Chapter 5 - Approximate Theory of Unsupported One-Sided Crack Patching

Abstract

This chapter presents an approximate method for analyzing the tensile stretching and bending of a cracked skin plate, which is repaired on one side, subjected to tension and thermal excursion. The method employs a hybrid approach, in which, the stage I analysis is performed within either geometrically linear or nonlinear theory, while stage II analysis is always within geometrically linear analysis. In addition, stage I problem has been solved approximately using the equivalent inclusion method that was extended to include analysis of the bending plates. On the other hand, stage II problem has been solved using the crack-bridging model within both Kirchhoff–Poisson and Reissner plate theories. The repaired structure is modeled as a plate containing a through thickness crack, bridged by tension and bending springs, whose stiffness constants are determined from a 1D analysis of a single-strap joint. The results from the crack-bridging model show that the Kirchhoff–Poisson plate theory would considerably overestimate the bending stress intensity factor, while the formulation-based on the Reissner's plate theory provides a reasonably good estimate of both the membrane and the bending stress intensity factors, when compared with results from a 3D Finite element (FE) analysis. The results show that a one-sided repair is still much less efficient in reducing the stress intensity factor than an equivalent two-sided repair.