Researchers from the Beckman Institute for Advanced Science and Technology have created a 3D vascular system that allows high-performance composite materials like fibreglass to heal autonomously, and repeatedly.
Internal damage in fibre-reinforced composite materials is sometimes very difficult to detect and nearly impossible to repair using conventional methods. A small internal crack can quickly grow into de-lamination where the layers can separate, this remains one of the most significant factors limiting more widespread use of composite materials.
Led by professors Nancy Sottos, Scott White, and Jeff Moore, the team at Beckman created 3D vascular networks—patterns of microchannels filled with healing chemistries—that thread through a fibre-reinforced composite. When damage occurs, the networks within the material break apart and allow the healing chemistries to mix and polymerise, autonomously healing the material, over multiple cycles.
Scott White, aerospace engineering professor and co-corresponding author said;
This is the first demonstration of repeated healing in a fiber-reinforced composite system, Self-healing has been done before in polymers with different techniques and networks, but they couldn’t be translated to fiber-reinforced composites. The missing link was the development of the vascularisation technique.
The vasculature within the system integrates dual networks that are isolated from one other. An epoxy resin and hardener are sequestered in two different microchannel networks. When a fracture occurs this ruptures the separate networks of healing agents, automatically releasing them into the crack, like a bleeding cut. As they come into contact with one another in situ, or within the material, they polymerize to essentially form a structural glue in the damage zone. The team has tested this over multiple cycles and all cracks healed successfully at nearly 100 percent efficiency.
The vascular networks within the structure are not straight lines. In order for the healing agents to combine effectively after being released within the crack, the vessels were overlapped to further promote mixing of the liquids, which both have a consistency similar to maple syrup.