Measurement of Shear Modulus and Shear Strength of Adhesives

摘要

This study was conducted to develop an easy - to - use test method suitable for wood adherends, with an accuracy approaching that of the torsion tube method commonly used for metal - bonding adhesives. The simple method would be used to measure the shear stress - strain properties of flexible wood - bonding adhesives. The single lap shear specimen was selected. A review of Goland and Reissner's theory of the stress distributions in single lap joints revealed that a uniform distribution similar to the distribution in a torsion tube can be approached by controlling joint geometry as a function of adhesive rigidity. Results of tests to verify these relationships are reported. A test method is described which incorporates the Goland and Reissner theory. Lap - shear specimens are prepared with the test adhesives using hard maple or steel adherends. The load - deformation properties of the specimens are measured under specific recommended conditions to yield a 'first estimate'' of adhesive shear modulus. This estimate is used to calculate an optimized joint geometry for best attainable uniformity of stress distribution in the joint. The final values for load - deformation properties are then measured under a variety of carefully controlled environmental and experimental conditions. Two unique pieces of equipment, a dual transducer slip gage and an environmental test chamber, were developed to facilitate testing adhesive stress - strain properties. The lap - shear specimen test, it is concluded, is suitable for most adherend - adhesive combinations with ratios of adherend tensile elastic modulus to adhesive shear modulus greater than 300 to 1. (Author abstract modified).