Mesoscale crystal plasticity modelling of Cu-Nb nanolaminates composites considering nonlocal effects and confined layer slip mechanisms

• Developed a CLS-nonlocal model integrating nonlocal effects and confined layer slip mechanism for Cu-Nb nanolaminates. • The model effectively captures thickness-dependent strength and strain hardening behavior in nanolaminates • Reducing the layer thickness significantly enhances the strain hardening, which is attributed to GND-induced hardening mechanisms. • The individual contributions of isotropic and kinematic hardening are quantitatively clarified in the Cu-Nb nanolaminates. Nanolaminated materials have garnered considerable attention due to their high strength, elevated strain hardening rate, and measurable plasticity. The heightened strain hardening rate is attributed to the presence of back stress resulting from plastic deformation incompatibility between adjacent lamellae. However, the precise influence of back stress and geometrically necessary dislocations (GNDs) on kinematic hardening and isotropic hardening remains unclear, thereby limiting the understanding of their deformation mechanisms. To address this gap, we employed nanoscale Cu-Nb nanolaminates as a model system and developed a mesoscale plasticity model based on the confined layer slip (CLS) mechanism and the nonlocal effect (referred to as CLS-nonlocal model) of dislocation transport among material points to predict the hardening mechanism of the nanolaminates. By examining the role of GNDs, back stress, and dislocation flux in kinematic and isotropic hardening, the model highlights the influence of layer thickness on strain hardening and mechanical properties. Comparative analyses with the standard crystal plasticity model reveal the CLS-nonlocal model’s superior capability to capture the nuanced mechanical behaviors of nanolaminates, emphasizing its effectiveness in predicting strain hardening phenomena and stress distribution across varied layer thicknesses. This study enriches knowledge by effectively capturing the hardening characteristics of nanolaminates without necessitating the inclusion of explicit grain-dependent terms in the constitutive equations. Moreover, the developed model demonstrates versatility in its applicability to various other types of nanolaminates.