Evaluation of the Singular Stresses in Adhesive Joints

This paper deals with the evaluation of the singularity in the stress field of bonded joints, in particular with the determination of the stress intensity factor. After reviewing the key aspects of the problem, the attention is focussed on establishing a procedure to estimate the stress intensity factor without the need for a detailed finite element analysis of the joints, which typically requires mesh refinement of the order of one-millionth of the adhesive thickness. This is accomplished by means of a numerical procedure to solve the equations of the problem, and is not restricted to a specific geometry and is ready to be implemented also in a personal computer environment. The required boundary conditions are found by a classical structural (monodimensional) solution for the stresses in bonded joints, and are easy to implement as well. The approach is tested for single lap joints, considering a combination of different values of joint parameters (adherend and adhesive thicknesses, overlap length). The results obtained and the involved approximations are examined, and this provides also the opportunity to establish the type of stress that should be considered to obtain the most appropriate definition of the stress intensity factor. (c) Koninklijke Brill NV, Leiden, 2009