Abstract: Eucalyptus is one of the most fast-growing trees. Therefore, in the last decades it has been extensively planted and harvested so that nowadays Eucalyptus is one of the most popular trees of the planet. There are many genres of this plant and they are often treated as a large bunch of the same timber characterized by moderate mechanical and surface properties which hinder their usage for any sight application (e.g. flooring, cladding, ceiling). In this study four species of Eucalyptus: E. grandis, E. dunnii, E. cloeziana and E. tereticornis were undergone to densification through hydro-thermo-mechanical treatment (HTM) first and then to oil heat-treatment (OHT) in order to improve their mechanical properties and hydrophobicity. It was observed that low density species (E. grandis) reaches higher compression degrees while heavier species (E. tereticornis) reach densities over 800 kg/m³; however, HTM decrease the variability of the properties. Treatments at higher temperature (160 °C) involves higher compression degree, lower set-recovery and higher surface hydrophobization, but also weaker mechanical properties. The hot oil post- treatment helps to contain the springback effect and to reduce the wettability of each specimen. Densified samples present similar surface hardness. The tailored application of the two treatments improves the properties of every Eucalyptus which can gain market also for nobler end-usages.

RESUMO O estudo teve como objetivo avaliar a resistência da madeira de Eucalyptus grandis e Eucalyptus cloeziana submetidas a diferentes condições de umidade a impactos. Para tanto, os corpos de prova foram distribuídos em três condições de umidade (seco, climatizado e saturado). Foram avaliadas as propriedade de resistência a impactos, massa específica e teor de umidade de equilíbrio. Os dados foram interpretados por meio de análise de variância fatorial. Dessa maneira, verificou-se que a madeira de E. cloeziana foi mais resistente a impactos na condição saturada em comparação com as amostras climatizada e seca. Já o E. grandis não apresentou diferença significativa entre as condições de umidade testadas. O E. cloeziana demonstrou maior capacidade de absorver impactos em relação ao E. grandis. Ambas as espécies foram classificadas como pouco resistentes a impactos. Portanto, não é recomendado a utilização das espécies estudadas em locais sujeitos a cargas de choque.

ABSTRACT The study aimed to evaluate the dynamic bending strength of Eucalyptus grandis and Eucalyptus cloeziana woods when subject to different moisture conditions. Samples were divided into three moisture conditions (dry, air-conditioned and wet). The dynamic bending properties, density and equilibrium moisture content were evaluated. The collected data were analyzed through factorial analysis of variance. E. cloeziana wood in the wet condition was more resistant than the dried and air-conditioned samples. On the other hand, dynamic bending strength of E. grandis wood was not significant for the moisture conditions studied. E. cloeziana wood showed higher ability to absorb the impact than E. grandis wood. Both species were classified as low bending strength. Therefore, the use of these species should not be recommended in places with shock loads.