Acoustic Emission and Ultrasound Phased Array Techniques for Composite Material Evaluation

The successful application of various acoustic evaluation techniques to composite materials and structures depends on the understanding of the acoustic wave propagation mechanisms. However, due to the anisotropic nature of composite materials, where the acoustic signal velocity and attenuation depend on its traveling direction, the correlation of the different material failure modes to the recorded acoustic signals, such as during of an acoustic emission (AE) inspection, is difficult to be defined. This issue becomes even more challenging for ultrasound phased array technique, where unlike a conventional ultrasound single element transducer, an ultrasound phased array of sensors will generate and receive acoustic energy at various desired directions and locations. Such heightened flexibility and sensitivity is essential for the complex shape of modern composite structures. In this paper, the influence of fiber orientation on AE signal was first studied. AE parameters such as counts, duration, energy, rise time and amplitude for aluminum and composite plate were analyzed in MS-Excel and results were compared to AE software. Acoustic velocities along various fiber directions were also theoretically studied and experimentally measured. Then ultrasound phased array technique and related parameters such as ultrasound beam angle and focusing, frequency and material attenuation factors were quantitatively analyzed, and the optimization and limitation of ultrasound phased array inspection procedure were summarized.