Strong Interfaces Enable Efficient Load Transfer for Strong, Tough, and Impact-Resistant Hydrogel Composites.

Many biological hydrogels are mechanically robust to bear quasi-static and impact loads. In contrast, the mechanical properties of synthetic hydrogels against impact loads remain substantially unexplored, albeit their mechanical robustness under quasi-static loads has been extensively developed. Here, we report on the design and synthesis of strong, tough, and impact-resistant hydrogel composites by reinforcing Ca-alginate/polyacrylamide hydrogels with glass fabrics and conferring strong interfaces between the hydrogel matrix and the fibers. The fabric enables high elastic modulus, the hydrogel matrix enables large dissipation, and the strong interfaces enable efficient load transfer for synergistic strengthening and toughening, which is manifested by digital image correlation analyses. Under quasi-static loads, the hydrogel composite exhibits an elastic modulus of 35 MPa and a toughness of 206.7 kJ/m 2 . Under impact loads, a piece of 7.7 g sample bears the impact of energy of 7.4 J and resists more than 100 cycles of consecutive impact of 600 mJ. As a proof-of-concept, a hydrogel composite as a safeguard to protect fragile glasses from impact is demonstrated. Because impact phenomena are universal, it is expected that the study on the impact of hydrogels will draw increasing attention.