Nondestructive inspection of luxury yacht glass reinforced composite panels by means of transient thermography

Active thermography measurement techniques, based on modulated optical excitation with either reflection or transmission set-up, have been implemented for quantitative assessment of simulated subsurface defects in thick glass reinforced composite laminates employed for luxury yachts construction. The paper investigates detection limits associated to defect’s size, shape and depth as well as recognition of small impact damages over the external gel-coat finishing layer. The obtained results demonstrated the effectiveness of thermal NDE as a powerful and non contact measurement tool for the inspection of large GFRP structures. In particular, results showed that optical lock-in thermography method allows accurate estimation of impact damages (percentage error < 1%), whereas the accuracy of delamination detection and sizing is critically influenced by both defect’s area and shape ratio (l/h), because of multi-dimensional diffusion phenomena.