Effect of static ageing on the vibration behavior of synthetic and bio-based composites

The assessment of damage in composite materials remains a major challenge, particularly due to the complexity of their dynamic behavior under mechanical loading. The evolution of the vibrational properties of laminated and sandwich composites, influenced by damage induced by static loading, requires a thorough understanding. This article examines the effect of stacking sequence in laminates, the nature of the constituents, and damage on the vibrational properties of laminated and sandwich structures. Free vibration flexural tests were conducted on bio-based and synthetic composites, both manufactured by contact molding. Different configurations were studied to analyse their influence on the vibrational response before and after damage under static loading. The main results show that damage leads to a decrease in resonance frequencies, indicating a loss of material stiffness. Conversely, the damping factor increases with damage severity, a behavior strongly influenced by the stacking configuration and the nature of the composite constituents. These observations can be explained by energy dissipation mechanisms related to the viscoelastic nature of composites and the redistribution of internal stresses in the presence of defects.