Sound Transmission Loss and Compression Properties of Sandwich Panels with Milli-perforated Honeycomb Core

In this study, an impedance tube test was conducted to investigate low frequency sound transmission loss (STL) of a sandwich panel with milli-perforated honeycomb core. Three different configurations of perforated honeycomb cores with 3 mm diameter orifices are explored: (1) a global spiral, (2) four orifices per cell, and (3) six orifices per cell. It is found that the 3D-printed PLA honeycomb sandwich panel shows STL values from 34 dB to 59 dB within the frequency range of 100–1600 Hz. The spiral configuration outperforms the unmodified sandwich whereas the four and six orifice configurations exhibit higher STL than the spiral for frequencies between 650 Hz and 900 Hz. Moreover, the in-plane and out-of-plane compression tests were performed to determine the effect of having milli-orifices on the mechanical properties of the honeycomb core. It is concluded that the milli-perforated honeycomb core has the potential to produce a lighter multifunctional honeycomb sandwich panel with enhanced low frequency STL without a significant degradation in in-plane compression properties.