Analytical and numerical investigation of bending moment coefficient in unbalanced single lap joints

A study was conducted to investigate the bending moment coefficient in unbalanced boron/epoxy–aluminium single lap joints subjected to tensile loading. It is well known that the main feature of the single lap joint is the eccentric loading path, which results in large deflections of the outer adherend and the overlap. In addition, the joint edge moment or bending moment coefficient at the end of the overlap is a significant feature. Four different overlap lengths (13, 20, 30 and 40 mm) have been analysed. A geometrically non-linear, two-dimensional finite element analysis was also performed to provide useful comparisons with the theoretical analysis. The analytical results mainly proved that, as the overlap length increases, the bending moment coefficient mainly decreased at the stiffer adherend, while the maximum l/c ratio is also decreased. The latter conclusions show that unbalanced (asymmetrical) single lap joints should be designed and manufactured with extreme care.