In Situ Monitoring of Fiber-Reinforced Composites by Markus G. R. Sause

Author:Markus G. R. Sause
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Based on the different ratio of 0° and 90° plies of the four stacking sequences, a different ratio of microscopic failure mechanisms is expected. As seen from Fig. 4.151, qualitatively the total number of signals correlated with matrix cracking increases for an increasing number of 90° plies. Similarly, the absolute number of signals correlated with fiber breakage increases for an increasing number of 0° plies. The absolute number of signals correlated with interfacial failure was found to be similar for all stacking sequences with identical number of 0°/90° interfaces. This type of signals is attributed to the occurrence of inter-ply delamination . The different laminate configurations produce a noticeable change of the cluster positions in the diagrams for each failure mechanism. This is caused by changes of the frequency spectra of the excited Lamb waves and originates from the different elastic properties of the propagation medium and the characteristic depth changes of the acoustic emission sources.

In the following, the pattern recognition results of all specimens are evaluated using the following quantities as introduced in [35, 138, 186]:

The relative number of signals N rel,i and the relative amplitude of signals U rel,i , for the ith of the I tot failure mechanisms with N i of the total signals N tot, are given as

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