Abstract:

In this article the strength analysis of cracked plates repaired with composite patches is investigated. Emphasis is laid on the consideration of various viscoelastic behaviors of patches or adhesives. By taking the forces in the repaired zone as basic unknowns, the problem is formulated exactly and the stress intensity factors at crack tips are obtained in closed form for point bond cases. For full and partial bond cases, the problem is reduced to a Fredholm integral equat on of the first or second kind, depending on whether the effect of the adhesives is excluded or included in the consideration. Through numerical solution of the Fredholm integral equations, the variation of the stress intensity factors with respect to time is obtained and presented in graphical and tabular forms for various patch sizes, viscoelastic models, locations of the patches and bonded ranges. The results indicate that the stress intensity factors increase progressively with time, or, the reinforcement effect of patches on cracked plates decays monotonously due to the viscoelastic behavior of patches or adhesives. This paper shows that the viscoelastic effect should be taken into account in the strength analysis of cracked structures repaired by composite patches and provides the idealized models, basic equations and solution methods for the problem.

Key words: crack, composite patch, viscoelastisity