Effect of interfacial nanostructures on shear strength of Al-PPS joints fabricated via injection moulding method combined with anodising

Abstract

The high-strength direct joining of metal to polymer has attracted increasing attention in the weight reduction of equipment. In this work, porous anodic alumina (PAA) films with different interpore distances and pore diameters were fabricated on the commercial 6063T5 Al alloy via anodising, followed by etching. Then, the glass fibre/mineral filling polyphenylene sulphide (PPS) was directly joined with Al by using injection moulding method. The relationships between the interfacial structure and bonding strength of Al-PPS joints were systematically investigated and discussed. Results showed that the shear strength of the joints was significantly affected by the porosity, wettability, and hardness of the PAA films. With the increase in etching duration, the porosities of the PAA films increased, whilst their contact angles decreased (from 110° to 20°). However, excessive porosity (>45%) could lead to the weakening of PAA films. In general, the shear strength of joints increased first and then decreased with the etching duration. The maximal joint strength of the Al-PPS joints was ~21.2 MPa, which reached ~82% of the theoretical limit (~25.5 MPa). The images observed by scanning electron microscope and atomic force microscope indicated that the depth of PPS injected into the nanopore could reach >500 nm. The fracture surfaces of the Al-PPS joint with the highest strength could be divided into three different zones in accordance with their morphologies and failure mechanism. In general, these results are of great importance to the further design and optimisation of metal-polymer joints fabricated using the presented method.