Large Toughening Effect in Biomimetic Geopolymer Composites via Interface Engineered 3D Skeleton

Green and eco-friendly geopolymers with high thermal/acid resistance represent potential candidates for the replacement of traditional Portland cement in construction, as well as many other applications; however, the intrinsic brittleness and low toughness typical of ceramic hinders widespread adoption of this material in various applications. In this work, we fabricated a new type of geopolymer composites by impregnated with interface engineered 3D skeleton resembling the lotus root structure. Highly porous melamine foam was selected as the 3D skeleton and its interior surface was coated with elastomeric polydimethylsiloxane-polyurea block copolymer. Under loading, the interfacial elastomer could deform and absorb large amount of energy concurrently with crack deflection of melamine foam and delamination of interfaces, thus the toughness was substantially improved as results indicated a transition of fracture behavior from brittle failure mode to a more ductile one. With as low as 2.5 wt % elastomer, the fracture toughness and work of fracture were increased by 258% and 654%, respectively. Owing to the three-dimensional reinforcement preform, the issue with dispersion of reinforcing fillers is circumvented. The obtained geopolymer composites with enhanced toughness allow for applications requiring high load capacity. This strategy of manufacturing composites through 3D skeleton opens new pathway to improving mechanical performance of various brittle materials and material processing techniques.