Smart multiphase composite materials that repair themselves by a release of liquids that become solids

The subject of this research in fracture mechanics is the enhancement of flexural toughening beyond the original hardened material by the release of liquid `healing' chemicals such as adhesives from hollow fibers into cementitious matrices in response to loading. These chemicals solidify in the cracks to impart an increased toughness and ductility. The mechanisms appear to be adhesive rebonding of the fibers and crack-filling with adhesives that behave more rigidly when bonded inside cracks. An investigation was made into the development of smart cement composites that can self-repair internal cracks due to mechanical loading. The research focused on the cracking of hollow repair fibers dispersed in a composite and the resulting timed release of chemicals that seal matrix microcracks and rebond any damaged interfaces between fiber and matrix. Fiber pull-out tests were performed to examine rebonding of fibers. The rebonding was successful.