Innovative load application into oscillation-loaded fibre-reinforced plastic structures

Abstract

In different industries, the amount of used fibre-reinforced plastics (FRP) is increasing. For these materials, thermal joining technologies such as welding cannot be used. Therefore, a demand for innovative joining methods arises. Under load a complex stress distribution and stress peaks become apparent in FRP joints. Two different approaches to handle such peaks are investigated. The first approach uses adhesive bonding with an epoxy adhesive. To reduce the emerging stress peaks, an elastomer layer is locally introduced into the laminate that is to be joined. The second approach is the application of multi-loop carbon roving rosettes to reinforce bolt-loaded open-hole laminates. These multi-loop rovings consist of turns around the hole and free slings in the design area around the hole; they are applied onto the laminate. To experimentally determine the impact of the elastomer as well as the rosette application, quasi-static as well as fatigue tests have been conducted. On this basis, characteristics of the new approaches are compared to reference joints. For local elastomer integration, experiments show that for joints of carbon FRP with aluminium the bearable load cycle number is raised. The rosettes significantly increase local bearing capacity. To underline the potentials for industrial application, investigations concerning automation to manufacture these joints are presented.