GB/T 45877-2025 "Carbon Fiber Composites — Test Method for In-Plane Biaxial Tension of Laminates" is a national standard used to guide the in-plane biaxial tension testing of carbon fiber composite laminates. It systematically specifies the principles of the test, required equipment and instruments, specimen specifications, test conditions, detailed procedures, data processing, and report preparation. This standard is primarily applicable for evaluating the mechanical properties of 0/90 orthogonal ply laminates under complex stress states. The core testing instruments involved in the test include a biaxial tensile testing machine, extensometers or strain gauges for measuring deformation, and a data acquisition system to ensure accurate bidirectional mechanical performance data.