The influence of mechanical fastener assembly geometry on the load-bearing capacity of joints used in composite aircraft structures

Abstract

This paper presents the results of experimental studies and numerical simulations of the effect of the assembly geometry of mechanical fasteners on the load-bearing capacity of single-lap joints in composite components made of quasi-isotropic carbon-epoxy laminate (CFRP). Three types of joints were examined: mechanical, adhesive, and hybrid. The effects of the overlap length and the distance of the assembly hole from the edge of the overlap on the static load-bearing capacity of the joints and their fatigue life were analyzed. The studies were supplemented by a numerical analysis using the finite element method (FEM) in the Ansys Workbench environment, covering the stress distribution in the laminate, the adhesive joint, and the fasteners. It was shown that hybrid joints achieve the highest static load-bearing capacity and fatigue life — up to seventy times greater than that of mechanical joints. Experimental tests were conducted for various distances of the assembly hole from the overlap edge: ranging from three to four times the hole diameter for mechanical joints and twice the hole diameter for hybrid joints. The results obtained may serve as a basis for formulating design guidelines for composite aircraft structure joints.