Mitigating stress concentration through defense hole system for improvement in bearing strength of composite bolted joint, Part 1: Numerical analysis

Abstract

The use of defense hole system allows the flow of the stresses to be redistributed by introducing auxiliary holes in the low stress area near the main hole. However, the question remains on the optimal configuration of the defense hole system for effective stress mitigation at the bolt-hole region and, hence, increasing the bearing capacity of particular composite bolted joints. This study presents the influence of defense hole system geometrical design on the stress reduction in a single-bolt, double-lap composite bolted joint. The nonlinear material behavior of the joint was simulated using ANSYS through a progressive failure model, considering the circumferential and radial stresses at bearing, shear-out, and net tension regions of the bolt-hole. It was found that the stress has been reduced between 2.3% and 6.1% for the narrow laminates over a range of E/ D ratios (1–5) with the benefits of the defense hole was clearly marked at DS = 2 D and DHD = 0.75 D. In contrast, for those of wider laminates, the stress reduction ranged from 1.9% to remarkably 18.6%.

Experimental and numerical investigation of the transition zone of locally steel-reinforced joining areas under combined tension–bending loading

“…by changing the hole geometry 9 or by using additional holes as softening measures. 10 The latter approaches have the aim to homogenise the stresses occurring in the joining area and to reduce the maxima. There are also approaches to combine the properties of composites and metal, e.g.…”

The effects of composite laminate stiffness and loading on stress resultant concentration factor around a hole

“…Khechai et al 23 evaluated the stress distribution around circular holes in thin isotropic and symmetric laminated plates subjected to uniaxial loading by using a specially formulated quadrilateral finite element. Othman et al 24 used FEA and the concept of defence hole system (DHS) to reduce stress concentration in holes of composite bolted joints. Darwish et al 25,26 used three-dimensional FEA to formulate stress concentration around circular countersunk holes in composite orthotropic plates under uniaxial loading.…”

“…Othman et al. 24 used FEA and the concept of defence hole system (DHS) to reduce stress concentration in holes of composite bolted joints. Darwish et al.…”