Interpreting the Lempel-Ziv complexity of acoustic emission signals for identifying damage modes in composite materials

Lempel-Ziv (LZ) complexity has been used predominantly in solving the information theoretic problems. However, its application is way beyond information theoretics. It has been used successfully in different biomedical applications. In this research work, this LZ complexity is used for identifying the damage modes in a plain weave fabric carbon fibre-reinforced polymer (CFRP) specimens tested at an elevated temperature. The acoustic signals generated during the tensile test of CFRP specimens at an elevated temperature are recorded. Their LZ complexity values are extracted and compared with different acoustic descriptors. When LZ complexity is used along with peak amplitude of the acoustic signal and its weighted peak frequency, it is able to distinguish the different damage sources of the signal. The acoustic signals with LZ complexity above 0.6 generally indicate their source as delamination or debonding of the fibres in the CFRP specimen. This multiparameter approach is more efficient in distinguishing the different damage modes in the CFRP specimens.