Assessment of sandwich beam in three-point bending for measuring adhesive shear modulus

A finite element analysis (FEA) was conducted to examine the feasibility of determining the shear modulus of an adhesive in a bonded geometry using a three-point bending rest on a sandwich beam specimen. The FEA results were compared with the predictions from two analytical solutions for the geometr y used to determine the impact of the assumptions that were made in these a nalyses. The analytical results showed significantly different to the value s obtained from other experiments on bulk samples of the adhesive in the gl assy region. Although there were some agreements in rubbery region, the neg ligible sensitivity of the beam stiffness to the presence of adhesive layer makes the agreements very questionable. To examine the possible explanatio ns for these differences in glassy adhesives, sensitivity analysis was cond ucted to explore the effects of experimental variables. Some possible reaso ns fbr the differences are discussed, but none of these reasons taken alone satisfactorily account for the discrepancies, Until an explanation is foun d, the three-point bending test using a sandwich beam specimen to determine the adhesive shear modulus might not be a desirable test method, at least for the range of geometry examined in this study.