Abstract: In this paper, two types of glass fiber reinforced epoxy composites laminated board with unidirectional plate and multidirectional plate are used. The impact test was performed using free fall impact testing machine. Digital microscope was used to describe the damage morphology. By introducing factor K and establishing a quantitative relationship between the different impact energies and the pit depth, the relationship and the impact damage morphology characteristics under different impact energy are compared. According to the relationship between the depth of the pit and the factor K, the energy value of the impact is measured by measuring the pit depth. According to the impact energy value, the damage of the structure can be judged by experience.

Key words: low-energy impact, external surface damage, feature description, depth of pit, quantitative relation, relational factor