Material Senses, Terminates Damage

A novel autonomous material that uses "shape-memory" polymers with an embedded fiber optic network may be able to not only sense damage in structural materials, its creators say, but even make repairs.

The technology brings to mind the human-like, robot assassin known as "The Terminator," which can regenerate its structure after being severely and extensively damaged. But this scenario is rapidly becoming less far-fetched as recent advances in structural health monitoring systems lead to a variety of ways to identify damage to a structural system.

You've seen it in movies: the human-like, robot assassin quickly regenerates its structure after being damaged beyond recognition. This "Terminator" scenario is becoming less far-fetched as recent advances in structural health monitoring systems have led to a variety of ways to identify damage to a structural system. (istockphoto)

The aim of the material developed by Henry Sodano and colleagues at Arizona State University is to create autonomous adaptive structures that mimic the ability of biological systems such as bone to sense the presence of damage, halt its progression and regenerate itself.

The shape-memory polymers' embedded fiber-optic network functions as both the damage detection sensor and thermal stimulus delivery system to produce a response that mimics the advanced sensory and healing traits shown in biological systems. An infrared laser transmits light through the fiber-optic system to locally heat the material, stimulating the toughening and healing mechanisms.

Thermal image of the temperate gradient created by a metal test specimen undergoing the photothermal heating method. (Image: American Institute of Physics)

The new material can sense damage, such as cracking in a fiber-reinforced composite. The system is capable of increasing the toughness of a specimen by 11 times. After toughening the specimen, the crack can be closed using the shape-memory effect to recover an unprecedented 96 percent of the object's original strength. In fact, after the crack is closed, the new material is nearly five times as tough as the original specimen, even though it has been strained past its original failure strain point by a factor of four. The material and healing process can be applied while the structure is in operation, which has not been possible with existing healing techniques.

The article, "Autonomous Materials with Controlled Toughening and Healing" by Michael Garcia, Yirong Lin, and Henry Angelo Sodano appears in the Journal of Applied Physics.