Tough, Ductile, and Strong Hard‐Soft Cementitious Composite Enabled by Multi‐Material Additive Manufacturing

Abstract

ABSTRACT Monolithic cementitious materials lack fracture resistance and are brittle. Advancements in additive manufacturing techniques with cement‐based materials and architected designs have remained limited to the use of a single (cement‐based) constituent. This work charts a new pathway for manufacturing and designing tough, ductile, and strong architected cement‐based composites by proposing a novel multi‐material additive manufacturing (MMAM) technique for the first time, integrated with a coupled experimental‐numerical design approach. The new class of architected cementitious composites (ACC) of mortars and elastomeric constituents (silicone and polyurethane) are exemplified, through a layered hard‐soft architected design, inspired by the microstructure of a sea sponge (glass sponge Euplectella aspergillum ). The MMAM technique alternates extrusion of hard‐soft composites, enabling systematic control over the geometry and constituents of resulting architected structures. The results demonstrate layered mortar‐silicone composites achieved up to 3.9‐ and 8.8‐fold enhancements in fracture toughness and up to 11.7‐ and 12.4‐fold enhancements in ductility relative to monolithic 3D‐printed (3DP) and cast mortars, respectively. A coupled large‐deformation phase‐field–cohesive‐zone (PF‐CZM) framework was used to systematically probe soft‐layer thickness and bulk soft‐material properties. Simulations revealed that combining higher‐stiffness soft layers with reduced thickness can yield up to a 24‐fold increase in work‐of‐fracture while recovering the load‐bearing capacity of monolithic mortar. Guided by numerical predictions, experiments on thin, stiffer polyurethane interlayers validated the numerical predictions and provided additional experimental evidence that the proposed (mortar‐polyurethane) composites achieve 82‐ and 187‐fold higher fracture toughness, and 22.6‐fold higher ductility, relative to 3DP and cast monolithic references while recovering the flexural strength to levels statistically comparable to monolithic mortar. These large gains arise from three synergistic mechanisms: crack arrest/deflection, crack bridging, and discontinuous layerwise crack re‐nucleation, activated by the layered hard‐soft architecture and supported by DIC/AE fracture analyses). The proposed MMAM‐enabled fabrication‐design‐mechanics approach in ACC can unleash entirely new pathways for engineering next‐generation damage‐resilient and multi‐functional concrete structures.