Derivation of the shear modulus on the adhesive layer measured by digital image correlation: study on the tensile shear tests of wood-based materials with veneer

Abstract In this study, peeling veneers of Japanese cedar and Japanese larch were parallel or cross laminated, respectively, and tensile shear tests were conducted. As a result, for Japanese cedar veneers, significant difference in shear strength was found between parallel and cross lamination. On the other hand, for Japanese larch veneers, there was no significant difference in shear strength between different laminate directions. During the shear tests, the strain distribution was measured using Digital Image Correlation. The visualization of principal strain showed that in cross laminated specimens of Japanese cedar, the principal strain was observed around the lathe checks of veneer in the cross layers. Thus, lower shear strength for cross laminated specimens was considered to be due to this strain concentration, which opened the lathe checks and caused the rolling shear failure. Conversely, in cross laminated specimens of Japanese larch, principal strain was not observed as much as in Japanese cedar. Therefore, for Japanese larch, the failure modes were similar for cross and parallel lamination, suggesting that there was no significant difference in the shear strength. In addition, the shear strain on the adhesive layer of the specimen was measured and the shear modulus of the adhesive layer ( G adh ) was derived by determining the shear stress–strain curve. The shear stress–strain curve was determined using convergence calculations presented in existing literature. The results showed that parallel laminated specimens had higher G adh than cross laminated specimens for both wood species. Furthermore, the G adh of cross laminated specimens were between the commonly known shear modulus of the radial section and the transverse section.