The relationship between grain angle and wood properties has not been focus of researches in wood industry. The aim of this study was to establish grain angle variations in commercialEucalyptuslogs and their effects on physical-mechanical wood properties. Wood maximum angular deviation (MAD) was correlated with density, volumetric shrinkage, compressive strength parallel to grain, flexural strength and stiffness as determined by bending and acoustic methods in wood of sevenEucalyptus grandis × Eucalyptus urophyllaclones at 13 years old. The relationship between MAD at pith-bark and base-top positions and its effect on the physical and mechanical properties were evaluated. Amplitude of MAD values was small for the seven clones, and the mean was 6.2°. The grain deviation decreased by only 8% in base-top direction, and the correlations among MAD and three logs heights were small and negative (r = −0.13). MAD values presented an increasing trend of 33% in pith-bark direction, with a small positive correlation (r = 0.42). Basic density (BD) presented a significant correlation with the MAD (r = 26). There was no significant correlation between the MAD and volumetric shrinkage, mechanical properties and modulus of elasticity dynamic (determined by stress wave timer, ultrasound or transverse vibration).

Eucalyptus-based glued laminated timber (glulam) was produced to determine the feasibility of a non-destructive method (drilling resistance) to predict the properties of structural elements and add value to lower-quality hardwood species. Glulam was manufactured with formaldehyde (Resorcinol), reference condition, and bio-based (Castor oil-based) adhesives in two assembly schemes, the core composed either of two continuous lamellae each 105 cm long, or of two formed by the juxtaposition of shorter boards (35 and 55 cm). The shear strength of the glue line (f_v0), modulus of elasticity (E_c90), and strength (f_c90) in compression perpendicular to the grain; delamination (DL); and main and extended glue line thicknesses were evaluated. The Resistograph equipment was used to perform the perforation perpendicular to the glue line (samples extracted from the glulam elements) to correlate the properties. The results of this research demonstrate that the scheme of the boards had little effect on the physical and mechanical properties evaluated (except the main glue line and delamination), and the drilling resistance (DR) presents a significant correlation with practically all properties evaluated (variations in density values and other properties are explained by variations in DR values), making it possible to estimate E_c90 and f_c90 with desired precision (R²_adj ≈ 80%). This highlights the feasibility of using this methodology in the quality control of glulam elements. It is concluded that regardless of the adhesive, elements comprising a 105 cm-length core and external lamellae (T1 and control) are indicated for external use, presenting low delamination. Short-length central lamellae adhesively glued with PUR (T2) are not recommended for external applications due to their susceptibility to delamination. However, T2 is indicated for internal environments due to its low production cost. This study also proved the efficiency of using models based on drilling resistance to estimate wood density and its resistance to compression perpendicular to the fiber.

Eucalyptus-based glued laminated timber (glulam) was produced to determine the feasibility of a non-destructive method (drilling resistance) to predict the properties of structural elements and add value to low-value hardwood species. Glulam was manufactured with both formaldehyde and bio-based adhesives in two assembly schemes. The shear strength of the glue line (f_v0), compression perpendicular to grain (E_c90 and f_c90), delamination (DL), main and extended glue lines thicknesses were evaluated. Our findings indicated that the assembly schemes did not statistically influence properties and linear regression models adjusted for drilling resistance satisfactorily estimated the E_c90 and f_c90.