitable. The study of evaluation for composite pore content provides the reference.

Key words: composite material, ultrasonic testing, pore, multi-parameter