Numerical Analysis of a Thick-Adherend Lap Shear Specimen

Abstract

A finite element stress analysis of a thick-adherend lap shear specimen to determine the adhesive shear properties is performed. Key problems associated with this test specimen include the non-uniformity of adhesive stress fields, load eccentricity effects and other less well-characterized mechanics. The numerical model, validated by comparing with the moiré experiment, is proposed for investigation of these problems. Full-field non-uniform stress distributions in the test region are presented. The obtained adhesive shear stress distributions are compared with those from the moiré experiment and the classical theoretical solutions. It is shown that the present two-dimensional solutions agree well with experimental solutions while the theoretical solutions based on simple assumptions differ from those from the numerical and experimental analyses. Load eccentricity encountered in the experimental tests is investigated. It is shown that load eccentricity greatly affects the adhesive shear stress distributions, but not the stress state at the center point of the bond line. Thus, load eccentricity effects would cause large data scatter in adhesive shear modulus and strength measurement. The effect of the adhesive/adherend elastic modulus ratio on the adhesive stress distributions is also investigated. Correction factors accounting for non-uniformity of the adhesive shear stress distributions are determined and used to determine the adhesive shear modulus from the experimental data.