Load-induced debonding of FRP composites applied to reinforced concrete
2009
Fiber-reinforced polymer (FRP) composites are widely used to increase the flexural and shear capacity of reinforced
concrete (RC) elements. One potential disadvantage is that strengthened surfaces are no longer visible and cracks or
delaminations that result from excessive loading or fatigue may go undetected. This research investigated thermal
imaging techniques for monitoring and evaluating load-induced delamination of FRP composites applied to small scale
RC beams. Two beams (3.5 in x 4.5 in x 58 in) were loaded monotonically to failure. Infrared thermography (IRT)
inspections were performed at various load levels through failure using a composite phase imaging technique. Two
similar beams were tested in fatigue and periodic IRT inspections were performed at 50,000-cycle intervals. Individual
phase values for each pixel were designated as "well-bonded", "suspect" or "unbonded" to indicate the quality of FRP
bond. Suspect areas included regions of excess thickened-epoxy tack-coat and smaller installation defects in the
unloaded specimens. The long-term objective of this research is to develop a practical framework for conducting
quantitative IRT inspections of FRP composites applied to RC and incorporating these results into acceptance criteria
for new installations and predictions for the remaining service life of in-service FRP systems. This method may also
offer insight into the necessity for repairs to in-service systems.
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