Hiroaki Isono

A study and evaluation of the shear strength of adhesive layers subjected to impact loads

Experimental equipment was developed in order to measure easily the shear strength of adhesive layers subjected to impact loads. The stress state of an adhesive joint was calculated with the finite element method (FEM). The results calculated from the FEM were compared with those from experiments conducted with the equipment. It was shown that the fracture behaviour of the joint depended on the level of the incident stress wave. When loading a comparatively high incident stress, the adhesive layer fractures mainly with the shear stress. It is considered that the maximum shear stress measured is the shear strength under impact loads. In order to confirm the validity of this evaluation method, the maximum shear stress was compared with the impact shear strength, which was measured using a cylindrical butt joint subjected to impact torsional loads. Both values accorded well. From this we were able to conclude that the shear strength of the adhesive layer subjected to impact loads could be evaluated with this equipment.

Effect of Adherend Material Stiffness and Geometrical Stiffness on Strength of Adhesively Bonded Joints.

The effect of adherend stiffness on the joint strength is examined by varying the adherend material and varying aspect ratio of the adherend dimension. The joint type used in this study is a stepped-lap bonded joint. The joint materials are three kinds of metals, carbon steel, brass and aluminum alloy, for the adherends and an epoxy resin for the adhesive. The relationship between the Youngs modulus of the adherend material and strength of the joint is experimentally investigated. The joint strengths, i.e., initial failure strength and final fracture strengh are predicted by applying our adhesion criteria on a proposed FEM model. Both upper and lower bounds on the predicted final fracture strength is obtained. And these predicted strengths show good agreement with the experimental results.