Vibro-impact response of FRP sandwich plates with a foam core reinforced by chopped fiber rods

In the present study, both the impact and vibration response characteristics of fiber reinforced polymer (FRP) sandwich plates (FRPSPs) with a foam core (FC) reinforced by chopped fiber rods (CFRs) are investigated. Initially, a dynamic model is proposed to predict the vibro-impact characteristics of the FC-CFRs-FRPSP structures. Here, by considering the influence of the dispersion pattern of chopped fiber rods, the equivalent material parameters of this complex core are redefined. Also, by employing the modified mid-plane displacement equation based on the principle of virtual work at the impact point, together with the progressive quasi-static approach and Reddy's high-order shear deformation principle, the key parameters such as impact contact force and displacement related to each failure event are obtained. In addition, with consideration of the impact damage, the natural frequencies and vibration responses are solved by using the energy principle, the proportional damping method, and the Duhamel integral technique. Finally, a number of the FC-FRPSP specimens with and without reinforcement of CFRs are fabricated and tested under different impact energies for verifying the present model. Also, the influences of critical geometric and material parameters on the vibro-impact response of the FC-CFRs-FRPSP structures are discussed. It has been found that the FC-CFRs-FRPSP specimens have a smaller vibro-impact response compared to the specimens without CFRs. For example, when impact energy of 10 J is applied, the impact peak force increases by 19.1%, the impact displacement reduces by 26.6%, and the maximum time-domain vibration response reduces by 5.8%. To reduce the vibro-impact response of such structures, it is recommended to adopt a large thickness ratio of the CFR reinforced foam core to the overall sandwich plate as well as volume fraction of CFRs to the foam core with a uniform dispersion pattern.