Fatigue Failure Evaluation of Boron/Epoxy Patches Using Thermal Wave Imaging

Mechanical fastening or riveting of metallic doublers is traditionally used for repairing cracked structures, multi-site or wide-spread damage and any other common flaws detected during inspection of aging aircraft. This method of repair can severely reduce the initiation fatigue lifetime and the damage tolerance of the structure [1]. Several researchers for example [2–6] have demonstrated the effectiveness of bonded composite doublers as a method of repairing aircraft structures. Bonded boron/epoxy repair patches for aging aircraft appear to offer many advantages over traditional methods of repair. They are thin and light weight and can be aerodynamically tailored to reduce drag force. They are conformable to contoured surfaces, access is needed only from one side of the repair area, and they can be used in some areas where riveting is difficult. Structural reinforcement without the addition of rivets provides for a more uniform stress distribution and eliminates ancillary damage which can be caused by rivets. In addition they provide excellent corrosion resistance and are easier to inspect using NDE techniques [7]