Hot Press Joining Optimization of Polyethylene to Aluminium Alloy AA6061-T6 Lap Joint Using Design of Experiments

Abstract

The hot press method is used to join a poly-ethylene plate of thickness 4 mm with an aluminium alloy AA6061-T6 plate of thickness 1.5 mm. A preanodizing process is crucial for the success of such joint. The anodizing was performed under a current density of 200 A/m², temperature 24°C, sulphuric acid 5 wt.% and for a 60 minutes. Three period parameters were considered in the hot pressing process; temperature: 115 and 135°C, pressure: 2, 6, and 10 bar and pressing time: 1, 2, 3, 4 and 5 minutes. The joint specimens are tested by shear tensile test, microstructure, energy dispersive spectrometry, differential scanning calorimetric and thermo grvanometric analysis. The results of shear tensile were analyzed using design of experiments. Minimum and maximum shear tensile force were found at temperature T = 115°C where; F_min = 680N and F_max = 2800 N. From Pareto chart, the applied pressure had the most significant effect on the shear tensile force of the joint specimens compared to temperature and joining time. The main effect plot showed that optimum value of shear tensile force was obtained at joining conditions of T = 135°C, P = 6 bar and t = 3 minutes. The tested specimens exhibited an interfacial shear failure, extension and necking in the region of polymer with a ductile fracture. The mechanical interlocking of polymer element in the anodizing surface is approximately 15 µm. The melting point and glass transmission temperature of PE are decreased after the hot press.