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Abstract The solid‐state foaming process produces microcellular foams with an outer layer of solid skin that encapsulates the cellular core. In this article, we implement a 1D model to predict the thickness of the solid skin based on the effectiveT_gof the polymer‐gas system for a given foaming temperature. The model is based on the understanding that bubbles nucleate when the foaming temperature exceeds the effectiveT_gduring the foaming process. The model was validated with experimental results on the PC‐CO₂system, which showed that skin thickness decreases with increased foaming temperature. We also developed a linear correlation to accurately predict effectiveT_gat different CO₂concentrations. The article also explores the model sensitivity to the key input parameters related to gas diffusion. HighlightsLinear correlation to accurately predict effectiveT_gprofiles in PC‐CO₂system.Increasing foaming temperature decreases skin thickness.Model is sensitive to the input parameters related to gas diffusion. 

Abstract The enhanced properties of nanomaterials make them attractive for advanced high‐performance materials, but their role in promoting toughness has been unclear. Fabrication challenges often prevent the proper organization of nanomaterial constituents, and inadequate testing methods have led to a poor knowledge of toughness at small scales. In this work, the individual roles of nanomaterials and nanoarchitecture on toughness are quantified by creating lightweight materials made from helicoidal polymeric nanofibers (nano‐Bouligand). Unidirectional ( = 0°) and nano‐Bouligand beams ( = 2°–90°) are fabricated using two‐photon lithography and are designed in a micro‐single edge notch bend (µ‐SENB) configuration with relative densities between 48% and 81%. Experiments demonstrate two unique toughening mechanisms. First, size‐enhanced ductility of nanoconfined polymer fibers increases specific fracture energy by 70% in the 0° unidirectional beams. Second, nanoscale stiffness heterogeneity created via inter‐layer fiber twisting impedes crack growth and improves absolute fracture energy dissipation by 48% in high‐density nano‐Bouligand materials. This demonstration of size‐enhanced ductility and nanoscale heterogeneity as coexisting toughening mechanisms reveals the capacity for nanoengineered materials to greatly improve mechanical resilience in a new generation of advanced materials.