Effects of Z-pins on Lamb waves in composite plates

This experimental research investigates the effects of adding z-pins to a carbon fiber reinforced plate (CFRP) on Lamb wave propagation, such as mode conversion and reflections. The motivation for this study is derived from the current and expected future use of z-pins in aircraft structures coupled with the requirement to design structural health monitoring (SHM) systems for detecting damage in regions of composite structures with z-pins. This experimental study is conducted on two 4.8 mm thick CFRP test articles, where one plate has a 20 by 279 mm2 band of z-pins and the other does not. The z-pins have an average diameter of 0.28 mm and are inserted through the thickness of the panel with an area density of 4% before curing. A three-dimensional (3D) laser Doppler vibrometer (LDV) was employed to collect velocity measurements over a 1 mm uniformly-spaced grid of 17,899 scan points. Time-sequenced 3D LDV scans are presented to show that adding this relatively small amount of z-pins to a 4.8 mm thick CFRP has few measureable effects on Lamb wave propagation.

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