Nonlinear ultrasonic techniques rely on the measurement of nonlinear elastic effects caused by the interaction of ultrasonic waves with the material damage, and have shown high sensitivity to detect micro-cracks and defects in the early stages. This paper presents a nonlinear ultrasonic technique, here named nonlinear elastic multi-path reciprocal method, for the identification and localisation of micro-damage in composite laminates. In the proposed methodology, a sparse array of surface bonded ultrasonic transducers is used to measure the second harmonic elastic response associated with the material flaw. A reciprocal relationship of nonlinear elastic parameters evaluated from multiple transmitter-receiver pairs is then applied to locate the micro-damage. Experimental results on a damaged composite panel revealed that an accurate damage localisation was obtained using the normalised second order nonlinear parameter with a high signal-to-noise-ratio (∼11.2 dB), whilst the use of bicoherence coefficient provided high localisation accuracy with a lower signal-to-noise-ratio (∼1.8 dB). The maximum error between the calculated and the real damage location was nearly 13 mm. Unlike traditional linear ultrasonic techniques, the proposed nonlinear elastic multi-path reciprocal method allows detecting material damage on composite materials without a priori knowledge of the ultrasonic wave velocity nor a baseline with the undamaged component.
- Composite materials
- Nonlinear damage localization
- Structural health monitoring (SHM)
ASJC Scopus subject areas
- Acoustics and Ultrasonics
Boccardi, S., Calla, D. B., Ciampa, F., & Meo, M. (2018). Nonlinear elastic multi-path reciprocal method for damage localisation in composite materials. Ultrasonics, 82, 239-245. https://doi.org/10.1016/j.ultras.2017.09.001