Composites for Reinforcement of Damaged Metallic Aircraft Wings

Abstract

Advanced composites, because of their inherent directional properties and ability to take complex contours are ideally suitable for repairs even in aged metallic aircraft structures. The composite materials can be suitably tailored to suit the strength and stiffness requirement at location of the damage on the parent structure. The laminate patch can be bonded to the structure. This avoids the use of large number of fasteners that are required for repair with metallic repair patch. A composite patch repair has been carried out on a military aircraft wing. The skin and the spar flange near the landing gear part were cut in order to gain access to a loosened bolt. With a request from HAL (Nasik), National Aerospace Laboratories (NAL) has taken the responsibility of designing and realizing composite repair at the damaged locations. The geometry and lay-up of the patches have been arrived at based on the strength requirements. The patches were fabricated at NAL and the repair was implemented on the aircraft. The quality of the patch bonding was checked using non-destructive testing (NDT). The aircraft has completed about 130 hrs flying with the repair. The repair was certified by the regulating authority and has been recommended to be implemented on other twenty aircraft also. This task has been completed successfully and all the aircraft are flying. This is an important achievement both for NAL and HAL (Nasik). This paper discusses the repair design, patch fabrication and implementation of the repair.