GB/T 31110-2014 "Paper and board — Determination of Z-direction tensile strength" specifies the method for determining the Z-direction tensile strength (internal bond strength) of paper and board. It is applicable to all types of paper and board and is identical to ISO 15754:2004. A specialized peeling test device is used, where the upper and lower surfaces of the specimen are adhered to the test fixtures. The specimen is then stretched at a constant speed until delamination occurs, and the maximum peeling force is recorded to calculate the Z-direction tensile strength. The standard details requirements for specimen preparation, conditioning, fixture parameters, and test speed. The average of multiple measurements is taken as the result to ensure reliable and comparable test outcomes.