Effect of glass fiber and polyester thickness on the ballistic velocity limit of glass fiber reinforced plastics

Glass fiber reinforced plastics (GFRPs) is a key material for the outer protecting layer of ships as well as for energy storage tanks. Its ballistic and blast resistance is closely related to the inclusion structure of its glass fiber and polyester matrix, however, the related detailed studies have not been reported. In this paper, ballistic shooting tests and finite element simulations are both employed to investigate the ballistic limit velocities (V50) of GFRPs and reveal the effects of glass fiber layers and the polyester matrix thickness on the V50. The results show that the V50 of GFRPs is essentially linearly related to the thickness of the target plate for a given number of glass fiber layers. An increase in the number of glass fiber layers enhances the overall V50 value of GFRPs, but the linear relationship with the thickness remains unchanged. The target plate with more layers of glass fiber interacts with the projectile for a longer time, resulting in the debonding of the fiber and the resin matrix. The resin around the crater loses its support and then produces irregular cracks. Based on energy conservation, a theoretical model for predicting the V50 of GFRPs with considering the effects of glass fiber and polyester matrix is proposed. After comparing the results of theoretical calculations with experimental and simulation data, the relationship equations between the key parameters (ballistic strength) in the model and the number of fiber layers and target plate thickness are finally given. These findings can provide support for the design of ballistic GFRPs.