Composite patch repair of steel plates with fatigue cracks growing in the thickness direction

The behaviour of steel members with fatigue cracks growing in the thickness direction and strengthened with an adhesively bonded composite patch is assessed in this paper both analytically and experimentally. Analytical models for two different fracture fatigue parameters, namely the stress magnification factor for the crack in the steel member and the energy release rate for debonding at the steel/adhesive interface, are developed based on finite element analyses. These models can be readily employed in fatigue calculations. In order to verify the analytical models, an experimental investigation is also carried out. To this end, fatigue tests of specially designed and prepared patched cracked steel specimens are carried out and crack growth data are found to correlate reasonably well with their analytically obtained counterparts.