Impact localisation with FBG for a self-healing carbon fibre composite structure

We demonstrated the localisation of impacts in orthotropic carbon fibre reinforced polymer (CFRP) composite materials to within a few centimetres, using a sparse array of fibre Bragg grating (FBG) sensors. This type of sensor is easily embedded in composites permitting the development of structures with integrated sensing capability. Impact location was determined by measuring the differences in time-of-flight of ultrasonic Lamb waves at three surface-mounted sensors. An algorithm was developed taking into account the angle dependence of the optical fibre sensor sensitivity and the variation of Lamb waves propagation velocity with direction and wave mode. The performance of FBG sensors for impact localisation was compared to that of standard piezoelectric transducers (PZTs), which are already widely used for that purpose. The FBG-based system showed promising potential for a non-intrusive impact detection system applied to self-healing composite structures.

► Self-healing composites require a system to localise damage events.
► An array of fibre Bragg gratings detects Lamb waves in a composite structure.
► Lamb wave velocity is measured as a function of angle with respect to the fabric.
► An algorithm is implemented to localise impacts using 3 FBG in an orthotropic plate.
► The method is less precise than PZT, but integration into the structure is less intrusive.