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A novel superposed waveform method for damage detection of composite laminates

Abstract A novel vibration testing method using a superposed waveform method (SWM) is proposed as a fast, easy and universal vibration-based technique for damage detection in structures. This method can be carried out conveniently over arbitrary frequency bands, especially in high-frequency ranges, which are more sensitive to small damages or defects, but are less convenient to use in general testing methods compared to low-frequency ranges. Unlike most published traditional vibration-based methods used to directly obtain mode shapes or operational deflection shapes (ODSs), the SWM presented in this paper calculates vibration parameters using propagating waves in structures. A comparison of natural frequencies and mode shapes of a cantilever obtained by the traditional vibration method and SWM validates the reliability of the SWM. We used the SWM to locate impact damage in composite laminates as proof-of-concept application. A set of piezoceramic transducer patches acted as actuators on composite laminates damaged by low velocity impact; propagating wave data were acquired by a scanning laser Doppler vibrometer. A modified signal actuated the propagating wave, which was used to calculate the frequency response functions and the ODSs at each frequency using the SWM. The mode shapes of high-frequency resonance clearly showed the damaged area, and the local resonance of damage was tested using the ODS of laminate at a certain frequency to identify the damage location. The SWM proposed in this paper enables efficient and effective vibration measurements, especially at high frequencies, and can be used to detect damage in composite laminates.