The effect of core height on the vibro-acoustic behavior of fibre reinforced cores

In view of the current state of environmental awareness, the need for reduced emissions and strict government legislation, natural fibre thermoplastic sandwich panels were manufactured using continuous unidirectional and short random flax fibre reinforced polyethylene honeycomb cores. The influence of the reinforcement type in the composite core and of the core height on acoustic property of the panels was investigated using a standing wave apparatus. Measurements were taken in third octave bands in the frequency range from 100Hz to 4kHz. The panels exhibited absorption coefficients of about ~0.5 at higher frequencies and 0.3 at lower frequencies. The absorption at lower frequencies was mainly due to the fibrous arrangement behind the resonating faceplate but at higher frequencies this effect became negligible and the viscoelastic core governed the absorption.