Health monitoring of sandwich composites with auxetic core subjected to indentation tests using acoustic emission

The quasi-static indentation behavior of an eco-sandwich composite with auxetic core consisting of polylactic acid reinforced with flax fibers will be discussed in this article. The structures involved in the test were manufactured using 3D printing technique. Four configurations with different number of cells in the core, were tested. It is found that sandwiches with high number of cells are stiffer and dissipate more energy. Experimental tests were monitored with acoustic emission technique in order to detect the appearance and the evolution of damage behavior. An unsupervised pattern recognition algorithm was used to post process the acoustic emission signals. The classification is conducted using k-means algorithm. Results show that there are three different classes of events for each configuration, which are the core cracking, the matrix cracking and the fiber/matrix debonding. The evaluation of the contribution of each damage mechanism on the total amount of failure was deduced according to the amplitude range, the cumulative number of hits and the acoustic energy activity. Furthermore, macroscopic and microscopic observations were performed in order to correlate acoustic emission classes with the damage mechanisms observed.

Automated summary

This article discusses the quasi-static indentation behavior of an eco-sandwich composite with an auxetic core, finding that sandwiches with a higher number of cells are stiffer and dissipate more energy. Experimental tests were monitored using acoustic emission technique and an unsupervised pattern recognition algorithm was employed for post-processing. The contribution of each damage mechanism was evaluated based on amplitude range, cumulative number of hits, and acoustic energy activity, with macroscopic and microscopic observations used to correlate acoustic emission classes with observed damage mechanisms.