Adhesive Tensile Strengths of Scarf and Butt Joints of Steel Plates : 1st Report, A Case of Brittle Adhesive

Abstract

Adhesive tensile strengths, o f scarf joints with various scar f angles and butt joints with various adhesive layer thicknesses have been measured to establish fracture criterion for joints of steel plates bonded by brittle epoxy adhesive. A three-dimensional elastic stress analysis of these joints was performed by FEM. Fractures of both joints were explained quantitatively by introducing a boundary layer depth of 0.035 mm at free surfaces of adhesive layers and obeying maximum principal stress criterion. In adhesive layers of scarf joints with 0.1 mm layer thickness, the boundary layer depth of 0.035 mm included most of stress concentrated area at free surfaces. Locations of fracture initiation and fracture modes of adhesive layers observed with an optical microscope and a scanning electron microscope agreed with those expected from stress distributions and boundary layer conception.