In situ formation of strain sensors by breaking optical fibers in structural materials

This article describes the formation of strain sensors embedded in a matrix material by breaking a notched optical fiber in the matrix. When a specimen with an embedded optical fiber with a notch is tensile tested, fracture of the fiber at the notch occurs, producing an optical interference type strain sensor. During the formation process optical transmission loss is recorded. The case of multiply notched optical fibers is also considered and it is shown that the optical loss of the embedded optical fiber during tensile test increases with the number of breaks. Using bending, instead of tension, to form the sensor, allows a reduction of break pitch and consequently improves the local nature of the sensor. The multiple fractured type optical fiber sensor has also been used on an active laminate to monitor its curvature change during actuation.