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Description
Bio-inspired composite architectures offer promising strategies to achieve a favourable trade-off between stiffness and energy absorption in engineered materials. Bone represents a paradigmatic example, where hierarchical organization and compliant–stiff interfaces contribute to complex deformation mechanisms under mechanical loading. In this work, the mechanical role of stiff interlayers (inspired by the cement line) and deformable cores was systematically investigated under flexural loading. Samples were fabricated using PolyJet multi-material 3D printing providing a controlled experimental platform. A set of layered and sandwich architectures was designed by combining glassy and rubber-like photopolymers with well-defined interfaces, enabling a rigorous analysis of the influence of interlayer position on flexural deformation modes considering both stiff and compliant matrices.
The results reveal that the placement of stiff interlayers strongly modulates the flexural response, highlighting a non-trivial interplay between layer position and bending-induced shear deformation. The introduction of a soft core significantly enhanced the energy absorbed at peak load compared to the single constituents, while preserving structural integrity. In particular, the best-performing configuration with a soft core absorbed approximately twice the energy absorbed by the monolithic samples built with the stiffest and strongest available material. Hybrid architectures combining interlayers and core–shell configurations further improved mechanical performance by promoting enhanced stress redistribution and deformation mechanisms.
Overall, this study provides design guidelines for layered composite architectures that balance stiffness and energy absorption through the combined effects of material contrast and interface placement, while offering insights into the potential mechanical implications of hard cement lines on the flexural behavior of trabecular bone.