Fraunhofer: Sensor in bio-tissue monitors the condition of roads

Researchers at the Wilhelm Klauditz Institute (WKI) of the Fraunhofer Institute for Wood Research have developed a sensor system based on flax fibers that can provide information about the condition of the road surface when placed in asphalt roads. Damage, such as cracks and holes, can be detected in real time.

According to a press release from the Fraunhofer Institute, it is only possible to determine the actual condition of the inside of an asphalt road using complex measurement methods. To detect damage in deeper layers, drill samples have to be taken and the asphalt partially destroyed in the process. This is not economical.

Woven sensors

The WKI scientists' method therefore relies on sensor mats embedded in the asphalt to detect damage at an early stage. The carrier material is a fabric made of flax fibers in which 1 mm thick conductive sensor wires are woven. The scientists create the sensor technology using a double-rapier weaving machine that can produce sensor mats with a width of 50 cm and any length.

The strength is achieved through a high yarn thickness, which also leads to a high resistance to displacement. This is because the fabric must be so stable that it does not cause any undesirable structural disturbances in the asphalt. Larger yarn spacing also helps here, the researchers explain. The strength is high, they say, and the sensor material can withstand stress during installation and later from the weather and general road wear. The sensor mat is therefore suitable for continuous measurement of data that provides information on the condition of the road.

A measuring device is used to measure changes in resistance in the sensor wires resulting from damage to the asphalt layer. The data is then analyzed by analysis software. The software is based on artificial intelligence (AI). It determines damage that has already occurred but can also make predictions for expected damage. The aim is for road authorities to recognize problems at an early stage and for road builders to repair them—before they become expensive.

The data is to be prepared and visualized in a comprehensible way via an Internet platform to make it available to authorities, residents, companies, road users, and other people affected by any construction measures.

Laboratory and practical tests

Initial tests in the laboratory have been successful. Practical tests are currently being carried out on a road in an industrial estate that is fully equipped with the sensor material. Measuring points are already recording data on the changes in resistance. These are so precise that the exact axle loads can even be read off when a loaded vehicle passes. Further tests still have to show whether precise conclusions can also be drawn about road damage.

The WKI research project is funded by the Federal Ministry of Transport. Uhlig & Wehlig GmbH, AS+BE Asphalt- und Betonstraßenbau GmbH, Time4Innovation UG, and the two universities of Magdeburg-Stendal and Hanover are also involved in the project.

(olb)