Delaminierungseigenschaften und Scherfestigkeiten von verklebten rotkernigen Buchenholzlamellen

The paper deals with investigations on dry shear strength and delamination behavior of gluelines between beech wood laminations showing no or distinct red heartwood. The investigations covered 36 parameter combinations comprising besides the red heartwood two widths of the laminations, two different adhesive families and two delamination procedures related to verification of adhesive type I or II. The tests revealed no influence of red heartwood on shear strength which for all parameter combinations exceeded almost throughout 10 N/mm². In contrary thereto the delamination tests revealed a distinct dependency of the glueline integrity on red heartwood and width of the adherents. No parameter combination conformed to the requirements of adhesive type I. In case of laminations without red heartwood the requirements of adhesive type II were met. Gluelines between two laminations with red heartwood showed throughout very pronounced delamination above 50%. The integrity of gluelines versus delamination represents one of the essential normative requirements for adhesives used in glued load bearing wooden elements. This proof was not possible for gluelines of beech wood laminations with red heartwood when applying today’s European delamination test procedures and performance requirements developed and established for gluelines of softwood laminations.