Degradation monitoring of impact damaged carbon fibre reinforced polymers under fatigue loading with pulse phase thermography

Carbon fibre reinforced polymers were subjected to impact damage and fatigue load in tension-compression. During fatigue the development of the defects was monitored with pulse phase thermography using optical excitation. The development of phase angle difference measured between damaged areas and undamaged areas of the specimen shows a similar behaviour as degradation curves based on the variation of the material's modulus. Additional investigations with ultrasonic c-scans, radiography and microscopy show correlations between the phase angle difference change and the accumulation, initiation and growth of delaminations, cracks and the geometrical dimensions of these defects.