Andrey Stepashkin's team developed soft magnetic circuits measuring 10-60 microns in diameter. Credit: NUST MISIS

Researchers from the National University of Science and Technology (NUST) Center of Composite Materials have developed soft magnetic circuits that provide a non-contact method of measuring the internal stresses of composite materials used in aerospace and aircraft engineering.

The team’s findings, published in the Journal of Alloys and Compounds, describes amorphous soft magnetic circuits measuring 10-60 microns in diameter, which are wired into the layers of carbon fibre in materials during the manufacturing stage to form a grid of stress-sensitive points.

“It is now possible to more effectively assess the degree of internal damages during the operation of aircraft parts, oil pipelines, ship hulls, and other industrial and transport facilities,” said NUST scientist Alevtina Chernikova.

Materials under stress respond differently to external magnetic fields, enabling the soft circuits to detect stresses across the entirety of the material. The circuits are connected to a sensor, known as the sticker, which is embedded into the material during the manufacturing stage and can send information to scientists. The system only uses a single sticker, making the process a much simpler and faster one than previous systems.

Internal stresses in composite materials, which can arise and accumulate following manufacturing due to operating loads and the external environment, have historically been difficult to measure. Traditional non-contact methods, such as the use of ultrasonic waves, enables researchers to detect defects which have already occurred, but does not provide information on the distribution of stresses through the structure.

“We have made the first step of a long journey,” said Center of Composite Materials senior research associate Andrey Stepashkin. “But we already see a practical application of our development.

“In addition, it has more features: the micro-wire mesh introduced into the material can provide an additional drain of the static charge that occurs in fiberglass structures,” he added. “Our wires are quite capable of replacing metal grids which are now inserted into these materials.”