Variation of nominal adhesive strength specified in JIS with respect to adhesive dimensions and joint geometry

The Japanese Industrial Standard (JIS) defines adhesive strength as the ultimate nominal tensile stress measured using small specimens, without considering the effects of stress concentration. This study therefore examines the reduction in nominal adhesive strength for large adhesive areas in both butt and lap joints. The discussion is framed in terms of adhesive strength expressed as a constant Intensity of the Singular Stress Field (ISSF). Numerical simulations show that the JIS-defined nominal strength varies with both adherend thickness and adhesive length in lap joints, whereas in butt joints it depends primarily on adhesive thickness. By accounting for the influence of specimen geometry on the ISSF, the average adhesive strengths of butt and lap joints are compared across a wide range of adhesive areas.