In-plane biaxial ratcheting behavior of PVDF UF membrane

A series of in-plane biaxial cyclic tests were conducted to investigate the biaxial ratcheting behavior of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes via cruciform shaped specimens. A tailored biaxial cyclic testing system and an integrated non-contact displacement detecting system were used. The effects of stress amplitude, mean stress, stress rate and constant stress in the Y-direction on ratcheting behavior of PVDF UF membranes in the X-direction were studied. It was found that the ratcheting strain increases more rapidly as stress amplitude and mean stress become larger. However, the ratcheting strain and its rate decreased with increasing the stress rate or the constant stress in the Y-direction. Furthermore, the biaxial ratcheting tests were carried out on PVDF UF membrane with water immersion. It was found that the water immersion environment significantly accelerated the accumulation of ratcheting strain and its rate. (C) 2015 Elsevier Ltd. All rights reserved.