Influence of Adhesive Type on Heat Induced Delamination in Tension Loaded Shear Lap Cross‐Laminated Timber Samples Exposed to Radiant Heat Flux

ABSTRACT Heat induced delamination (HID) is a phenomenon in engineered wood products which may result in the detachment of the bonded timber lamellae before charring propagates to the bond line interphase. This study aims to correlate the thermal degradation of two 1‐c‐polyurethane adhesives at the microscale to the thermo‐hydro‐mechanical behaviour of tension shear lap cross‐laminated timber at an intermediate scale. The performance criteria studied are the failure mode, time to failure and bond line temperature at failure. The variables considered are the adhesive type (standard adhesive [Loctite HB S] and an adhesive with improved elevated temperature performance [Loctite HB X]), initial moisture content and severity of thermal exposure. Results indicate that both adhesive types exhibited HID, with temperatures at failure being influenced by heat flux severity and initial moisture content variations. The study also correlates the thermal degradation with microscale analyses using differential scanning calorimetry (DSC) and dynamic thermo‐mechanical analysis (DTMA).