Analysis of manufacturing parameters on the shear strength of aluminium/GFRP co-cured and adhesively bonded single-lap joints

Abstract

Due to the increased application of composite materials in recent years, the process of joining composites to metals has become a key area of interest. As a result, methods to increase the strength of composite-to-metal joints are highly sought after. Since the mechanical behaviour of composite-to-metal joints depends on many manufacturing parameters. An experimental and numerical study into the shear strength behaviour of GFRP-to-aluminium single-lap joints was performed to investigate the effect of four manufacturing parameters, with the aim of optimising shear strength. For one manufacturing parameter, a relatively new joining process, co-curing, is studied, and results are benchmarked against secondary (adhesively) bonded joints. The results of this study provides a better understanding of the co-curing process which will increase the application of co-curing in industry. From the results, an increase in adherend (or substrate) thickness and surface roughness were found to increase joint strength. For certain manufacturing configurations, co-cured joints were similar in strength to adhesively bonded ones. The failure mechanism of the co-cured and adhesively bonded single-lap joints was discussed using stress distributions obtained from finite element analysis (FEA) and fractography. It was found that the failure mechanism of co-cured lap joints was cohesive failure by delamination at the first ply layer of the composite adherend. Adhesively bonded joints failed by a mixture of cohesive failure with peel. Results of this study present how the co-cured joining method can be regarded as a highly efficient manufacturing process, which can be tailored to match the strength of traditional joining methods.