A universal mechanical framework for noncovalent interface in laminated nanocomposites

ZZ He and YB Zhu and HA Wu, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 158, 104560 (2022).

DOI: 10.1016/j.jmps.2021.104560

Owing to the recoverable nature of noncovalent interactions, laminated nanocomposites dominated by noncovalent interfaces can deform inelastically and generate large relative sliding between building bricks under external loading, which not only contributes to outstanding mechanical properties at the macroscale but also induces coordinated deformation behavior over several hierarchical length scales. Nevertheless, it is challenging to develop a universal mechanical approach quantifying such general features given the architecture and noncovalent interface of nonlinear deformation and size effect. Here, we demonstrate that by extending interfacial constitutive relation condensed from various atomic interactions and interlayer configurations, a multiscale analysis framework from bottom-up for brick-interface systems is proposed to decode the interplay between brick deformation and interfacial intrinsic features. Due to the periodicity of interfacial configurations, there are three deformation modes for regular interface under different overlapping lengths, i.e., uniform, localization, and kink, where two critical lengths are defined to generally describe the transformation of deformation modes. The pronounced interfacial kink exhibits multiple topological defects nucleating and propagating across the interface, thereby strengthening and toughening laminated nanocomposites simultaneously. The discrete shear-lag analysis is then performed to evaluate the commensurate versus incommensurate interfacial stacking configurations. We identify that the deformation of commensurate interface behaves similarly to the regular one, while the linear-sliding model can well describe that of incommensurate and random interfaces. Interestingly, we find that counterintuitively, the load transfer capability of an incommensurate interface exceeds that of a commensurate one as the overlapping length is sufficiently long because of resistance to sliding. Our theoretical predictions and the proposed mechanical framework are validated through large-scale molecular dynamics simulations. More importantly, using a few universal characteristic parameters, a deformation-mode phase diagram is proposed to give the landscape for different hierarchical materials with various noncovalent interfaces, providing guidelines for the mechanical design and optimization of brick-interface nanocomposites.

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