High-throughput experimental method for measuring fatigue crack growth rate curve of soft materials

The fatigue properties of soft materials, including fatigue crack initiation and propagation, fatigue life and threshold, have been a significant concern in the past few decades. Measuring the fatigue crack growth rate (FCGR) curve is a standard method to characterize fatigue fracture and has been extensively studied in the literature. Conventional methods employing a pure shear configuration measure only one data point on the FCGR curve per test run. Thus, obtaining the whole FCGR curve with numerous data points becomes excessively time-consuming. This work proposes a high-throughput experimental method for measuring the FCGR curve of soft materials. We prepare ten thermoplastic polyurethane (TPU) specimens in single edge notch tensile configuration with different precut crack lengths, use a mechanical mechanism to apply the same cyclic loads to the ten specimens simultaneously, and identify the crack growth of each specimen by image processing. The proposed high-throughput experimental method enables the measurement of over 90 data points on the FCGR curve in a single test run, facilitating the acquisition of the entire curve with just two runs. The obtained FCGR curve exhibits a linear relationship within its middle region on double logarithmic coordinates. The proposed method is further applied to study the effect of temperature on the FCGR curve of TPU specimens. The current experimental setup can be further optimized to accommodate a wider range of soft materials with diverse mechanical properties and specific loading conditions.