Abstract:Natural fibres are studied as alternatives for man-made fibres to reinforce composites while keeping the weight lower. The assessment of the value of some commonly available tropical fibres for the composite industry starts with the determination of the strength, E-modulus and strain to failure through single fibre tensile tests. The mean strength and standard deviation is calculated following the normal and Weibull distribution resulting in the questionable benefit of applying the Weibull distribution. Furthermore, a correction method assesses the real fibre elongation from the measured clamp displacement. This procedure seems to be useful for strong, brittle fibres to produce more reliable results for the E-modulus and strain to failure.

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Wood-plastic composites (WPCs) are increasingly used in decking applications, where exterior exposure can lead to sufficient moisture for fungal deterioration. Standard tests recommended to assess fungal durability of WPC, but initially developed for wood or woodbased panels, are not applied in this study because the similarity in moisture behaviour for wood (-based panels) and WPC is questioned. The moisture dynamics of commercialised WPC versus wood-based panels were studied employing different moistening methods. The moisture sorption differences between various WPCs were minimal despite different wood contents, particle sizes, and plastics employed, but given sufficient time WPC wood particles gained sufficient water for fungal decay. To assay fungal durability of WPCs, immersion of the specimens for at least 1 week in water at 70°C seems to be the most effective pretreatment.

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Sustainable use is essential to guarantee future availability of wood. Structural and chemical mapping can contribute to fit-for-purpose usage, as accurate and detailed knowledge of the material enables guided utilization and optimal performance of wood. The platform presented in this paper, illustrated on poplar disks for early selection, collects data in the NIR, visual and X-ray spectrum in maximum 30 min per wood disk. Flatbed scanning proves to be a cheap and fast technique to evaluate basic physical properties such as cross-sectional area and wood density. X-ray CT scanning is used for density mapping adding information on density variation between and within disks. Chemometric modeling of infrared spectra is used to map density, tension wood and lignin content. X-ray- and NIR-based density mapping showed good correlation, although NIR-based maps do not show the same level of detail as X-ray images do due to lower resolution. Results of NIR-based hyperspectral mapping illustrate that tension wood zones were denser and contained less lignin which corresponds with the existence of the G-layer described in the literature. In all, the combination of high-end tools together with simple tools such as flatbed scanning allows for high-throughput and high-resolution quantitative mapping of some of the main properties of poplar wood. Furthermore, infrared scanning can be used to map density, tension wood and chemistry without the need for more complex, expensive and/or time-consuming methods, yet with less accuracy and lower resolution, thus being applicable as single tool for breeding selection

Context: Customers have limited tolerances for colour differences between oak wood elements in parquetry or furniture, whereas manufacturers are in need of an objective method to communicate possible differences in their products. Aims: This study aimed at grading oak wood boards in objectively defined colour classes in correspondence with the visual assessment by an expert panel. Methods: First the most suitable spectrophotometer for measurements approximating the perception of the human eye was selected. Then three colour grading algorithms were evaluated: one based on the smallest distance towards the centre of the colour subspaces, the second using a classification tree and the last implementing the CIEDE2000 colour difference formula to determine tolerance ellipsoids. Results: Statistical analysis using a classification tree and CIEDE2000 tolerance ellipsoids classified the specimens in good accordance with visual assessment, with a 6% and 5% misclassification respectively. Conclusions: The colour grading methodology can be adapted to particular grading purposes and is proposed as a basis for development of an inline colour grading system to be added to commonly used defect detection scanners