Infrared Thermography assisted evaluation of static and fatigue Mode II fracture toughness in FRP composites

The work proposes the combined use of a Modified Transverse Crack Tension (MTCT) test coupon and Infrared Thermography, to evaluate the static and fatigue behaviour of Fibre Reinforced Polymer composites under Mode II delamination. Artificial delaminations starters are added to the TCT coupon, whose effects on the Strain Energy Release Rate are discussed. Infrared Thermography and Thermoelastic Stress Analysis are implemented to investigate stresses and delaminations growths on two FRP materials: a pre-preg IM7/8552 carbon fibre-epoxy and a glass-fibre reinforced epoxy laminates. The thermographic, thermoelastic and second harmonic signals have been obtained and used to monitor the onset of instable crack growth under monotonic loading, and the delamination growth under fatigue loading. The use of such full-field non-contact thermographic parameters allows a further and effective insight on the behaviour of TCT specimens, providing useful information for the characterisation of the Mode II delamination behaviour under both static and fatigue conditions.