Microstructural characteristics and its role in load transfer within staggered architectures of brittle and compliant constituents

Many biological composites rely on interlocking arrangements of brittle (hard) and compliant (soft) constituents, which give rise to diverse load-transfer pathways and, in turn, exceptional resistance to mechanical loading, enhanced crack suppression, and effective energy dissipation under dynamic conditions. In this study, we develop a micromechanical model to explain how microstructural characteristics and mechanical properties of constituents govern the overall deformation of staggered composites. Our analysis examines how platelet (inclusion) geometry, arrangement, and packing density influence load transfer. We find that the size of staggered regions and packing density play more dominant roles than the platelet volume fraction in controlling the elastic moduli and nonlinear inelastic tensile response of the staggered composites. Furthermore, we identify design pathways for achieving high elastic stiffness in composites with low packing density and low platelet volume fraction by increasing the extent of staggered regions and forming connected platelet networks. A noteworthy and somewhat counterintuitive result is that platelet volume fraction has a minor effect on mechanical behavior in staggered architectures, in contrast to non-staggered microstructures, because staggered layouts activate multiple load-transfer mechanisms enabled by tailored platelet geometry and arrangement. We validate the prediction of our mechanical models against experimental data and other models.