High-performance fibers that have been exposed to high temperatures usually lose their mechanical properties undetected and, in the worst case, can tear precisely when lives depend on them. For example, safety ropes used by fire brigades or suspension ropes for heavy loads on construction sites. Empa researchers have now developed a coating that changes color when exposed to high temperatures through friction or fire.
source https://phys.org/news/2021-01-fiber-color-changing-coating-mechanical-stress.html
