Computational analysis of stress distribution in adhesively bonded hybrid sisal-glass reinforced high-density polyethylene composite

In this study, a computational investigation was conducted to analyze the stress distribution, specifically peel and shear stresses, in adhesively bonded hybrid sisal-glass reinforced high-density polyethylene (HDPE) single-side strap joints for automobile side-body panel applications. The analytical Variational Method (VM) and the Finite Element Method (FEM) based on the Cohesive Zone Model (CZM) were both used in this analysis. The upper steel adherend was modeled as isotropic, and the bottom hybrid composite was modeled as orthotropic with an orientation of [0/+45/90/−45/0] and a stacking order of [G-S-G] and [S-G-G]. The maximum interfacial shear stress was observed to be at the loaded edge, with a peak value of 1.03 MPa at an adhesive thickness of 0.75 mm. The maximum peel stress was observed to be 8.5 MPa at the same configuration. The FEM showed that increasing the thickness of adhesive beyond 0.75 mm decreased stress concentration but decreased the overall efficiency of load transfer. The results were very close to what the analytical variational method (VM) predicted, with differences of less than 5% in every case. The study confirms that an adhesive thickness of 0.75 mm gives the optimal balance between strength and stress distribution, minimizing edge effects and improving joint durability. These findings demonstrate the reliability of the developed computational framework for optimizing lightweight, sustainable, and high-performance adhesive joints for automotive structural applications.