Modelling the Material Resistance of Wood—Part 3: Relative Resistance in above and in Ground Situations—Results of a Global Survey

Durability-based designs with timber require reliable information about the wood properties and how they affect its performance under variable exposure conditions. This study aimed at utilizing a material resistance model (Part 2 of this publication) based on a dose–response approach for predicting the relative decay rates in above-ground situations. Laboratory and field test data were, for the first time, surveyed globally and used to determine material-specific resistance dose values, which were correlated to decay rates. In addition, laboratory indicators were used to adapt the material resistance model to in-ground exposure. The relationship between decay rates in- and above-ground, the predictive power of laboratory indicators to predict such decay rates, and a method for implementing both in a service life prediction tool, were established based on 195 hardwoods, 29 softwoods, 19 modified timbers, and 41 preservative-treated timbers.

The Influence of Thickness on the Tensile Strength of Finnish Birch Veneers under Varying Load Angles

The development of high-performance, veneer-based wood composites is a topic of increasing importance due to the high design flexibility and the comparable mechanical performance to solid wood. Part of this improved mechanical performance can be contributed to the size effect present in wood. Based on previous findings in the literature, this size effect can be either strengthening or weakening. The presented study investigates the influence of thickness and load angle on the tensile strength and tensile stiffness of peeled veneers compared to thin sawn timber. Veneers with thicknesses of 0.5 ± 0.05 mm, 1.0 ± 0.05 mm and 1.5 ± 0.05 mm as well as sawn wood with thicknesses of 1.5 ± 0.1 mm, 3.0 ± 0.1 mm and 5.0 ± 0.1 mm were tested in tension under different load angles (0°, 45° and 90°). The results only partly confirm a size effect for strength parallel to the grain. The strength perpendicular to the grain increased significantly between 0.5 mm and 1.5 mm, with a significant decrease between 1.5 mm and 5.0 mm. The presence of lathe checks diminished the strength perpendicular to the grain of the veneers by about 70% compared to solid wood, partly overshadowing a possible strengthening effect. It was concluded that a transition from a strengthening to a weakening behaviour lies in the range of multiple millimetres, but further investigations are needed to quantify this zone more precisely. The presented results provide a useful basis for the development of veneer-based wood composites with a performance driven layer-thickness.

Improvement of tree growth technology in weakly growing grafting points of apple tree (Malus mill)

This article studies the technology of growing seedlings of different varieties of apples at vegetatively propagated low-growing M-IX and medium-sized MM109 grafting points and provides scientifically based data. Grafting the upper-grafted bud by removing the wooden part resulted in a significant increase in its grip. When apple varieties were grafted to M-IX grafting point without removal of the wood part, the total amount of preserved upper-grafted buds ranged from 76% to 80% by variety, while in the experimental variant of grafting without wood, this figure ranged from 85% to 95% and observed to vary in this interval. When the bud graft is made to the root collar of the grafting point, this figure does not exceed 61.7-68.6% by variety. When the bud was grafted 10 cm above the root collar, it was found to be in the range of 67.5 to 75.9%, respectively.

Combined effect of biological and physical stress on artificial production of agarwood oleoresin in Aquilaria malaccensis

Agarwood is the most expensive wood of the world and highly demanded wood in perfumery industry and ritual ceremonies of various religions. Agarwood is the infectious wood part of Aquilaria tree. Naturally, production of agarwood in Aquilaria takes 10-20 years of time and it can develop only in 1-2% of Aquilaria trees. Different types of biological, chemical and physical methods have been developed for artificial production of agarwood to fulfil the rising demand of the market. In the current article, we tried to explore combined effect of physical and biological stress in the form of stick method to improve agarwood production in Aquilaria malaccensis and compared it with well-known artificial fungal infection syringe method. Total 21 fungal strains were applied alone (syringe method) and with bamboo sticks (stick method). We found maximum infection occurred in stick method by fungi Penicillium polonicum AQGGR1.1 with 10 cm infection length. Artificial induction of marker compounds of agarwood, benzyl acetone and anisyl acetone were measured mostly in stick method, induced by 71.4% fungal strains grown on bamboo sticks, while alone only 42.9% fungi can induced in syringe method. Penicillium aethiopicum AQGGR1.2 found highly agarwood oleoresin inducing fungus in stick method and shown high potential agent in stick method for artificial production of agarwood.

Promotion effect of NP fire retardant pre-treatment on heat-treated poplar wood. Part 1: color generation, dimensional stability, and fire retardancy

Heat treatment (HT) enhances various properties of wood (W), but it takes a relatively long time and WHT is a source of fire hazard. To improve the properties of WHT, Populus beijingensis W. Y. Hsu wood was impregnated with nitrogen-phosphorus (NP) fire retardant (10% aqueous solution) and the effects of the combined NP treatment and HT were observed. Control groups included native wood and samples from WHT200°C, 120 min and WHT220°C, 120 min. The surface color, dimensional stability, and combustion properties of the treated samples were examined. NP pre-treatment intensified the effectivity of HT150°C, where the treatment time decreased by 75%. The decomposition and catalytic dehydration of NP treatment enhanced the dimensional stability and darkened the wood surface. After HT, the NP fire retardant was transformed from dispersive particles into a uniform layer on the inner surfaces of wood. The heat release rate (HRR) decreased by 60.3% and the residual mass (RM) increased by 61.1% in WNP, HT compared to normal WHT200°C poplar.