The tensile fracture behavior of thermosetting plastic materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, unsaturated polyester resin (UPR), which is applicable to buffer the vibration and impact properties in rail structure, were used for this investigation. In order to explain a stress-strain behavior of plastic sample, the infrared thermography technique was applied. A high-speed infrared (IR) camera was employed for in-situ monitoring of progressive damages of UPR samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of thermosetting plastic materials during monotonic loadings.