In general, due to the brittle nature of composite materials, there exist many differences in the impact behaviors of metal and composite materials. More specifically, steel components absorb impact energy by plastic deformation while composite materials absorb it by damage mechanism such as fiber debonding, fiber fracture, and matrix cracking. In order to properly use composite materials in industrial applications, the impact property must be well known. In this study, the impact behavior of Sheet Molding Compounds (SMC), which is widely used in industry due to its relative low costs and high productivity, was examined. SMC acts as an elastic material until the applied stress exceeds a certain limit, whereafter the stiffness of the material drastically decreases. In order to conduct impact simulations of SMC flat plates, a modified damage model for SMC was developed and adopted in the user-defined material subroutine of the commercial simulation program LS-DYNA3D. For the sake of effectiveness of impact simulations and consideration of the local stiffness variations, the SMC material property was predicted with consideration of the local differences in fiber volume fraction. Also, an experimental study was carried out by developing a drop weight impact test system. Using this system, the dissipated impact energies of SMC flat plates were measured to investigate the influence of various parameters on the impact behavior. More specifically, drop weight impact tests were conducted by varying the impactor mass, intial velocity, impactor shape, and specimen thickness. The results showed that the specimen thickness variation had the greatest influence on determining the amount of energy dissipation compared to other factors. Thus, in the scope of the current study, it was found that the specimen thickness is the most important parameter that should be considered in the design of SMC components to be used as impact resistance applications. Finally, in order to examine the reliability of the developed impact simulation process, the simulation results were compared to the experimental drop weight test results.
