Bonding performance optimization of homogeneous and hybrid hardwood CLT using the Taguchi experimental design method

The favorable properties of the available hardwood resources in Appalachia make them predestined for various high-value-added products. Between them we find mass timber products also, however, the utilization of hardwood species for such construction products comes with several new challenges. Among these, one of the most crucial issues to overcome is ensuring adequate bonding strength and durability. This research aims to optimize the bonding performance of red oak (RO) and red oak-yellow poplar (RO-YP) hybrid Cross-Laminated Timber (CLT), utilizing a one-component polyurethane (1-C PUR) adhesive an surface pretreatment with a primer. For optimization, the Taguchi method was utilized to quantify the effect of four factors, the primer ‘s concentration, adhesive spread rate, clamping pressure buildup time, and clamping pressure on delamination and shear strength across various layup combinations. The focus predominantly rests on mitigating delamination, as the analysis revealed that shear strength and wood failure manifested no notable variance across the investigated settings. Optimal manufacturing parameters’ setup values were identified, significantly diminishing the delamination rates below established thresholds for both YP and RO-YP hybrid panels. The homogenous RO CLT specimens alone remained above the desired level after optimization. The research concludes by outlining specific optimal settings for each wood combination, offering valuable insights for improving CLT bonding efficacy. These findings not only enhance the understanding of adhesive behaviors in hardwood CLTs but also propose practical guidelines for manufacturing, potentially aiding in the broader adoption and application of such materials in construction. • The effect of the primer concentration, adhesive spread, press closure time, and pressure were investigated. • Primer concentration affected mostly the YP – YP and RO – YP bond line delamination. • In the case of the RO-RO bond line, the clamping pressure had the greatest influence. • Different technology parameter levels provide the optimum adhesion performance for each adherend combination. • The slow stepwise press closing is beneficial in each YP adherend combination.