A numerical study of the shear-strength-predicting capabilities of test specimens for wood–adhesive bonds

The sensitivity to geometrical imperfections of various test methods for wood–adhesive bonds was investigated using nonlinear finite element analysis. The adhesive layers in the specimens were modelled using a nonlinear softening, fracture mechanics model. The specimen types corresponded to the standards according to ASTM-D4680, ASTM-D905, EN-302-1 and a modified version of the ASTM-D3535 specimen. The results show that the prediction of bond line strength is highly dependent on both the specimen type used and adhesive properties such as strength, fracture energy and the shape of the stress-slip behaviour of the adhesive layer. For example, it was shown that the ASTM-D905 specimen was not able to rank the adhesives in terms of local bond line strength in the correct order. Another finding is that the sensitivity to geometrical imperfections and erroneous load application in the test methods is also highly dependent on specimen and adhesive type.