To protect the undercarriage of a railway vehicle moving at high speeds, rolling stock manufacturers use shields made of polymer composites. During operations, damage to these guards is often observed due to railway ballast hitting them. Verification of the course of the impact and the extent of damage caused to these shields has drawn attention to the potential effect of the structural damping of the material on the impact resistance of these shields. This property is expressed by the coefficient of restitution, which determines the amount of energy absorbed by the material during the impact, and its direct influence on the simulation results is rarely a separate research subject. In this paper, an attempt was made to verify the influence of this coefficient on the compliance of railway ballast impact simulation results with the results of bench tests. Two test stand were built for this purpose: to measure the coefficient of restitution of the composite samples and to verify the impact resistance of shields The principle of the restitution coefficient tester is based on the ISO 10545-5 standard and its operation is based on measuring the time elapsed between two consecutive impacts of a steel ball on the surface of the tested specimen. The experimental tests carried out led to the determination of the coefficient for the composite material adopted. This material was a laminate of flax fibres and epoxy resin with a core of 2 different types of materials, i.e., XPS and EPS, and the coefficient values obtained were 0.74 and 0.69 respectively. Knowing these values allowed us to relate the extent of damage caused to the value of the restitution coefficient. To simulate the impact of the railway ballast on the casing, a second test bench was prepared, which allowed the impact to be reproduced. The observed significant effect of restitution coefficient on the results confirmed the validity of the assumption.