Damage and failure characteristics of CFRP/aluminum single lap joints designed for lightweight applications

In this study, a full-factorial experimental design was employed for evaluating mechanical behavior of riveted, adhesively bonded and hybrid joints. The effects of significant design factors including overlap length, rivet diameter and adhesive thickness on progressive failure process of CFRP/Al6061-T6 single lap joints under quasi-static loads were investigated using high speed imaging technique. The complex strain distributions were evaluated using digital image correlation method. Results showed that load-displacement curves and failure process of hybrid joints presented two stages to prevent premature joint failure. Final failure mechanisms of hybrid joints were significantly affected by rivet diameter, while independent on overlap length and adhesive thickness. Various types of failure including severe adhesive and cohesive failure, fiber-tear failure and rivet fracture were found on damaged surfaces of hybrid joints using 3.0 mm diameter rivet, while joints using 5.0 mm diameter rivet were featured with flexural fracture of CFRP substrate.