▎ 摘　　要

Exploring and understanding the structure-mechanical property relations in hierarchical graphene assemblies is crucial for optimizing their mechanical properties and developing new functionalities, as the tensile strength is two orders of magnitude degradation from pristine graphene to graphene assemblies. Yet, quantifying the strength degradation across multiscale is a challenge due to the complex hierarchical structures. Thus, key structures and dominated factors at different lengthscales that affect the mechanical properties of graphene assemblies should be extracted for the reasonable unveiling of this problem. In this study, the multiscale mechanical degradation of graphene assemblies through practical microstructure-guided multiscale modeling is characterized. Combining with experimental observations, three representative models are developed to study the mechanical behaviors of graphene assemblies at different lengthscales. Then, the dominated factors affecting the strength at these lengthscales are identified, that is the defects in monolayer graphene, tension-shear load transfer for stacked graphene, and uniformity of graphene assemblies. Based on the simulation results, the structure-strength relation of graphene assemblies is given, and practical strategies are proposed followed by experimental realization, to significantly improve the mechanical properties of graphene-based nanocomposites.