Pulsed thermography for non-destructive evaluation and damage growth monitoring of bonded repairs

Development of Infrared Techniques for Practical Defect Identification in Bonded Joints

“…Finally, using composites it is generally possible to manufacture a sample that has an inherent weakness in its layup which is prone to failure in a particular mode and a particular location when subjected to loading. Such contrived samples have been used to produce delaminations in composites or disbonds in adhesive bonds [37]. The nature of creating a 'real' defect is that the precise location and geometry of the defect is not known prior to experiments therefore they can be used to conclusively 13 parameterise defect comparisons of a developing technique.…”

“…Bonded joints between CFRP reinforcement patches and concrete have been assessed using PT to identify a range of defect types including unbonding, where no adhesive is present, delaminations, where CFRP patches delaminate from each other, and finally debonding, where a defect occurs between the CFRP and concrete [106]. Variations in the pulse duration and heat lamp to sample distance were studied and minimum strength and pulse durations were 37 suggested to study such composite repairs. Omar et al [13] used thermography in transmission mode to study bond integrity of a plastic welded joint between two cups.…”

“…A study to assess bonded repairs using graphite epoxy composite patches on aircraft has also been carried out using PT and PPT [37]. The bond line was inspected for signs of delamination and disbonds.…”

Bonded repair issues for composites: An investigation approach based on infrared thermography

“…It is to note that some post-processing of derived thermal fields may be necessary to reveal and localize more precisely these heterogeneities [10,14,15]. Regarding applications in the repair context, active IRT usually focusses on the detection of artificial defects introduced within the glue joint: Teflon inserts to simulate delaminations and disbondings [16][17][18], grease mould release to represent kiss-bonding or dry fibers to account for porosities [19]. IRT is Jess common in the repair field.…”

Thermography inspection for early detection of composite damage in structures during fatigue loading

“…The active flash thermography technique utilizes a flash tube enclosed within the cylinder and allows for the measurement of through-the-thickness diffusivity [4]. A small torsion load is applied (both clockwise and counterclockwise) during the flash thermography inspection and a difference thermography processing technique is applied to remove thermal variations associated with normal material variations [5][6][7]. It has been found that the combining the application of a static torsion load during the flash inspection with difference processing improves defect contrast and helps to size the defects [6].…”