Self-repairing composites increase safety, decrease waste

Natural Process Design, Inc. has developed "polymer composites with unique toughness and strength by self-repair, which occurs at material interfaces and at damaged areas. This is not by hand repair, but by release of repair chemicals from within the composite itself. The hollow fibers are embedded in the matrix, and the chemicals they carry are released wherever and whenever cracking or other matrix damage occurs. The repair chemical flows into the crack, and crack faces are rebounded."Text is from Summary of Self-Repair Technology in Polymer Composites

Key Differentiators

"Airplanes that are safe to fly or can return home safely even if damaged, bridges that can withstand an earthquake and remain standing, boats that can resist damage to keep afloat, or oil rigs and pipelines that can resist damaging storms – these are the contributions of self repairing composites to the nation’s economic and social welfare beyond mere commercial profits. The savings range from lives spared to tax payer savings. On the competitive stage, U.S. industries have been poised to develop many more uses for composites but one technical flaw has hampered their performance, that is, safety and indeed predicable safe performance of composites. Internal damage is not dramatic, but very common in composites. Repair of internal damage is important in order that failures do not progress to ultimate catastrophic failure. Furthermore, microscale cracks are hard to detect unless they have developed to macroscopic scale flaws. Nondestructive evaluation techniques have limited ability to detect microcracks. Damage can be repaired in the field by hand, but not all of the original strength restored."

Biomimicry Story

Nature often builds with materials that can self-repair--skin, insect exoskeletons, abalone shells, bones, starfish arms. Repair doesn't occur from outside the organism, but from within. Carolyn Dry from Natural Process Design, Inc. has applied this idea to create self-repairing polymer composites.

Challenges Solved

"[T]he use of polymers has grown so much [between 1995 and 2005] that polymer bridges exist and use of polymers in airplanes had doubled. This, despite the drawbacks of polymers in reliability and consistency, is because polymer composites have so many advantages over steel or concrete. These include: resistance to intrusion of environmental chemicals and water that could cause damage, increased/beneficial vibration damping, energy absorption, electromagnetic transparency, toughness, control of stiffness, high strength to weight ratios, and being lightweight to decrease dead load as well as transport costs. Polymer composites are three times stronger than steel and five times lighter. Composite materials have applications in rehabilitation of existing bridges as complete structural replacement or new construction""On the competitive stage, U. S. aircraft industries have been poised to develop many more uses for composites but one technical flaw has hampered their performance, that is, safety and indeed predictable safe performance of composites. Damage, which is internal, is very common in composites. Repair of this damage is important in order that failures do not progress to catastrophic failure. However, delaminations are hard to detect. Damage is usually repaired in the field by hand, but not all of the original strength is restored."