Design Testing for Expanded Bushings in Composite Materials for Use in Helicopter Applications

Rotary wing manufacturers have been taking advantage of composite strengths, such as formability and weight savings, in new aircraft design for many years. Composite materials can be challenging at critical joints involving composite and metallic material joints. Expanded Fatigue Technology Inc. (FTI) products, such as high interference fit bushings, have a proven history in metallic structural and dynamic components on helicopters for over a quarter-century. FTI has modified their expanded bushing method for composite structures. For these applications, the process changes include lowering the expansion so as to not reduce the structural integrity of the composite laminate. Extensive testing has been performed to understand the versatility of the expanded products. Some of the expected advantages of using these expanded products in composite laminate structure are: process reliability, increased retention, hole protection, joining easement, and lightning strike/conductivity improvement.