Characterization of surface damage evolution in thin film composite membranes via in situ SEM tensile testing and numerical simulations

Standard mechanical tests fail to predict the functional limits of thin-film composite (TFC) reverse osmosis (RO) membranes. This study utilizes in situ SEM tensile testing to map real-time surface damage evolution. Results reveal a critical decoupling: functional polyamide surface cracking initiates at only 13.9% of fracture displacement, significantly preceding structural backing failure (64.3%). The failure mechanism follows a brittle channel-cracking mode, evolving from nucleation to deep strain localization. These measurable descriptors are used to calibrate a two-step finite element model, establishing a physics-based framework to predict selective-layer surface fracture, which quantitively match experiments and enhance membrane lifetime assessment.