The effect of the setting force on the static strength of a blind rivet nut set in CFRP

The continuous increase of structural composite applications urges the need for a profound understanding of the behaviour of mechanically fastened joints in lightweight composite materials. As opposed to adhesive bonding, mechanical fasteners come with easy installation and disassembly processes. However, mechanical fasteners are inherent stress raisers and therefore often deemed inappropriate for usage in composite structures. In this paper, the static mechanical strength of a blind rivet nut (BRN) set in carbon fibre reinforced plastic (CFRP) is experimentally investigated. The mechanical strength is assessed by conducting a bearing test, a push-through test and a filled-hole tension test. The influence of the setting force on the static strength of the BRN is investigated for two composite plates consisting of unidirectional (UD) carbon fibre layers and woven carbon fibre layers, respectively. The failure modes are analysed and supported by finite element simulations enabling to predict the stress state during and after setting. It is shown that the setting force enables to control the stress state within the laminate. Moreover, the compressive stress state after installing the BRN generally increases the static mechanical strength. The results increase the potential usage of the BRN as a fastener for CFRP.