Damage assessment in composite materials using full wavefield analysis

WANDOWSKI, Tomasz, Pawel H. MALINOWSKI, and Wieslaw M. OSTACHOWICZ. "Damage assessment in composite materials using full wavefield analysis." see http://www.ndt.net/article/aero2017/papers/NDT2017-014_Damage_assessment_in_composite_materials_using_full_wavefield_analysis.pdf

Abstract 

In this paper damage assessment method is presented. This method is based on phenomenon of guided elastic waves propagation. Guided waves are generated by piezoelectric transducer and registered by Scanning Laser Doppler Vibrometer (SLDV). Signal processing is based on the analysis of full wave-field measurements. In this approach guided wave signals are gathered from dense mesh of measurement points spanned over investigated area of investigated structure. This approach allows to create animations representing the guided wave propagation which are suitable for analysis of interaction of guided waves with different discontinuities located in composite material. In the research attention is especially focused on analysis of phenomenon of guided wave mode conversion. This phenomenon occurs due to the interaction of guided wave with discontinuities in the structure. Guided wave mode conversion phenomenon has potential for damage detection. Method is validated for the fibre reinforced composite materials. In the research such discontinuities like delamination simulated by teflon insert with different shapes and location as well as true delamination created by impact are investigated. In the research auxiliary nondestructive testing (NDT) method is utilized. The aim of this method is to indicate the depth of discontinuity, and to prove that delamination was created. Auxiliary method is based on terahertz spectroscopy (THz). This method is based on analysis of propagation of electromagnetic waves in the terahertz band. THz spectroscopy method can be utilized for damage assessment in the materials that do not conduct electric current. 

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