Improved Structural Joint Concepts

Abstract

The joining of composite materials used in airframe structures has always presented a challenge to the structural engineer. As part of a Survivable Affordable Repairable Airframe Program (SARAP) agreement, research on three advanced joining concepts was conducted to identify and validate designs that would provide improved structural efficiency when compared to conventional joining methods. The first involves using finger joints in thin laminates to produce a joint with high specific strength compared to typical joining methods. The second utilizes a derivative of needling for stabilized dry fabric pre-forms to improve through-the-thickness laminate and joint properties. The third concept focuses on compression preload to improve the performance of a typical lap joint. Within each concept, coupon or element tests were used to validate the performance of these alternative configurations. This paper presents both analytical predictions and test results documenting the effects of these improved joining methods.