Strengthening of old metallic structures in fatigue with CFRP materials

Research regarding strengthening of old metallic structures using unidirectional carbon fibre reinforced polymer(CFRP) laminates has shown very usable to lengthen the service life of structural members in tension With the basis in a 110 year old riveted beam, centre notched test specimens have been manufactured and tested in fatigue with constant amplitude.

The test series focuses on different CFRP configurations with and without prestressing and it has been shown possible to slow down crack growth in the steel substrate. The test specimens with prestressed CFRP laminates showed the ability to stop crack growth completely. A simple fracture mechanic study using linear elastic fracture mechanics has been used to show the effect of both non- and prestressed repairs, in relation to the stress intensity factor.

Furthermore stresses in the bond between the steel and CFRP has been analyzed according to a direct linear elastic theory and compared with measured results. The experiments showed a good match between theory and measurements.