Impact damage in GFRP: New insights with infrared thermography

The aim of the present paper was to investigate the behaviour of glass fibres reinforced polymer (GFRP) under low velocity impact with infrared thermography. Several specimens were considered which include unidirectional E-glass fibres embedded in epoxy resin matrix with symmetrical stacking sequence [02/902]S. These specimens were impacted with modified Charpy pendulum by varying shape (ogival and hemispherical) and diameter (18 and 24 mm) of the hammer and the impact energy in the range 4–25 J. The side opposite to impact was monitored by infrared cameras. Sequences of images were acquired with starting and ending times set so as to include the evolution of thermal phenomena from thermo-elastic to thermoplastic phases. Infrared thermography was also used for non-destructive evaluation of specimens before and after impact. The obtained results show that on-line monitoring of the impact is useful for material characterization. In particular, it is shown that the onset of heat generation loci corresponds to the onset of impact damage. From the analysis of temperature maps it is possible to get information about damage threshold and extension. One main finding regards the relationship between the damaged area and the effective striking surface.