Using a Meshless Method to Predict the Strength of Adhesive Single Lap Joints

Abstract

The application of lighter materials in the automotive, naval and aeronautic industry allows to reduce significantly the emissions. Composite materials are a good solution, since they are lighter than conventional construction metals. However, composite structures do not tolerate bolting or riveting, which introduce holes into the composite substrates leading to delamination, tearing or burrs. Thus, adhesives are the most commonly used bonding solution. This work aims to show the efficiency of a meshless discretization technique in the analysis and structural simulation of adhesively bonded Single Lap Joints (SLJ) made of composite substrates. Meshless methods are advanced discretization techniques capable to discretize the problem domain using an unstructured nodal cloud, which allow a much higher discretization flexibility when compared with mesh-dependent techniques, such as the finite element method. Although the literature describes several meshless techniques, this work will use the radial point interpolation method (RPIM), a very popular and robust interpolation meshless methods already applied to a wide variety of structural problems. In order to deal with the material interface regions, this work proposed a new numerical technique for the RPIM that allow to efficiently recognize and simulate the interface. This work also aims to assess the use of the Critical Longitudinal Strain (CLS) criterion when performing the strength prediction of SLJ made with composite substrates simulated with the RPIM, and to determine if there is a general rule that can be followed when determining the critical parameters. Three adhesives were analysed, Araldite AV138, Araldite 2015 and Sikaforce 7888, varying the adhesive length. The results have shown that the stress components along the adhesive mid-thickness line obtained with the RPIM were similar with the FEM and that the CLS criterion provided accurate strength prediction.