Three-Dimensional Strain Analysis of Single-Lap Bolted Joints in Thick Composites Using Fibre-Optic Gauges and the Finite-Element Method

Abstract

Bolted joints involving composite plates used to be almost entirely dedicated to aerospace applications. As the need for energy conservation has increased, the field of composite bolted joints has found new applications in ground armoured vehicles. Thick panels able to withstand large in-plane and impact loads are critical. The present investigation evaluates the interior strain field, through the thickness, of a composite plate connected to an aluminium panel with a single-lap bolted joint. The area of interest is the bearing plane region close to the hole because of the presence of stress concentrations that heavily modify the stress field. Experimental data for the bolted joint were recorded by fibre-optic strain gauges that were embedded in the bearing plane of the composite plate. Numerical analyses were performed using ANSYS as a pre-processor and LS-DYNA as a solver. The overall goal was to evaluate the magnitude of contact strains around the hole and through the thickness of the composite. These values were analysed and compared with the finite-element method results: the finite-element analysis correlated reasonably well with the experiments. An investigation of error causes was also carried out, in particular to evaluate the influence of incorrect gauge positioning and the effect of friction coefficients. General design considerations were finally provided, based on the complete three-dimensional finite-element analysis.

Modelling bolted joints using a simplified bolt model

“…The fundamental task of the machine modelling phase is to find a compromise between the level of its model simplification and the expected accuracy of its modelling. This is particularly meaningful for modelling systems with many different elements being in a contact [Zimmerman and Śnieżek 2009, Restivo, Marannano and Isaicu 2010, Molnár et al 2014, Szulc, Malujda and Talaśka 2015.…”

Experimental and numerical analysis of aluminum-aluminum bolted joints subject to an indentation process

“…Restivo et al [9] perform a numerical-experimental study of a single-lap bolted joint involving a thick composite laminate and an aluminum plate. Experimental data, recorded by fiber-optic strain gauges that are embedded in the bearing plane of the composite plate, are compared with those obtained thought FE numerical analysis.…”

“…Also, tests are subjected to both static and fatigue conditions. Several FE numerical models reproducing a bolted single-lap joint are developed using the ANSYS code [9]. Numerical analyses are focused on the evaluation of stress distribution on the adherent 3 mm thick, in the area surrounding the hole and at the end of the loading phase, on both type of analyzed joints.…”

Experimental study of loosening behavior of plain shank bolted joint under dynamic loading

“…The loosening and sliding behavior of nut bolt fastener under transverse loading conditions was investigated by Hattori et al (2010) They showed that loosening behavior of nut bolt joint shows the same occurrence if the transverse load applied in the opposite direction and when transverse cyclic load applied to the joint, bolt axial tension slowly decreases and at the worst stage not only loosening occurs but bolt fails in fatigue also. Restivo et al (2010) collected experimental data for the bolted joint by fibre-optic strain gauges that were embedded in the bearing plane of the composite plate. Denavit et al (2011) conducted research for better understanding of the effect of fillers in bolted steel connections.…”