Researchers from the National Institute of Standards and Technology (NIST) have developed a way to embed a nanoscale damage-sensing probe into a lightweight composite made of epoxy and silk.

The "mechanophore" sensor could be used to speed up the testing of products, such as high-performance sporting goods, weather-resistant bridges, and advanced cars.

The NIST team created their probe from a dye known as rhodamine spirolactam (RS), which changes from a dark state to a light state in reaction to an applied force.

In the experiment, the molecule was attached to silk fibers contained inside an epoxy-based composite. As more and more force was applied to the composite, the stress and strain activated the RS, causing it to fluoresce when excited with a laser.

Although the change was not visible to the naked eye, a red laser and a microscope built and designed by NIST were used to take photos inside the composite, showing even the most minute breaks and fissures to its interior, and revealing points where the fiber had fractured.

The team will continue to research ways that the mechanophore could be used to improve standards for existing composites.

“We now have a damage sensor to help optimize the composite for different applications,” said Jeffrey Gilman, who led the team doing the work at NIST. “If you attempt a design change, you can figure out if the change you made improved the interface of a composite, or weakened it.”


Also: Learn how a NASA Sensor Supports Flexible Aircraft Design.