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ABSTRACT:Adhesively-bonded patches are used for repair of different types of damages such as holes, notches, scratches, cracks etc. occurring in metallic as well as composite structures. The composite patching is the most widely used method of restoring the load-carrying capacity of the weakened structure. Due to the rapid growth of aerospace industry, analysis of adhesively-bonded patches to repair cracked structures have been the focus for many years. Most of these studies investigated repaired structures using linear analysis and demonstrated the viability of adhesively-bonded patch-repairs as a means to improve the durability and damage tolerance of cracked metallic structures efficiently and economically.Many researchers performed more intensive research on the method and presented the advantages of a composite material patch used for the cracked plate repairing. It was found that the bonded patch method not only reduces the weight but also increases the service life.In this research work, the analysis of cracked metallic and composite plates which are repaired by bonded-composite patches is performed using Finite Element Analysis package FRANC2D/L. This package is available with its corresponding mesh generating program CACSA. They are developed by Cornel Fracture Group, Cornel University.In this study, various fracture parameters for the structures are found out. It revealed that, the application of the bonded composite patches effectively reduces the stress intensity factor (SIF) near the crack tip and hence retards or eliminates the crack propagation. As the chances of fracture are almost reduced, the life of the structures increases by almost double of the initial. The main advantage of this patch repair technology is that, it doesn't increase the weight of the structure too much.

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