Mechanical heterogeneities in cured structural wood adhesives

Abstract

Wood adhesive bond lines are typically considered chemically and mechanically homogeneous and the occurrence of heterogeneities in cured wood adhesives has rarely been reported in the literature. Nanoindentation, SEM-EDX, and confocal Raman imaging were used to distinguish phases in cured adhesive bond lines that differ in their mechanical and chemical properties. In filler-containing adhesive systems, differences in elastic modulus and chemical composition were revealed that indicated local variations in their filler distribution. Different filtration mechanisms of the wood adherend or porous barriers formed by filler particles are assumed to be responsible for such differences in filler concentration and the particle size between the bulk bond line and the wood–adhesive interphase. The occurrence of such differences shows that assuming the wood bond line as a homogeneous material in the micromechanical modeling of adhesive bonds cannot be generalized.

Keywords:

• Adhesives
• bond line
• mechanical properties
• filler distribution
• nanoindentation
• Raman imaging
• SEM-EDX

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Available upon request: [email protected]

Additional information

Funding

This work was supported by the German Government within the IGF program (AIF, BMWI) [20247 BR] and the “Nachwachsende Rohstoffe program” (FNR, BMEL) [22002918].