A non-contact real-time strain measurement and control system for multiaxial cyclic/fatigue tests of polymer materials by digital image correlation method

A non-contact real-time strain measurement and control system based on the Digital Image Correlation Method (DICM), has been successfully established for cyclic/fatigue tests of polymer materials. It allows recording of the evolution of strain during the entire fatigue life of the polymer materials under test. The stress-strain hysteresis loops can also be accurately recorded through synchronizing the stress and strain data. A minimum detectable strain of 0.01% was achieved. In addition, through simplifying the calculation procedure and optimizing the searching algorithm in DICM, a frequency of 10 Hz for strain data acquisition was reached. This made it possible to perform strain-range-controlled fatigue tests on the specimens. The reliability and universality of the system was verified by carrying out different types of multiaxial cyclic/fatigue tests on specimens of an epoxy polymer. The success of this method would facilitate performing various types of fatigue tests on polymer materials and would allow gaining better insight and understanding of their fatigue and failure behavior.