Evaluation of the bending properties of novel cross-laminated timber with different configurations made of Australian plantation Eucalyptus nitens using experimental and theoretical methods

Eucalypt species dominate the majority of hardwood plantations in Australia. Although fast-growing eucalypt plantation is not milled commercially for structural purposes due to forestry management procedures applied based on pulp and woodchips production, finding value-added use and developing mass-laminated timber products from this resource could be a sustainable alternate for the timber industries and construction sectors. The objectives of this study were to: (1) evaluate mechanical properties of CLT panel configuration with different combinations of grades from novel species fibre-managed Eucalyptus nitens (E. nitens) and (2) assess the applicability existing theoretical methods developed with typical feedstock and applying dynamic modulus of elasticity (MOEdyn) through acoustic wave velocity (AWV) in those methods to predict the properties of the CLT panels The timber boards graded and laminations were sorted into high, medium and low classes based on static MOE. Based on laminate MOE, twelve, three-layers CLT layups as High-Low-High, Medium-Low-Medium, Medium-Low-High, Medium-High-Medium bonded with polyurethane adhesive were manufactured. The results showed that the bending stiffness and apparent MOE appear to have significant differences among the configurations. The panels with high-grade boards in the top and bottom layers showed the highest average bending stiffness (3.29 × 1011 N.mm2 ) and apparent MOE (15.6 MPa). The panel configuration with the lowest MOE and MOR exceed the loading requirements for performance and commercial application. The collected experimental and numerical results reveal an overall good behaviour of heterogenous hardwood CLT panels and an excellent performance of novel heterogeneous configuration, with a great opportunity on construction applications.. It was also concluded that theoretical prediction using MOEdyn through AWV with an average accuracy of 96%, could be a potential method to evaluate the mechanical properties of the heterogeneous E. nitens CLT panel without mechanical testing. The heterogenous hardwood panel demonstrates a great opportunity for the employment of locally grown timber species for structurally efficient CLT panels. The results of this study an important insight into developing the high-value Australian-made CLT from pulpwood E. nitens timber resource.