Investigation of Impact Damage in Composites with Infrared Thermography

This work is concerned with low-velocity impact of composite materials which are mainly used for aerospace applications. Infrared thermography is used with a twofold function of surface temperature mapping when the specimen is being impacted and of non destructive evaluation (NDE) technique. Several specimens were fabricated involving a polymeric matrix reinforced with carbon, or glass fibres and a fibre metal laminate (hybrid composite such as Glare (R). Specimens were first non-destructively inspected with lock-in thermography to search for manufacturing defects, then impacted each at a different energy and again inspected with lock-in thermography. Impact tests were carried out with a modified Charpy pendulum including an impactor of hemispherical nose 24 mm in diameter. The impact energy was varied in the range 2-19 Joule by varying the height of the Charpy arm. The SC6000 infrared camera was used to view the specimen surface opposite to impact; thermal images were acquired at 96 Hz. The obtained results show that the impact on-line monitoring supplies useful information for the material characterization. In particular, the analysis of the hot zones provides understanding of the damage origin and propagation.