Secondary bending in multi fastener, composite-to-aluminium single shear lap joints

A novel technique to study secondary bending due to the eccentric load path in single shear, composite-to-aluminium lap joints has been developed and used in a parametric study. The method is based on the specimen curvature, which is derived from lateral displacements of the surface. The lateral displacements are measured with an optical measurement system or calculated with the finite element method. It was found that the specimen curvature is equivalent to the secondary bending which is usually measured with strain gauges in the vicinity of the bolt holes. The two most important parameters affecting specimen curvature is the overlap length and the thickness of the aluminium plate in the joints.