The TAPPI T 818 standard specifies a method for measuring the annular compressive strength of Cardboard using the flexible beam method. Annular compressive strength refers to the maximum pressure that Cardboard can withstand when the edge is compressed until it crumbles under the condition of an annular specimen. It is an important indicator to measure the compressive performance of Cardboard. This method is suitable for Cardboard with a thickness of 0.280.51mm, and the test results can be used to evaluate the compressive performance of Cardboard in scenarios such as Encasement and transportation. Through this standard, paper and Encasement companies can accurately evaluate the mass and applicability of Cardboard, optimize the production process, and ensure that the product performance meets the requirements.