Comparative Analysis of Bending and Rolling Shear Performance of Poplar and Hybrid Maple–Poplar Cross-Laminated Timber (CLT)

Cross-laminated timber (CLT) is gaining popularity as a sustainable alternative to traditional building materials. However, the decline of natural vegetation and the growth of plantation hardwoods has led the researchers to consider alternatives. This study presents a comparative analysis of bending and rolling shear performance of homogenous poplar (Populus nigra L.) CLT and hybrid CLT, with maple (Acer platanoides L.), in the outer layer and poplar in the core, compared to spruce (Picea abies (L.), H. Karst.) CLT. The CLT panels were prepared using one-component polyurethane (1C-PUR) and melamine adhesive (ME). Poplar CLT exhibited equal or better properties than spruce CLT. The outer maple layer in the hybrid CLT enhanced the global bending modulus (Emg) and bending strength (fm) by 74% and 37%, respectively, due to its higher modulus of elasticity better shear resistance by reducing the cross-layer stress concentrations and rolling shear failure. Additionally, both the adhesive types and wood species significantly influenced the fm, Emg, and rolling shear strength (fr) independently, while their interaction effect was found to be non-significant. The experimental bending stiffness was higher than the theoretical values. The shear analogy method provided the most accurate results for bending and shear strengths, while bending stiffness was best predicted by the modified gamma method, with minor variations. The finite-element models (FEMs) also produced results with a deviation of only 10%.