Effect of thickness variation on impact damage characteristics of indicative coatings

This study investigated an epoxy indicative coating designed to reveal the degree of damage through changes in its cracking characteristics after low-energy impact. Thickness was a critical factor in the pattern of crack extension and distribution of the indicative coating upon impact. Therefore, experiments and finite element analysis were used to reveal the correspondence between epoxy coating (EC) thickness and the damage indications in terms of the number of cracks, the direct cracking area, and the energy absorption-to-mass ratio. Results showed that EC of different thicknesses from 0.5 to 1.0 mm all had the function of indicating damage. The number of cracks and the direct cracking area both increased with impact energy from 1.0 to 3.0 J. The former was relatively independent of coating thickness, whereas the latter was largely influenced. Meanwhile, the coating’s ability to absorb energy also enhanced with its thickness. However, if the effects of weight increase and crack clarity were taken into account, a suitable coating thickness should be selected. For instance, in this study, the 0.8 mm EC achieved an energy consumption effect close to the 1.0 mm EC, but with a lower weight, as well as better regularity and clarity in its crack distribution.