Evaluation of non-destructive techniques and visual assessments of grade fibre-grown Eucalyptus logs for structural products

Eucalypt plantations occur worldwide, occupying almost 22 million hectares of land. These plantations are predominantly managed for fibre-based products, and their use for other product types is of increasing interest. While native forest eucalypt material is mainly sawn for timber for appearance application, the potential use of a plantation-based resource for structural products is currently being investigated.

Structural products require stiff forest material and the timber industry may exploit advantageously Non-Destructive Techniques (NDT) to identify the timber qualities most suited for these products.

Adequate studies are needed to support the use of NDT as segregation tools and evaluate their potential to reliably indicate important wood quality variables.

To support better integration of NDT into the segregation of the resource for preferred uses, a study was conducted in a fibre-managed Eucalyptus nitens plantation in Tasmania, Australia. Forty trees were assessed with NDT acoustic techniques, harvested and bucked to sawlog lengths. Logs were measured and evaluated with both acoustic resonance techniques and by visual assessments. Positive and significant correlations were found between the tree and the log measurements, while NDT measures on logs were correlated with visual features.

Results highlight the potential for the integration of visual grading and NDT testing for assessing plantation eucalypt logs and batching them into quality classes according to their characteristics. An accurate classification of the material would support a more efficient use of a low-grade resource which might satisfy different markets such as that for structural Engineered Wood Products (EWP).