Comparison between non-destructive evaluation techniques and integrated fiber optic health monitoring systems for composite sandwich structures

Non-Destructive Evaluation (NDE) methods have been adapted to composite san dwich structures in order to detect damage, in particular impact induced da mage. Using three coupons representative of radome structures, several tech niques were tested: ultrasonics, the Electromagnetic/InfraRed method (EMIR) , stimulated shearography and stimulated infrared thermography. The extensi on of the measured damaged area was taken as a criterion, showing that stim ulated shearography and ultrasound are the most sensitive methods. Moreover , two integrated Health Monitoring Systems (HMS) were tested, based on the one hand on microbending sensitive fibres and Optical Time Domain Reflectom etry (OTDR), and on the other hand on Fibre Bragg Grating (FBG) sensors. Th e experiments demonstrated that HMS can detect damage with sensitivity comp arable to that of the external NDE techniques.