Earlywood and latewood elastic properties in loblolly pine

Abstract

The elastic properties of earlywood and latewood and their variability were measured in 388 specimens from six loblolly pine trees in a commercial plantation. Properties measured included longitudinal modulus of elasticity, shear modulus, specific gravity, microfibril angle and presence of compression wood. Novel testing procedures were developed to measure properties from specimens of 1 mm=1 mm=30 mm from earlywood or latewood. The elastic properties varied substantially circumferentially around a given ring and this variation was nearly as large as the variation across rings. The elastic properties varied by ring and height, but while the modulus of elasticity increased with height, the shear modulus decreased with height. A strong correlation was found between modulus of elasticity and shear modulus, but only at low heights and inner rings. Specific gravity and microfibril angle were the strongest predictors of elastic properties and explained 75% of the variation in modulus of elasticity for latewood. Despite being the best predictors in this study, these parameters accounted for less than half of the variability of earlywood modulus of elasticity, earlywood shear modulus and latewood shear modulus.

Influence of hot water extraction on cell wall and OSB strand mechanics

“…The MOE derived from nanoindentation was higher than from DMTA due to the fact that the nanoindentation was done in the S2 layer of latewood while DMTA specimens consisted of primarily earlywood. According to Cramer et al (2005), the differences in elastic properties between earlywood and latewood are due to the higher density, lower microfibril angle (MFA), and thicker cell wall of the latter. Larson et al (2001) found that the density of earlywood is around 280 kg/m 3 while latewood is about 600 kg/m 3 .…”

“…Larson et al (2001) found that the density of earlywood is around 280 kg/m 3 while latewood is about 600 kg/m 3 . In addition, Cramer et al (2005) found that elastic properties of earlywood (EW) versus latewood (LW) varied by up to 2.7 (LW/EW). In this experiment, the ratio of LW/EW was 3.0 and 4.2 for aspen and hemlock, respectively (Cramer et al 2005).…”

Variation in Trembling Aspen and White Spruce Wood Quality Grown in Mixed and Single Species Stands in the Boreal Mixedwood Forest

“…It is an important determinant of wood strength and elasticity [31]. Microfibril angle has been shown to explain a large portion of the variation of longitudinal modulus of elasticity (EL) in loblolly pine and Eucalyptus delegatensis R.T. Baker (Evans and Ilic 2001) [32,33]. Cramer et al [32] reported that up to 75% of the variation in EL could be explained by microfibril angle and specific gravity when earlywood and latewood data are combined, while Evans and Ilic [33] report an R 2 of 0.956 relating EL to the ratio of microfibril angle and density.…”

“…Microfibril angle has been shown to explain a large portion of the variation of longitudinal modulus of elasticity (EL) in loblolly pine and Eucalyptus delegatensis R.T. Baker (Evans and Ilic 2001) [32,33]. Cramer et al [32] reported that up to 75% of the variation in EL could be explained by microfibril angle and specific gravity when earlywood and latewood data are combined, while Evans and Ilic [33] report an R 2 of 0.956 relating EL to the ratio of microfibril angle and density. There has been an increase in the recognition of the importance of incorporating wood quality traits in tree improvement programs, however, until recently, microfibril angle has been largely ignored, probably due to the inherent challenges in measuring this trait [31].…”

Determinación de un elemento de volumen representativo de probetas de tablero tensado

“…Al igual que en las propiedades mecánicas obtenidas a macroescala, la nanoindentación también muestra diferencias en estas propiedades entre las células de madera tardía y temprana, siendo las propiedades de estas últimas aproximadamente un 50% menor que las células de madera tardía (Eder et al 2009, Cramer et al 2005, Wimmer et al 1997. Por su parte, Wimmer et al (1997), al estudiar la estructura celular de abeto rojo (Picea rubens), lograron establecer que las capas de la pared celular poseen distintas propiedades mecánicas debido a los cambios en la composición química de éstas.…”