Fatigue behavior of novel hybrid fastening system with adhesive inserts

Abstract

A novel joining technique that incorporates the advantages of both bonded (lightweight) and bolted (easy disassembly) techniques was invented (Provisional Patent 61/658,163) by Dr. Gary Cloud at Michigan State University. The most basic configuration of this invention consists of a bolt that has a channel machined through the bolt-shaft that allows injection of an insert compound that fills the necessary clearance between the bolt and the work-pieces and acts a structural component. More sophisticated versions of the concept incorporate additional sleeves or inserts. In this paper the fatigue behaviour of composite hybrid bolted joints was studied. Composite plates were bolted with grade-five bolts and preloaded to a torque of 35 N-m. Two types of bolted joint configurations were evaluated. In the first case, a conventional bolted joint was studied. In the second case, pristine SC-15 epoxy resin was used as the structural insert in the hybrid fastening system. The joints were subjected to different fatigue loadings with the maximum loading level up to 80% of the joint ultimate failure load and stress ratio of R = 0.1. Results reveal considerable improvement of fatigue life of the novel fastening system compared with a conventional bolted joint.