Industrial imaging and sensing

Wood quality

The variable quality of fast grown and short rotation plantation wood is proving to be an issue around the world.  The principal issues are large tree-to-tree variations in elastic modulus, and in many cases variations of it with radius within the tree.

Both have a direct link to the fibre type within the wood.  Low modulus leads to a downgrading of much of the  wood from high value, structural use, to low value “industrial” wood, such as pallets, while the second, gradients of fibre-type inside the sawn wood, lead to warp and twist in service.

Wood stiffness can be quite accurately predicted early in the production chain by measuring the speed of elastic waves.

With this in mind, IRL developed the Hitman tool, marketed now by Fibre-gen Ltd, which allows logs to be sorted in the forest and routed appropriately.  Variations of the techniques have been used to account for radial variations within logs so that timber can be sawn to achieve higher value returns, and to allow laboratory testing of small wood samples for tree-breeding purposes.

The fibre types and orientations underlying these wood traits were found to be measurable using tracheid scatter, the characteristic oval shaped patch of light aligned preferentially along the wood fibres (tracheids)  when illuminated by a small laser spot.  Scanning sawn wood with a laser gives maps of fibre type and orientation which hold the key to the prediction of how the timber will warp as it dries.

The light-guiding along the tracheids has been used in an instrument (the Spiralometer) that measures the extent to which the grain spirals around the tree centre.  For the first time, this allowed thousands of trees to be measured and assessed for this major twist-generating defect using cores sampled from growing trees.