Air damping influence on dynamic parameters of laminated composite plates

• Dynamic parameters are burdened with the measurement error due to air damping.
• The air damping has significant influence mostly on modal loss factors.
• A vacuum chamber should be provided if dynamic parameters of plates are studied.

Damping performance of lightweight composite structures, like fibre reinforced plastics (FRPs) is more efficient than the conventional materials. This phenomena was found valuable in the aerospace and transport industries. For this reason accurate material properties of FRPs are required for precise prediction of dynamic response. However, the given properties are often burden with a significant uncertainty level due to environment influence which includes air damping, temperature changes, humidity, etc. The present study concerns with the air damping influence on the dynamic behaviour of laminated composites plates with moderate damping level. The effect on dynamic characteristics is evaluated experimentally using a vacuum chamber and a laser vibrometer. Resonant frequencies and modal loss factors changes are investigated in terms of material type, sample size and excitation amplitude. A semi-automatic and time efficient two-step testing procedure is developed for a precise measurement of loss factors of laminated composite plates.