This standard specifies an important test method for determining the ability of plastic materials to resist crack propagation under repeated tensile loads. It is primarily applicable to rigid and semi-rigid thermoplastics and thermosetting plastics, including composites reinforced with short fibers. The core of the method involves applying a constant-amplitude cyclic tensile load to a pre-prepared specimen with a sharp notch, and measuring the growth of the crack length with the number of load cycles in real-time or intermittently using specialized equipment (such as a dynamic fatigue testing machine equipped with corresponding fixtures and software). Based on linear elastic fracture mechanics theory, the method ultimately transforms experimental data into a key curve describing the material's resistance to fatigue crack propagation—namely, the relationship between crack propagation rate and the stress intensity factor range or energy release rate range. This provides a scientific basis for material selection, life prediction, and quality control.