Nathan Kotlarewski

Testing harvested logs is a critical step in the wood products supply chain. Non-destructive evaluation (NDE) methods are essential for grading and sorting logs, especially given variations associated with tree age. In this study, plantation-grown Eucalyptus nitens from two age groups were sourced from two Tasmanian harvesting sites for NDE and comparison with destructive stiffness testing. The key finding is that the correlation between dynamic modulus of elasticity (DMOE) and static modulus of elasticity (MOE) weakens with increasing age, particularly at the whole-log level. For further analysis, the radial location of recovered small clear samples (from pith to bark) was examined. Core samples (near the pith) showed the strongest correlation between DMOE and static MOE (R² = 0.51), followed by middle (R² = 0.46) and outer samples (R² = 0.25). This study demonstrates that considering the radial location of recovered samples is a more effective approach for improving grading accuracy. Age is a key factor for initial segregation of logs before applying NDE for property analysis of both logs and recovered samples.

Eucalyptus nitens (H. Deane & Maiden) Maiden is a widely planted hardwood species in Australia, particularly in Tasmania, where it occupies approximately 168,000 ha. Although primarily managed for pulp production, the species is attracting interest for sawn and engineered wood applications. Previous evaluations of its properties have relied on destructive testing; however, non-destructive evaluation (NDE) techniques provide a viable alternative for industrial applications. This study examined the use of acoustic-based NDE to assess plantation-grown E. nitens logs sourced from two Tasmanian harvesting sites, focusing on the relationship between dynamic modulus of elasticity (DMOE), static MOE, and modulus of rupture (MOR) across radial positions from pith to bark. The results indicated that core samples exhibited stronger correlations with static MOE and MOR compared with middle and outer samples. DMOE consistently overestimated static MOE by 10.81% and 24.66% at the two sites, with variation evident across radial positions. These findings demonstrate the effectiveness of acoustic NDE for evaluating wood stiffness, highlighting the importance of sample location within logs.

Cross-laminated timber (CLT) has become a notable building material due to its structural efficiency, reliability and sustainability. In this study, the bending performance of three-layered CLT constructed from fibre-managed Eucalyptus nitens (E. nitens) was investigated under short-term and long-term loadings. Linear-elastic four-point bending testing was used to determine the maximum serviceability loading capacity before they reached the suggested deflection limits. A pilot study was conducted to investigate the creep behaviour of E. nitens CLT through long-term bending tests in a controlled environmental room. The study suggested that E. nitens CLT has higher serviceability loading capacity and lower creep ratio compared to CLT made from strength-class C24 spruce. The investigations of various configurations of E. nitens CLT panels based on structural grades implemented in top, cross, and bottom layers have revealed different short-term and long-term bending performances. The grade of transverse layers has been found to be the most important factor in improving the bending creep performance of E. nitens CLT. Two modelling equations were employed to perform curve fitting on the experimental creep ratio with time. The conventional power-law modelling tends to underestimate the longer-term creep ratio when compared to a recently developed nonlinear regression modelling equation that takes environmental conditions into account. The mean estimated creep ratio after 50 years was 1.77 for E. nitens CLT, and 1.89 for the C24 spruce CLT. The present study is a pilot investigation to increase the understanding of performance of the newly developed CLT made from fibre-managed plantations E. nitens, with particular emphasis on its creep behaviour. The results of this study provide valuable contributions for future research in this field, and ongoing commercial production of E. nitens CLT.

The mechanical properties of fibre-managed Eucalyptus nitens (E. nitens) cross-laminated timber (CLT) have previously been extensively studied, proving the material to be structurally safe and reliable. However, the vibration performance of CLT manufactured from this relative new construction species is not yet fully understood, especially under different support conditions. In this study, three types of support conditions, including roller–roller, bearer–bearer and clamp–bearer support conditions, were examined under vibration impulse-response testing performed using a simple but effective and repeatable excitation method consisting of a basketball dropped from a known height and an accelerometer. Six three-ply E. nitens CLT panels considered to have different moduli of elasticity in different layers and one strength-class C24 spruce CLT as a controlled reference were included in this study. The results suggest that the fundamental frequency values can effectively reflect the inherent characteristics of CLT panels (bending stiffness and density); however, no obvious relationship was observed between damping ratios and these inherent properties. The values of frequency constant λ₁ were determined to analyse the effect of different support conditions on the values of fundamental frequency. The average values of λ₁ for the roller–roller (9.6) and bearer–bearer (10.1) supports align with the theoretical values (9.87) for simply support (S-S) conditions. However, when clamping loads were applied at one edge of the bearer support, the average values of λ₁ increased up to 10.8 but remained far below the theoretical values for clamped–pinned (C-S) support (15.4).

Abrasion resistance is an important property for the functional performance and serviceability of timber floors. Although hardness is the conventional criterion used in selecting species for flooring applications, it shows greater variations and restricts the use of low-density species, whereas abrasion resistance could generate a more reliable indication of a product’s surface performance. Eucalyptus nitens is a fast-grown global plantation species extensively available in Tasmania, Australia. Until recently, this material has been perceived as unsuitable for appearance applications such as flooring. This study assesses several engineered flooring prototypes comprised of E. nitens—sawlog managed and fibre-managed resources—compared to an existing market product (E. obliqua and a commercial engineered timber flooring product with UV-cured coating). Tests were performed in accordance with the EN 14354:2016, sandpaper method using Taber abraser and further modified to test flooring prototypes. The highest abrasion resistance was observed in the E. nitens veneer composite product. Fibre-managed E. nitens resulted in the greatest level of abrasion, while sawlog-managed E. nitens was comparable to native regrowth E. obliqua, a commonly used flooring species historically used in Australia. Therefore, the findings from this research suggest there are suitable flooring applications for plantation E. nitens as engineered wood products in some domestic and residential dwellings when compared to existing native products.

The performance characteristics of finger-joints as a jointing technique for Eucalyptus nitens is crucial for their use in engineered wood products. This research evaluated the strength of the finger-jointed laminations made from fiber-managed E. nitens. A total of 237 specimens with (117 pieces) and without (120 pieces) finger-joints were sectioned from finger-jointed laminations and tested by bending, tensile, shear, and bearing tests. Bending and tensile tests were paired to identify any correlations. The mean value with finger-joints for bending and tensile were 92.1 MPa and 79.6 MPa, respectively. The presence of finger-joints reduced the strength values. Joint efficiencies in bending and tensile are 0.73 and 0.62, respectively. The distributions of bending and tensile strength were similar for the samples without finger-joints. For the samples with finger-joints, tensile strength was significantly lower than paired bending strength. Shear test results show that the short-span test is inefficient in obtaining the shear strength of fiber-managed E. nitens boards. Meanwhile, the finger-joint efficiency in the bearing is 0.86. The prediction models of lamination’s bending, tensile, and bearing strength were established by non-destructive properties as predictors. Bending strength was highly correlated to the modulus of elasticity value, while tensile and bearing strength were correlated to density. This study obtained promising results on finger-jointed boards from fiber-managed E. nitens suggesting they could be suitable for structural purposes.