Comparison between Different Patch Shapes of Bonded Composite Repairs on Metal Matrix Composite: A Numerical Analysis

In recent years, composite patching technique is widely used in aerospace industry. This technique prevents the crack in any material from propagating further. This prevents the complete damage of the component in near future and hence increases the life of the component. Metal Matrix Composites or MMCs are a new set of materials that have become popular in aviation and space industry. MMCs are basically made up of minimum two parts, one is the metal and other may be a metal or another material such as ceramic or an organic compound. Due to properties such as resistance to high-temperature, high thermal conductivity, low CTE, and high specific stiffness and strength, these are widely used in space system applications. The effectiveness of bonded composite repairs depends on patch material, patch shape and dimensions, its thickness, adhesive used, properties of base material and many other parameters. In this paper, the parameter under consideration is the shape of patch for double side or Symmetrical patching. The most commonly used matrix material is Aluminum. Hence, the base material used for analysis is Aluminum matrix composite. Adhesive used for current endeavor is Cytec's FM-73 (an epoxy nitrile system with a recommended cure temperature of 250 F). The central crack model of MMC 2D plate is concerned to locate the path of crack propagation. Further the crack is repaired using Boron Epoxy patch. Stress intensity factor at is calculated for various patch configurations. The patch shapes under study are rectangular, elliptical, butterfly and arrowhead. Comparative study of different patch shapes show that arrowhead configuration gives the desired output while other shapes can also be used in specific cases. Also, the technique of bonded composite patches proves to be an effective repair method for metal matrix composites.