Torsion apparatus for measuring shear properties of adhesive bonded joints

Abstract

A napkin-ring torsion apparatus for the study of the shear properties of adhesive bonded joints is described. A high sensitivity capacitance-type extensometer is used for measuring the load-deformation characteristics of the adhesives. Angle of twist sensitivities as high as 6 × 10⁻⁸ radians can reliably be achieved. Shear stress is determined by using an extensometer to measure the strain developed in the metal adherends. The technique has been used with a variety of adhesive materials, having several glue-line thicknesses. Experimental variables include test temperature, strain rate, time at load and time between load-unload cycles.