Case study of the out-of-plane shear strength measurement of paper machine clothing

The press section is essential for paper machine efficiency, and its runnability is connected to the press felt properties. We studied the out-of-plane shear behavior of press felt specimens in both dry and wet conditions. Our strength tester laboratory set-up was modified to simulate pressure pulses in mechanical dewatering in the paper machine. The test arrangement used a moving upper jaw to generate dynamic stress, gluing and a watering system. Draw speeds, length of displacement, number of tensile cycles, and glue type were standardized during the preliminary work. After tests, 45 load-and-unload cycles were plotted in curves, and shear strength and modulus values were calculated. Results show that hysteresis and non-homogenous behavior, drop in maximum forces, and negative load values in the unload direction are connected to the design, density, wetness, fiber entanglement, and intersections of the specimen. The results benefit the work of wet press modeling.