Fatigue Damage Prediction for Bonded Composite Repairs Applied to Metallic Aircraft Structures

This paper describes the initial development of methods for predicting the fatigue life of bonded composite repairs applied to cracked aluminum aircraft structures. Bonded repairs offer great potential in stopping or slowing crack growth. The benefits of bonded repairs when compared to riveted repairs are significant, and include improvements in fatigue life, inspectability, and cost. The main barrier to the widespread use of this technology is the lack of methods for ensuring damage tolerance and durability [1–3].

In this paper, approximate analytical equations are developed to characterize both disbonding and crack growth in a repair applied to a center-cracked plate. The equations are in a form suitable for use in probabilistic risk assessments and inclusion in industry codes and standards, and have been validated against a boundary element model. Comparisons of fatigue life predictions with results from published experiments illustrate the importance of cracked plate geometry and bending on the rate of cracking and disbonding.