Fiber Bragg Grating Sensors, FBGSs, are very promising for Structural Health Monitoring, SHM, of aerospace vehicles
due to their capacity to measure strain and temperature, their lightweight harnesses, their multiplexing capacities and
their immunity to electromagnetic interferences, within others.
They can be embedded in composite materials that are increasingly forming an important part of aerospace structures.
The use of embedded FBGSs for SHM purposes is advantageous, but their response under all operative environmental
conditions of an aerospace structure must be well understood for the necessary flight certification of these sensors.
This paper describes the first steps ahead for a possible in future flight certification of FBGSs embedded in carbon fiber
reinforced plastics, CFRP. The investigation work was focused on the validation of the dependence of the FBGS's strain
sensitivity in tensile and compression load, in dry and humid condition and in a temperature range from -150°C to 120°C.
The test conditions try to simulate the in service temperature and humidity range and static load condition of military
aircraft. FBGSs with acrylic and with polyimide coating have been tested. The FBGSs are embedded in both,
unidirectional and quasi isotropic carbon/epoxy composite material namely M21/T800 and also MTM-45-1/IM7.
Conventional extensometers and strain gages have been used as reference strain sensors.
The performed tests show an influence of the testing temperatures, the dry or wet specimen condition, the load direction
and the coating material on the sensor strain sensitivity that should be taken into account when using these sensors.