Nanolayer coextrusion allows processing films composed of thousands of layers of alternating polymers with individual layer thicknesses below 100 nm [1]. It has been observed that below a critical layer thickness (around 10 nm for PS/PMMA nanolayered systems), the layers tend to lose their integrity, i.e. they break spontaneously during the process [2]. These layer break-ups have been attributed to small interfacial perturbations that are amplified by van der Waals forces [2]. To confirm this hypothesis, an experimental setup was designed to follow in situ the dewetting of a trilayer system (thin PS film sandwiched between two thicker PMMA films) using an optical microscope and a hot stage, under static conditions (no external force) [3]. In this study, we aim at investigating the effect of a shear flow on the dewetting kinetics using both experimental and numerical approaches. The results suggest that shearing during the flow in process acts as a stabilizing factor and tends to delay or suppress the appearance of layer breakups. References. 1. M. Ponting, A. Hiltner, E. Baer Macromol. Symp. 2010, 294, 19 2. A. Bironeau, T. Salez, G. Miquelard-Garnier, C. Sollogoub, Macromolecules, 2017, 50, 4064 3. M.S. Chebil, J.D. McGraw, T. Salez, C. Sollogoub and G. Miquelard-Garnier, Soft matter 2018, 14 (30), 6256