Effect of hybrid composite structure and environmental aging on dynamic properties

Natural fibres, particularly flax, are gaining attention as sustainable alternatives to synthetic reinforcements due to their low density, biodegradability, and reduced environmental impact.Their relatively high damping capacity makes them attractive for vibration-sensitive applications; however, their susceptibility to environmental conditions and lower thermal stability require further investigation.This study examined the effect of laminate configuration and environmental aging on the dynamic behaviour of flax, carbon, and flax-carbon hybrid laminates with a stacking sequence [0/45/-45/90] s.Five configurations were analysed, differing in the placement of carbon layers within the laminate.Specimens were subjected to accelerated aging through thermal shocks and UV radiation.Dynamic tests were performed using an electromagnetic shaker, with frequency ranges selected to capture the first two resonance modes.Measurements were conducted in the initial state and after each aging procedure.The results indicate that the location of carbon plies significantly influences both natural frequencies and vibration amplitudes.Among all configurations, the hybrid configuration with carbon layers at 0° exhibits the highest stiffness -a 36% increase compared to the flax configuration and a 29% increase compared to the carbon configuration.The highest amplitude values were also observed for this hybrid configuration.Environmental exposure generally reduces amplitudes, suggesting changes in effective damping.After both aging processes, a significant decrease in vibration amplitude was observed for all configurations -ranging from approximately 20% to 75%, depending on the laminate configuration and type of aging.In contrast, the effect of aging on beam stiffness is limited; for most configurations, changes in stiffness within the range of ±1-7% were observed.