The mechanical durability of paper is a key consideration for applications ranging from shipping boxes to disposable medical substrates. Paper commonly experiences fatigue loading in such applications, but a high-cycle fatigue mechanism has not been identified. This research details paper's high-cycle fatigue degradation mechanism. Paper specimens were loaded with monotonically increasing, constant, and sinusoidally varying cyclic stresses, and the resulting tensile, creep, and fatigue damage accumulation rates were compared. The difficulty in defining the size and growth of cracks in paper's cellulosic fiber network were overcome with optically measured strain fields. We found that fatigue damage can accumulate via a fiber fracture mechanism, while ratchetting, creep, and tensile overload damage accumulation occurs due to failure of inter-fiber bonds. We also discovered the synergistic interaction between creep and high-cycle fatigue damage accumulation mechanisms, which is critical for extending the high-cycle fatigue life of paper.

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